MediaWiki3D - User contributions [en]

Main Page

2025-12-04T07:48:51Z

OpenDEM 1:

= Prototype for textured and animated 3D models =
<iframe src="https://mediawiki3d.org/model-viewer-logo.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>
* [https://mediawiki3d.org/index.php/Special:NewFiles?user=&mediatype%5B%5D=3D&start=&end=&wpFormIdentifier=specialnewimages&limit=50&offset=:NewFiles Gallery of 3D models]
* [[Articles_Gallery|Gallery of articles with 3D content ]]

Currently, only the glTF 2.0 specification is supported (.glb files). Extensions such as KTX compression or MeshOpts are not yet available.

<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>

== Background ==

Wikimedia Commons currently only supports colorless, untextured 3D models, which only show the basic geometric shape of objects. This page tracks the progress towards adding support for 3D formats capable of full-color, textured 3D models—i.e. where images of the surface appearance are overlaid onto the 3D shapes to provide a more realistic and detailed appearance. Animated 3D models can illustrate how objects or processes change over time, making dynamic developments clearer than static 3D models. By integrating the time axis, they enrich understanding of historical evolution, scientific transformations, or mechanical functions in motion. This page also contains a list of resources and links to get involved, as well as some example 3D models that would fit on Commons once such support is in place.

'''''3D models have been supported in Wikimedia Commons since 2018, but only the STL format can be used at the moment. STL is a format designed for 3D printing that does not support textures, color, and more nuanced digital representation.'''''

To edit this Wiki, [[Special:Userlogin|log in]] using your Wikipedia user account. Use [[Special:Import]] if you want to import a page from Wikipedia.
== Motivation ==

The current issues surrounding Sketchfab show how important a non-commercial platform for sharing and visualising textured 3D models would be: thus there is significant urgency due to current developments. Tens of thousands of 3D models under free licences are under threat, and in a petition to Sketchfab it is said that "this is the virtual equivalent of burning the Library of Alexandria". [https://www.change.org/p/keep-sketchfab-alive-preserve-open-access-to-3d-art-museum-collections Here] is a petition with lots of background information.

== Further information ==

Please take a look at our wiki page [https://commons.wikimedia.org/wiki/Commons:Textured_3D Commons:Textured_3D].

[https://t.me/+tMgoJxx8D7I5NTQ8 ''3D in Wikimedia'' Telegram Channel] - The place to be for current information and discussion

== License information ==
* Animated Wikipedia GIF CC-BY-SA OmegaTombuş
* Animated Tectonic Plates Collide Loop CC-BY-SA LasquetiSpice
* MEDIAWIKI3D Testing Logo CC-BY-SA Dndrnmn1-2Years

Main Page

2025-12-03T17:39:37Z

OpenDEM 1:

Main Page

2025-12-03T17:27:39Z

OpenDEM 1:

= Prototype for textured and animated 3D models =
<iframe src="https://mediawiki3d.org/model-viewer-logo.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>
* [https://mediawiki3d.org/index.php/Special:NewFiles Gallery of 3D models]
* [[Articles_Gallery|Gallery of articles with 3D content ]]

Currently, only the glTF 2.0 specification is supported (.glb files). Extensions such as KTX compression or MeshOpts are not yet available.

<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>

== Background ==

Wikimedia Commons currently only supports colorless, untextured 3D models, which only show the basic geometric shape of objects. This page tracks the progress towards adding support for 3D formats capable of full-color, textured 3D models—i.e. where images of the surface appearance are overlaid onto the 3D shapes to provide a more realistic and detailed appearance. Animated 3D models can illustrate how objects or processes change over time, making dynamic developments clearer than static 3D models. By integrating the time axis, they enrich understanding of historical evolution, scientific transformations, or mechanical functions in motion. This page also contains a list of resources and links to get involved, as well as some example 3D models that would fit on Commons once such support is in place.

'''''3D models have been supported in Wikimedia Commons since 2018, but only the STL format can be used at the moment. STL is a format designed for 3D printing that does not support textures, color, and more nuanced digital representation.'''''

To edit this Wiki, [[Special:Userlogin|log in]] using your Wikipedia user account. Use [[Special:Import]] if you want to import a page from Wikipedia.
== Motivation ==

The current issues surrounding Sketchfab show how important a non-commercial platform for sharing and visualising textured 3D models would be: thus there is significant urgency due to current developments. Tens of thousands of 3D models under free licences are under threat, and in a petition to Sketchfab it is said that "this is the virtual equivalent of burning the Library of Alexandria". [https://www.change.org/p/keep-sketchfab-alive-preserve-open-access-to-3d-art-museum-collections Here] is a petition with lots of background information.

== Further information ==

Please take a look at our wiki page [https://commons.wikimedia.org/wiki/Commons:Textured_3D Commons:Textured_3D].

[https://t.me/+tMgoJxx8D7I5NTQ8 ''3D in Wikimedia'' Telegram Channel] - The place to be for current information and discussion

== License information ==
* Animated Wikipedia GIF CC-BY-SA OmegaTombuş
* Animated Tectonic Plates Collide Loop CC-BY-SA LasquetiSpice

Main Page

2025-12-03T17:26:22Z

OpenDEM 1:

= Prototype for textured and animated 3D models =
<iframe src="https://mediawiki3d.org/model-viewer-logo.html" allowfullscreen style="height:320px; width:100%; border:none;"></iframe>
* [https://mediawiki3d.org/index.php/Special:NewFiles Gallery of 3D models]
* [[Articles_Gallery|Gallery of articles with 3D content ]]

Currently, only the glTF 2.0 specification is supported (.glb files). Extensions such as KTX compression or MeshOpts are not yet available.

<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>

== Background ==

Wikimedia Commons currently only supports colorless, untextured 3D models, which only show the basic geometric shape of objects. This page tracks the progress towards adding support for 3D formats capable of full-color, textured 3D models—i.e. where images of the surface appearance are overlaid onto the 3D shapes to provide a more realistic and detailed appearance. Animated 3D models can illustrate how objects or processes change over time, making dynamic developments clearer than static 3D models. By integrating the time axis, they enrich understanding of historical evolution, scientific transformations, or mechanical functions in motion. This page also contains a list of resources and links to get involved, as well as some example 3D models that would fit on Commons once such support is in place.

'''''3D models have been supported in Wikimedia Commons since 2018, but only the STL format can be used at the moment. STL is a format designed for 3D printing that does not support textures, color, and more nuanced digital representation.'''''

To edit this Wiki, [[Special:Userlogin|log in]] using your Wikipedia user account. Use [[Special:Import]] if you want to import a page from Wikipedia.
== Motivation ==

The current issues surrounding Sketchfab show how important a non-commercial platform for sharing and visualising textured 3D models would be: thus there is significant urgency due to current developments. Tens of thousands of 3D models under free licences are under threat, and in a petition to Sketchfab it is said that "this is the virtual equivalent of burning the Library of Alexandria". [https://www.change.org/p/keep-sketchfab-alive-preserve-open-access-to-3d-art-museum-collections Here] is a petition with lots of background information.

== Further information ==

Please take a look at our wiki page [https://commons.wikimedia.org/wiki/Commons:Textured_3D Commons:Textured_3D].

[https://t.me/+tMgoJxx8D7I5NTQ8 ''3D in Wikimedia'' Telegram Channel] - The place to be for current information and discussion

== License information ==
* Animated Wikipedia GIF CC-BY-SA OmegaTombuş
* Animated Tectonic Plates Collide Loop CC-BY-SA LasquetiSpice

Main Page

2025-12-03T17:25:50Z

OpenDEM 1:

= Prototype for textured and animated 3D models =
<iframe src="https://mediawiki3d.org/model-viewer-logo.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>
* [https://mediawiki3d.org/index.php/Special:NewFiles Gallery of 3D models]
* [[Articles_Gallery|Gallery of articles with 3D content ]]

Currently, only the glTF 2.0 specification is supported (.glb files). Extensions such as KTX compression or MeshOpts are not yet available.

<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>

== Background ==

Wikimedia Commons currently only supports colorless, untextured 3D models, which only show the basic geometric shape of objects. This page tracks the progress towards adding support for 3D formats capable of full-color, textured 3D models—i.e. where images of the surface appearance are overlaid onto the 3D shapes to provide a more realistic and detailed appearance. Animated 3D models can illustrate how objects or processes change over time, making dynamic developments clearer than static 3D models. By integrating the time axis, they enrich understanding of historical evolution, scientific transformations, or mechanical functions in motion. This page also contains a list of resources and links to get involved, as well as some example 3D models that would fit on Commons once such support is in place.

'''''3D models have been supported in Wikimedia Commons since 2018, but only the STL format can be used at the moment. STL is a format designed for 3D printing that does not support textures, color, and more nuanced digital representation.'''''

To edit this Wiki, [[Special:Userlogin|log in]] using your Wikipedia user account. Use [[Special:Import]] if you want to import a page from Wikipedia.
== Motivation ==

The current issues surrounding Sketchfab show how important a non-commercial platform for sharing and visualising textured 3D models would be: thus there is significant urgency due to current developments. Tens of thousands of 3D models under free licences are under threat, and in a petition to Sketchfab it is said that "this is the virtual equivalent of burning the Library of Alexandria". [https://www.change.org/p/keep-sketchfab-alive-preserve-open-access-to-3d-art-museum-collections Here] is a petition with lots of background information.

== Further information ==

Please take a look at our wiki page [https://commons.wikimedia.org/wiki/Commons:Textured_3D Commons:Textured_3D].

[https://t.me/+tMgoJxx8D7I5NTQ8 ''3D in Wikimedia'' Telegram Channel] - The place to be for current information and discussion

== License information ==
* Animated Wikipedia GIF CC-BY-SA OmegaTombuş
* Animated Tectonic Plates Collide Loop CC-BY-SA LasquetiSpice

Main Page

2025-12-03T17:22:57Z

OpenDEM 1:

= Prototype for textured and animated 3D models =
<iframe src="https://mediawiki3d.org/model-viewer_logo.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>
* [https://mediawiki3d.org/index.php/Special:NewFiles Gallery of 3D models]
* [[Articles_Gallery|Gallery of articles with 3D content ]]

Currently, only the glTF 2.0 specification is supported (.glb files). Extensions such as KTX compression or MeshOpts are not yet available.

<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>

== Background ==

Wikimedia Commons currently only supports colorless, untextured 3D models, which only show the basic geometric shape of objects. This page tracks the progress towards adding support for 3D formats capable of full-color, textured 3D models—i.e. where images of the surface appearance are overlaid onto the 3D shapes to provide a more realistic and detailed appearance. Animated 3D models can illustrate how objects or processes change over time, making dynamic developments clearer than static 3D models. By integrating the time axis, they enrich understanding of historical evolution, scientific transformations, or mechanical functions in motion. This page also contains a list of resources and links to get involved, as well as some example 3D models that would fit on Commons once such support is in place.

'''''3D models have been supported in Wikimedia Commons since 2018, but only the STL format can be used at the moment. STL is a format designed for 3D printing that does not support textures, color, and more nuanced digital representation.'''''

To edit this Wiki, [[Special:Userlogin|log in]] using your Wikipedia user account. Use [[Special:Import]] if you want to import a page from Wikipedia.
== Motivation ==

The current issues surrounding Sketchfab show how important a non-commercial platform for sharing and visualising textured 3D models would be: thus there is significant urgency due to current developments. Tens of thousands of 3D models under free licences are under threat, and in a petition to Sketchfab it is said that "this is the virtual equivalent of burning the Library of Alexandria". [https://www.change.org/p/keep-sketchfab-alive-preserve-open-access-to-3d-art-museum-collections Here] is a petition with lots of background information.

== Further information ==

Please take a look at our wiki page [https://commons.wikimedia.org/wiki/Commons:Textured_3D Commons:Textured_3D].

[https://t.me/+tMgoJxx8D7I5NTQ8 ''3D in Wikimedia'' Telegram Channel] - The place to be for current information and discussion

== License information ==
* Animated Wikipedia GIF CC-BY-SA OmegaTombuş
* Animated Tectonic Plates Collide Loop CC-BY-SA LasquetiSpice

Main Page

2025-12-03T17:22:39Z

OpenDEM 1:

= Prototype for textured and animated 3D models =
<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>
* [https://mediawiki3d.org/index.php/Special:NewFiles Gallery of 3D models]
* [[Articles_Gallery|Gallery of articles with 3D content ]]

Currently, only the glTF 2.0 specification is supported (.glb files). Extensions such as KTX compression or MeshOpts are not yet available.

<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>

== Background ==

Wikimedia Commons currently only supports colorless, untextured 3D models, which only show the basic geometric shape of objects. This page tracks the progress towards adding support for 3D formats capable of full-color, textured 3D models—i.e. where images of the surface appearance are overlaid onto the 3D shapes to provide a more realistic and detailed appearance. Animated 3D models can illustrate how objects or processes change over time, making dynamic developments clearer than static 3D models. By integrating the time axis, they enrich understanding of historical evolution, scientific transformations, or mechanical functions in motion. This page also contains a list of resources and links to get involved, as well as some example 3D models that would fit on Commons once such support is in place.

'''''3D models have been supported in Wikimedia Commons since 2018, but only the STL format can be used at the moment. STL is a format designed for 3D printing that does not support textures, color, and more nuanced digital representation.'''''

To edit this Wiki, [[Special:Userlogin|log in]] using your Wikipedia user account. Use [[Special:Import]] if you want to import a page from Wikipedia.
== Motivation ==

The current issues surrounding Sketchfab show how important a non-commercial platform for sharing and visualising textured 3D models would be: thus there is significant urgency due to current developments. Tens of thousands of 3D models under free licences are under threat, and in a petition to Sketchfab it is said that "this is the virtual equivalent of burning the Library of Alexandria". [https://www.change.org/p/keep-sketchfab-alive-preserve-open-access-to-3d-art-museum-collections Here] is a petition with lots of background information.

== Further information ==

Please take a look at our wiki page [https://commons.wikimedia.org/wiki/Commons:Textured_3D Commons:Textured_3D].

[https://t.me/+tMgoJxx8D7I5NTQ8 ''3D in Wikimedia'' Telegram Channel] - The place to be for current information and discussion

== License information ==
* Animated Wikipedia GIF CC-BY-SA OmegaTombuş
* Animated Tectonic Plates Collide Loop CC-BY-SA LasquetiSpice

File:MinecraftBlockbenchMediawiki3DOpt.glb

2025-12-03T17:03:22Z

OpenDEM 1: Uploaded a work by Dndrnmn1-2Years from https://mediawiki3d.org with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{br|1=Logo in Minecraft style.}}
|date=2025-10-20
|source=https://mediawiki3d.org
|author=Dndrnmn1-2Years
|permission=
|other versions=
}}

=={{int:license-header}}==
{{cc-by-4.0}}

Main Page

2025-08-26T18:44:32Z

OpenDEM 1:

= Prototype for textured and animated 3D models =

* [https://mediawiki3d.org/index.php/Special:NewFiles Gallery of 3D models]
* [[Articles_Gallery|Gallery of articles with 3D content ]]

Currently, only the glTF 2.0 specification is supported (.glb files). Extensions such as KTX compression or MeshOpts are not yet available.

<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>

== Background ==

Wikimedia Commons currently only supports colorless, untextured 3D models, which only show the basic geometric shape of objects. This page tracks the progress towards adding support for 3D formats capable of full-color, textured 3D models—i.e. where images of the surface appearance are overlaid onto the 3D shapes to provide a more realistic and detailed appearance. Animated 3D models can illustrate how objects or processes change over time, making dynamic developments clearer than static 3D models. By integrating the time axis, they enrich understanding of historical evolution, scientific transformations, or mechanical functions in motion. This page also contains a list of resources and links to get involved, as well as some example 3D models that would fit on Commons once such support is in place.

'''''3D models have been supported in Wikimedia Commons since 2018, but only the STL format can be used at the moment. STL is a format designed for 3D printing that does not support textures, color, and more nuanced digital representation.'''''

To edit this Wiki, [[Special:Userlogin|log in]] using your Wikipedia user account. Use [[Special:Import]] if you want to import a page from Wikipedia.
== Motivation ==

The current issues surrounding Sketchfab show how important a non-commercial platform for sharing and visualising textured 3D models would be: thus there is significant urgency due to current developments. Tens of thousands of 3D models under free licences are under threat, and in a petition to Sketchfab it is said that "this is the virtual equivalent of burning the Library of Alexandria". [https://www.change.org/p/keep-sketchfab-alive-preserve-open-access-to-3d-art-museum-collections Here] is a petition with lots of background information.

== Further information ==

Please take a look at our wiki page [https://commons.wikimedia.org/wiki/Commons:Textured_3D Commons:Textured_3D].

[https://t.me/+tMgoJxx8D7I5NTQ8 ''3D in Wikimedia'' Telegram Channel] - The place to be for current information and discussion

== License information ==
* Animated Wikipedia GIF CC-BY-SA OmegaTombuş
* Animated Tectonic Plates Collide Loop CC-BY-SA LasquetiSpice

Main Page

2025-08-26T18:16:46Z

OpenDEM 1:

= Prototype for textured and animated 3D models =

* [https://mediawiki3d.org/index.php/Special:NewFiles Gallery of 3D models]
* [[Articles_Gallery|Gallery of articles with 3D content ]]

Currently, only the glTF 2.0 specification is supported (.glb files). Extensions such as KTX compression or MeshOpts are not yet available.

<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>

== Background ==

Wikimedia Commons currently only supports colorless, untextured 3D models, which only show the basic geometric shape of objects. This page tracks the progress towards adding support for 3D formats capable of full-color, textured 3D models—i.e. where images of the surface appearance are overlaid onto the 3D shapes to provide a more realistic and detailed appearance. This page also contains a list of resources and links to get involved, as well as some example 3D models that would fit on Commons once such support is in place.

'''''3D models have been supported in Wikimedia Commons since 2018, but only the STL format can be used at the moment. STL is a format designed for 3D printing that does not support textures, color, and more nuanced digital representation.'''''

To edit this Wiki, [[Special:Userlogin|log in]] using your Wikipedia user account. Use [[Special:Import]] if you want to import a page from Wikipedia.
== Motivation ==

The current issues surrounding Sketchfab show how important a non-commercial platform for sharing and visualising textured 3D models would be: thus there is significant urgency due to current developments. Tens of thousands of 3D models under free licences are under threat, and in a petition to Sketchfab it is said that "this is the virtual equivalent of burning the Library of Alexandria". [https://www.change.org/p/keep-sketchfab-alive-preserve-open-access-to-3d-art-museum-collections Here] is a petition with lots of background information.

== Further information ==

Please take a look at our wiki page [https://commons.wikimedia.org/wiki/Commons:Textured_3D Commons:Textured_3D].

[https://t.me/+tMgoJxx8D7I5NTQ8 ''3D in Wikimedia'' Telegram Channel] - The place to be for current information and discussion

== License information ==
* Animated Wikipedia GIF CC-BY-SA OmegaTombuş
* Animated Tectonic Plates Collide Loop CC-BY-SA LasquetiSpice

Main Page

2025-08-26T17:08:13Z

OpenDEM 1: added an eyecatcher

= Under Construction: Prototype for textured 3D models =

* [https://mediawiki3d.org/index.php/Special:NewFiles Gallery of 3D models]
* [[Articles_Gallery|Gallery of articles with 3D content ]]

Currently, only the glTF 2.0 specification is supported (.glb files). Extensions such as KTX compression or MeshOpts are not yet available.

<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:420px; width:100%; border:none;"></iframe>

== Background ==

Wikimedia Commons currently only supports colorless, untextured 3D models, which only show the basic geometric shape of objects. This page tracks the progress towards adding support for 3D formats capable of full-color, textured 3D models—i.e. where images of the surface appearance are overlaid onto the 3D shapes to provide a more realistic and detailed appearance. This page also contains a list of resources and links to get involved, as well as some example 3D models that would fit on Commons once such support is in place.

'''''3D models have been supported in Wikimedia Commons since 2018, but only the STL format can be used at the moment. STL is a format designed for 3D printing that does not support textures, color, and more nuanced digital representation.'''''

To edit this Wiki, [[Special:Userlogin|log in]] using your Wikipedia user account. Use [[Special:Import]] if you want to import a page from Wikipedia.
== Motivation ==

The current issues surrounding Sketchfab show how important a non-commercial platform for sharing and visualising textured 3D models would be: thus there is significant urgency due to current developments. Tens of thousands of 3D models under free licences are under threat, and in a petition to Sketchfab it is said that "this is the virtual equivalent of burning the Library of Alexandria". [https://www.change.org/p/keep-sketchfab-alive-preserve-open-access-to-3d-art-museum-collections Here] is a petition with lots of background information.

== Further information ==

Please take a look at our wiki page [https://commons.wikimedia.org/wiki/Commons:Textured_3D Commons:Textured_3D].

[https://t.me/+tMgoJxx8D7I5NTQ8 ''3D in Wikimedia'' Telegram Channel] - The place to be for current information and discussion

== License information ==
* Animated Wikipedia GIF CC-BY-SA OmegaTombuş
* Animated Tectonic Plates Collide Loop CC-BY-SA LasquetiSpice

Test

2025-08-26T17:04:31Z

OpenDEM 1:

test

<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:800px; width:100%; border:none;">???</iframe>

Test

2025-08-26T16:54:38Z

OpenDEM 1:

test

<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:800px; width:100%; border:none;">???</iframe>

Test

2025-08-26T16:53:50Z

OpenDEM 1:

test

<iframe src="https://mediawiki3d.org/model-viewer.html" allowfullscreen style="height:800px; width:100%; border:none;"></iframe>

Test

2025-08-26T16:51:03Z

OpenDEM 1: Created page with "test"

test

Tesseract

2025-08-25T16:34:09Z

OpenDEM 1:

{{short description|Four-dimensional analogue of the cube}}
{{about|the geometric shape}}
[[File:Tesseract.glb|thumb|3D model of tesseract]]
{{Infobox polychoron
| Name=Tesseract 8-cell (4-cube)
| Image_File=8-cell-simple.gif
| Type=[[Convex regular 4-polytope]]
| Family=[[Hypercubes]]
| Last=[[Omnitruncated 5-cell|9]]
| Index=10
| Next=[[Rectified tesseract|11]]
| Schläfli={4,3,3} t0,3{4,3,2} or {4,3}×{ } t0,2{4,2,4} or {4}×{4} t0,2,3{4,2,2} or {4}×{ }×{ } t0,1,2,3{2,2,2} or { }×{ }×{ }×{ }
| CD={{CDD|node_1|4|node|3|node|3|node}} {{CDD|node_1|4|node|3|node|2|node_1}} {{CDD|node_1|4|node|2|node_1|4|node}} {{CDD|node_1|4|node|2|node_1|2|node_1}} {{CDD|node_1|2|node_1|2|node_1|2|node_1}}
| Cell_List=8 [[cube|{4,3}]] [[File:Hexahedron.png|20px]]
| Face_List=24 [[Square (geometry)|{4}]]
| Edge_Count=32
| Vertex_Count=16
| Petrie_Polygon=[[octagon]]
| Coxeter_Group=B4, [3,3,4]
| Vertex_Figure=[[File:8-cell verf.svg|80px]] [[Tetrahedron]]
| Dual=[[16-cell]]
| Property_List=[[Convex polytope|convex]], [[isogonal figure|isogonal]], [[isotoxal figure|isotoxal]], [[isohedral figure|isohedral]], [[Hanner polytope]]
}}
{{wikt | tesseract}}
[[File:8-cell net.png|thumb|The [[Dali cross|Dalí cross]], a [[Net (polyhedron)|net]] of a tesseract]]
[[File:Net of tesseract.gif|thumb|The tesseract can be unfolded into eight cubes into 3D space, just as the cube can be unfolded into six squares into 2D space.]]

In [[geometry]], a '''tesseract''' or '''4-cube''' is a [[four-dimensional space|four-dimensional]] [[hypercube]], analogous to a two-[[dimension]]al [[square (geometry)|square]] and a three-dimensional [[cube]].<ref>{{Cite web|title= The Tesseract - a 4-dimensional cube|url= https://www.cut-the-knot.org/ctk/Tesseract.shtml|access-date= 2020-11-09|website= www.cut-the-knot.org}}</ref> Just as the perimeter of the square consists of four edges and the surface of the cube consists of six square [[Face (geometry) |faces]], the [[hypersurface]] of the tesseract consists of eight cubical [[cell (geometry) |cells]], meeting at [[right angle]]s. The tesseract is one of the six [[convex regular 4-polytope]]s.

The tesseract is also called an '''8-cell''', '''C8''', (regular) '''octachoron''', or '''cubic prism'''. It is the four-dimensional '''measure polytope''', taken as a unit for hypervolume.<ref>{{Cite book |last=Elte |first=E. L. |author-link=Emanuel Lodewijk Elte |title=The Semiregular Polytopes of the Hyperspaces |date=2005 |publisher=University of Groningen |isbn=1-4181-7968-X |location=Groningen }}</ref> [[Harold Scott MacDonald Coxeter| Coxeter]] labels it the {{math|''γ''4}} polytope.{{Sfn|Coxeter|1973|pp=122-123|loc=§7.2. illustration Fig 7.2C}} The term ''hypercube'' without a dimension reference is frequently treated as a synonym for this specific [[polytope]].

The ''[[Oxford English Dictionary]]'' traces the word ''tesseract'' to [[Charles Howard Hinton]]'s 1888 book ''[[A New Era of Thought]]''. The term derives from the [[Ancient Greek| Greek]] {{lang|grc-Latn|téssara}} ({{wikt-lang|grc|τέσσαρα}} 'four') and {{lang|grc-Latn|aktís}} ({{wikt-lang|grc|ἀκτίς}} 'ray'), referring to the four edges from each vertex to other vertices. Hinton originally spelled the word as ''tessaract''.<ref>
{{cite OED|term=tesseract|ID=199669}}</ref>

== Geometry ==
As a [[regular polytope]] with three [[cube]]s folded together around every edge, it has [[Schläfli symbol]] {4,3,3} with [[Hyperoctahedral group#By dimension|hyperoctahedral symmetry]] of order 384. Constructed as a 4D [[hyperprism]] made of two parallel cubes, it can be named as a composite Schläfli symbol {4,3} × { }, with symmetry order 96. As a 4-4 [[duoprism]], a [[Cartesian product]] of two [[Square (geometry)|squares]], it can be named by a composite Schläfli symbol {4}×{4}, with symmetry order 64. As an [[orthotope]] it can be represented by composite Schläfli symbol { } × { } × { } × { } or { }4, with symmetry order 16.

Since each vertex of a tesseract is adjacent to four edges, the [[vertex figure]] of the tesseract is a regular [[tetrahedron]]. The [[dual polytope]] of the tesseract is the [[16-cell]] with Schläfli symbol {3,3,4}, with which it can be combined to form the compound of tesseract and 16-cell.

Each edge of a regular tesseract is of the same length. This is of interest when using tesseracts as the basis for a [[network topology]] to link multiple processors in [[parallel computing]]: the distance between two nodes is at most 4 and there are many different paths to allow weight balancing.

A tesseract is bounded by eight three-dimensional [[hyperplane]]s. Each pair of non-parallel hyperplanes intersects to form 24 square faces. Three cubes and three squares intersect at each edge. There are four cubes, six squares, and four edges meeting at every vertex. All in all, a tesseract consists of 8 cubes, 24 squares, 32 edges, and 16 vertices.

===Coordinates===

A ''unit tesseract'' has side length {{math|1}}, and is typically taken as the basic unit for [[hypervolume]] in 4-dimensional space. ''The'' unit tesseract in a [[Cartesian coordinate system]] for 4-dimensional space has two opposite vertices at coordinates {{math|[0, 0, 0, 0]}} and {{math|[1, 1, 1, 1]}}, and other vertices with coordinates at all possible combinations of {{math|0}}s and {{math|1}}s. It is the [[Cartesian product]] of the closed [[unit interval]] {{math|[0, 1]}} in each axis.

Sometimes a unit tesseract is centered at the origin, so that its coordinates are the more symmetrical <math>\bigl({\pm\tfrac12}, \pm\tfrac12, \pm\tfrac12, \pm\tfrac12 \bigr).</math> This is the Cartesian product of the closed interval <math>\bigl[{-\tfrac12}, \tfrac12\bigr]</math> in each axis.

Another commonly convenient tesseract is the Cartesian product of the closed interval {{math|[−1, 1]}} in each axis, with vertices at coordinates {{math|(±1, ±1, ±1, ±1)}}. This tesseract has side length 2 and hypervolume {{math|1=24 = 16}}.

===Net===
An unfolding of a [[polytope]] is called a [[Net (polyhedron)|net]]. There are 261 distinct nets of the tesseract.<ref>{{cite web|url=http://unfolding.apperceptual.com/|title=Unfolding an 8-cell|website=Unfolding.apperceptual.com|access-date=21 January 2018}}</ref> The unfoldings of the tesseract can be counted by mapping the nets to ''paired trees'' (a [[Tree (graph theory)|tree]] together with a [[perfect matching]] in its [[Complement graph|complement]]).

Each of the 261 nets can tile 3-space.<ref>[[Matt Parker|Parker, Matt]]. [https://whuts.org/ Which Hypercube Unfoldings Tile Space?] Retrieved 2025 May 11.</ref>

===Construction===
[[File:From Point to Tesseract (Looped Version).gif|thumb|An animation of the shifting in [[dimension]]s]]
The construction of [[hypercube]]s can be imagined the following way:
* '''1-dimensional:''' Two points A and B can be connected to become a line, giving a new line segment AB.
* '''2-dimensional:''' Two parallel line segments AB and CD separated by a distance of AB can be connected to become a square, with the corners marked as ABCD.
* '''3-dimensional:''' Two parallel squares ABCD and EFGH separated by a distance of AB can be connected to become a cube, with the corners marked as ABCDEFGH.
* '''4-dimensional:''' Two parallel cubes ABCDEFGH and IJKLMNOP separated by a distance of AB can be connected to become a tesseract, with the corners marked as ABCDEFGHIJKLMNOP. However, this parallel positioning of two cubes such that their 8 corresponding pairs of vertices are each separated by a distance of AB can only be achieved in a space of 4 or more dimensions.
[[File:Dimension levels.svg|480px|A diagram showing how to create a tesseract from a point]]

The 8 cells of the tesseract may be regarded (three different ways) as two interlocked rings of four cubes.{{Sfn|Coxeter|1970|p=18}}

The tesseract can be decomposed into smaller 4-polytopes. It is the convex hull of the compound of two [[Demihypercube|demitesseracts]] ([[Demitesseract|16-cells]]). It can also be [[Point-set triangulation|triangulated]] into 4-dimensional [[simplex|simplices]] ([[5-cell#Irregular 5-cells|irregular 5-cells]]) that share their vertices with the tesseract. It is known that there are {{val|92487256}} such triangulations<ref>{{citation
| last1 = Pournin | first1 = Lionel
| mr = 3038527
| title = The flip-Graph of the 4-dimensional cube is connected
| journal = [[Discrete & Computational Geometry]]
| pages = 511–530
| volume = 49
| year = 2013
| issue = 3
| doi = 10.1007/s00454-013-9488-y| arxiv = 1201.6543| s2cid = 30946324
}}
</ref> and that the fewest 4-dimensional simplices in any of them is 16.<ref>{{citation
| last1 = Cottle | first1 = Richard W.
| mr = 676709
| title = Minimal triangulation of the 4-cube
| journal = [[Discrete Mathematics (journal)|Discrete Mathematics]]
| pages = 25–29
| volume = 40
| year = 1982
| doi = 10.1016/0012-365X(82)90185-6| doi-access = free
}}</ref>

The dissection of the tesseract into instances of its [[Orthoscheme#Characteristic simplex of the general regular polytope|characteristic simplex]] (a particular [[orthoscheme]] with Coxeter diagram {{CDD|node|4|node|3|node|3|node}}) is the most basic direct construction of the tesseract possible. The '''[[5-cell#Orthoschemes|characteristic 5-cell of the 4-cube]]''' is a [[fundamental region]] of the tesseract's defining [[Coxeter group|symmetry group]], the group which generates the [[B4 polytope|B4 polytopes]]. The tesseract's characteristic simplex directly ''generates'' the tesseract through the actions of the group, by reflecting itself in its own bounding facets (its ''mirror walls'').

=== Radial equilateral symmetry ===
The radius of a [[hypersphere]] circumscribed about a regular polytope is the distance from the polytope's center to one of the vertices, and for the tesseract this radius is equal to its edge length; the diameter of the sphere, the length of the diagonal between opposite vertices of the tesseract, is twice the edge length. Only a few uniform [[polytopes]] have this property, including the four-dimensional tesseract and [[24-cell#Radially equilateral honeycomb|24-cell]], the three-dimensional [[Cuboctahedron#Radial equilateral symmetry|cuboctahedron]], and the two-dimensional [[hexagon]]. In particular, the tesseract is the only hypercube (other than a zero-dimensional point) that is ''radially equilateral''. The longest vertex-to-vertex diagonal of an <math>n</math>-dimensional hypercube of unit edge length is <math>\sqrt{n\vphantom{t}},</math> which for the square is <math>\sqrt2,</math> for the cube is <math>\sqrt3,</math> and only for the tesseract is <math>\sqrt4 = 2</math> edge lengths.

An axis-aligned tesseract inscribed in a unit-radius 3-sphere has vertices with coordinates <math>\bigl({\pm\tfrac12}, \pm\tfrac12, \pm\tfrac12, \pm\tfrac12\bigr).</math>

=== Properties {{anchor|Formulas}} ===
{{tesseract_graph_nonplanar_visual_proof.svg|150px|thumb|right}}
For a tesseract with side length {{Mvar|s}}:

* [[Hypervolume]] (4D): <math>H=s^4</math>
* Surface "volume" (3D): <math>SV=8s^3</math>
*[[Face diagonal]]: <math>d_\mathrm{2}=\sqrt{2} s</math>
*[[Space diagonal|Cell diagonal]]: <math>d_\mathrm{3}=\sqrt{3} s</math>
*4-space diagonal: <math>d_\mathrm{4}=2s</math>

=== As a configuration ===
This [[Regular 4-polytope#As configurations|configuration matrix]] represents the tesseract. The rows and columns correspond to vertices, edges, faces, and cells. The diagonal numbers say how many of each element occur in the whole tesseract. The diagonal reduces to the [[f-vector]] (16,32,24,8).

The nondiagonal numbers say how many of the column's element occur in or at the row's element.{{Sfn|Coxeter|1973|loc=§1.8 Configurations|p=12}} For example, the 2 in the first column of the second row indicates that there are 2 vertices in (i.e., at the extremes of) each edge; the 4 in the second column of the first row indicates that 4 edges meet at each vertex.

The bottom row defines they facets, here cubes, have f-vector (8,12,6). The next row left of diagonal is ridge elements (facet of cube), here a square, (4,4).

The upper row is the f-vector of the [[vertex figure]], here tetrahedra, (4,6,4). The next row is vertex figure ridge, here a triangle, (3,3).

<math>\begin{bmatrix}\begin{matrix}16 & 4 & 6 & 4 \\ 2 & 32 & 3 & 3 \\ 4 & 4 & 24 & 2 \\ 8 & 12 & 6 & 8 \end{matrix}\end{bmatrix}</math>

==Projections==
It is possible to project tesseracts into three- and two-dimensional spaces, similarly to projecting a cube into two-dimensional space.

[[File:Orthogonal projection envelopes tesseract.png|thumb|left|Parallel projection envelopes of the tesseract (each cell is drawn with different color faces, inverted cells are undrawn)]]

[[File:Hypercubeorder binary.svg|thumb|right|The [[rhombic dodecahedron]] forms the convex hull of the tesseract's vertex-first parallel-projection. The number of vertices in the layers of this projection is 1 4 6 4 1—the fourth row in [[Pascal's triangle]].]]

The ''cell-first'' parallel [[graphical projection|projection]] of the tesseract into three-dimensional space has a [[cube|cubical]] envelope. The nearest and farthest cells are projected onto the cube, and the remaining six cells are projected onto the six square faces of the cube.

The ''face-first'' parallel projection of the tesseract into three-dimensional space has a [[cuboid]]al envelope. Two pairs of cells project to the upper and lower halves of this envelope, and the four remaining cells project to the side faces.

The ''edge-first'' parallel projection of the tesseract into three-dimensional space has an envelope in the shape of a [[hexagonal prism]]. Six cells project onto rhombic prisms, which are laid out in the hexagonal prism in a way analogous to how the faces of the 3D cube project onto six rhombs in a hexagonal envelope under vertex-first projection. The two remaining cells project onto the prism bases.

The ''vertex-first'' parallel projection of the tesseract into three-dimensional space has a [[rhombic dodecahedron|rhombic dodecahedral]] envelope. Two vertices of the tesseract are projected to the origin. There are exactly two ways of [[dissection (geometry)|dissecting]] a rhombic dodecahedron into four congruent [[rhombohedron|rhombohedra]], giving a total of eight possible rhombohedra, each a projected [[cube]] of the tesseract. This projection is also the one with maximal volume. One set of projection vectors are {{nowrap|1=''u'' = (1,1,−1,−1)}}, {{nowrap|1=''v'' = (−1,1,−1,1)}}, {{nowrap|1=''w'' = (1,−1,−1,1)}}.

{{clear|left}}
[[File:Orthogonal Tesseract Gif.gif|thumb|right|Animation showing each individual cube within the B4 Coxeter plane projection of the tesseract]]

{| class=wikitable
|+ [[Orthographic projection]]s
|- align=center
![[Coxeter plane]]
!B4
!B4 --> A3
!A3
|- align=center
!Graph
|[[File:4-cube t0.svg|150px]]
|[[File:4-4 duoprism-isotoxal.svg|150px]]
|[[File:4-cube t0 A3.svg|150px]]
|- align=center
![[Dihedral symmetry]]
|[8]
|[4]
|[4]
|- align=center
!Coxeter plane
!Other
!B3 / D4 / A2
!B2 / D3
|- align=center
!Graph
|[[File:4-cube column graph.svg|150px]]
|[[File:4-cube t0 B3.svg|150px]]
|[[File:4-cube t0 B2.svg|150px]]
|- align=center
!Dihedral symmetry
|[2]
|[6]
|[4]
|}

{{-}}
{{multiple image
| class=wikitable
| footer = Orthographic projection Coxeter plane B4 graph with [[hidden lines]] as dash lines, and the tesseract without hidden lines.
| image1 = Tesseract_With_Hidden_Dash_Lines.jpg
| image2 = Tesseract_Without_Hidden_Lines.jpg
| total_width = 300px
}}

{{-}}
{| class="wikitable" width=480
|- align=center valign=top
|rowspan=2|[[File:8-cell.gif]] A 3D projection of a tesseract performing a [[SO(4)#Geometry of 4D rotations|simple rotation]] about a plane in 4-dimensional space. The plane bisects the figure from front-left to back-right and top to bottom.
|[[File:8-cell-orig.gif]] A 3D projection of a tesseract performing a [[SO(4)#Geometry of 4D rotations|double rotation]] about two orthogonal planes in 4-dimensional space.
|}
{{-}}
{| class=wikitable width=640
|- align=center valign=top
|[[File:Animation of three four dimensional cube.webm|thumb|3D Projection of three tesseracts with and without faces]]
|[[File:Tesseract-perspective-vertex-first-PSPclarify.png|200px]] Perspective with '''hidden volume elimination'''. The red corner is the nearest in [[Four-dimensional space|4D]] and has 4 cubical cells meeting around it.
|}

{| class=wikitable width=640
|- align=center valign=top
|[[File:Tesseract tetrahedron shadow matrices.svg|200px|right]]
The [[tetrahedron]] forms the [[convex hull]] of the tesseract's vertex-centered central projection. Four of 8 cubic cells are shown. The 16th vertex is projected to [[point at infinity|infinity]] and the four edges to it are not shown.
|[[File:Stereographic polytope 8cell.png|200px]] [[Stereographic projection]] 
(Edges are projected onto the [[3-sphere]])
|}

{| class=wikitable
|- align=left valign=top
|[[File:3D stereographic projection tesseract.PNG|360px]] [[Stereoscopy|Stereoscopic]] 3D projection of a tesseract (parallel view)
|-
|[[File:Hypercube Disarmed.PNG|360px]] [[Stereoscopy|Stereoscopic]] 3D Disarmed [[Hypercube]]
|}

== Tessellation ==
The tesseract, like all [[hypercubes]], [[Tessellation|tessellates]] [[Euclidean space]]. The self-dual [[tesseractic honeycomb]] consisting of 4 tesseracts around each face has [[Ludwig Schläfli|Schläfli]] symbol '''{4,3,3,4}'''. Hence, the tesseract has a [[dihedral angle]] of 90°.{{Sfn|Coxeter|1973|p=293}}

The tesseract's [[#Radial equilateral symmetry|radial equilateral symmetry]] makes its tessellation the [[Tesseractic honeycomb#Sphere packing|unique regular body-centered cubic lattice]] of equal-sized spheres, in any number of dimensions.

== Related polytopes and honeycombs ==
The tesseract is 4th in a series of [[hypercube]]:
{{Hypercube polytopes}}

The tesseract (8-cell) is the third in the sequence of 6 convex regular 4-polytopes (in order of size and complexity).

{{Regular convex 4-polytopes}}

As a uniform [[duoprism]], the tesseract exists in a [[Uniform 4-polytope#Polygonal prismatic prisms: .5Bp.5D .C3.97 .5B .5D .C3.97 .5B .5D|sequence of uniform duoprisms]]: {''p''}×{4}.

The regular tesseract, along with the [[16-cell]], exists in a set of 15 [[Truncated tesseract#Related uniform polytopes in tesseract symmetry|uniform 4-polytopes with the same symmetry]]. The tesseract {4,3,3} exists in a [[Hexagonal tiling honeycomb#Polytopes and honeycombs with tetrahedral vertex figures|sequence of regular 4-polytopes and honeycombs]], {''p'',3,3} with [[tetrahedron|tetrahedral]] [[vertex figure]]s, {3,3}. The tesseract is also in a [[Order-5 cubic honeycomb#Related polytopes and honeycombs with cubic cells|sequence of regular 4-polytope and honeycombs]], {4,3,''p''} with [[cube|cubic]] [[cell (geometry)|cells]].

{| class=wikitable style="float:right;" width=320
!Orthogonal||Perspective
|-
|[[File:4-generalized-2-cube.svg|160px]]
|[[File:Complex polygon 4-4-2-stereographic3.svg|160px]]
|-
|colspan=2|4{4}2, with 16 vertices and 8 4-edges, with the 8 4-edges shown here as 4 red and 4 blue squares
|}
The [[regular complex polytope]] 4{4}2, {{CDD|4node_1|4|node}}, in <math>\mathbb{C}^2</math> has a real representation as a tesseract or 4-4 [[duoprism]] in 4-dimensional space. 4{4}2 has 16 vertices, and 8 4-edges. Its symmetry is 4[4]2, order 32. It also has a lower symmetry construction, {{CDD|4node_1|2|4node_1}}, or 4{}×4{}, with symmetry 4[2]4, order 16. This is the symmetry if the red and blue 4-edges are considered distinct.<ref>Coxeter, H. S. M., ''Regular Complex Polytopes'', second edition, Cambridge University Press, (1991).</ref>

{{Clear}}

==In popular culture==
Since their discovery, four-dimensional hypercubes have been a popular theme in art, architecture, and science fiction. Notable examples include:

* "[[And He Built a Crooked House]]", [[Robert A. Heinlein|Robert Heinlein]]'s 1940 science fiction story featuring a building in the form of a four-dimensional hypercube.<ref>{{citation
|title=Mathematics in Science Fiction: Mathematics as Science Fiction
|first=David
|last=Fowler
|journal=World Literature Today
|volume=84
|issue=3
|year=2010
|pages=48–52
|doi=10.1353/wlt.2010.0188
|jstor=27871086|s2cid=115769478
}}</ref> This and [[Martin Gardner]]'s "The No-Sided Professor", published in 1946, are among the first in science fiction to introduce readers to the [[Moebius band]], the [[Klein bottle]], and the hypercube (tesseract).
* ''[[Crucifixion (Corpus Hypercubus)]]'', a 1954 oil painting by Salvador Dalí featuring a four-dimensional hypercube unfolded into a three-dimensional [[Latin cross]].<ref>{{citation|title=Dali's dimensions|first=Martin|last=Kemp|journal=[[Nature (journal)|Nature]]|volume=391|issue=27|date=1 January 1998|pages=27|doi=10.1038/34063|bibcode=1998Natur.391...27K|s2cid=5317132|doi-access=free}}</ref>
* The [[Grande Arche]], a monument and building near Paris, France, completed in 1989. According to the monument's engineer, [[Erik Reitzel]], the Grande Arche was designed to resemble the projection of a hypercube.<ref>{{citation|last=Ursyn|first=Anna|title=Knowledge Visualization and Visual Literacy in Science Education|publisher=Information Science Reference|year=2016|isbn=9781522504818|pages=91|contribution-url=https://books.google.com/books?id=-JBJDAAAQBAJ&pg=PA91|contribution=Knowledge Visualization and Visual Literacy in Science Education}}</ref>
* ''[[Fez (video game)|Fez]]'', a video game where one plays a character who can see beyond the two dimensions other characters can see, and must use this ability to solve platforming puzzles. Features "Dot", a tesseract who helps the player navigate the world and tells how to use abilities, fitting the theme of seeing beyond human perception of known dimensional space.<ref>{{cite web|url=http://www.giantbomb.com/dot/3005-23100/|title=Dot (Character) - Giant Bomb|website=Giant Bomb|access-date=21 January 2018}}</ref>
The word ''tesseract'' has been adopted for numerous other uses in popular culture, including as a plot device in works of science fiction, often with little or no connection to the four-dimensional hypercube; see [[Tesseract (disambiguation)]].


==Notes==
{{Reflist}}

== References ==
* {{Cite book | last=Coxeter | first=H.S.M. | author-link=Harold Scott MacDonald Coxeter | year=1973 | title=Regular Polytopes | publisher=Dover | place=New York | edition=3rd | title-link=Regular Polytopes (book) | pages=122–123}}
* F. Arthur Sherk, Peter McMullen, Anthony C. Thompson, Asia Ivic Weiss (1995) ''Kaleidoscopes: Selected Writings of H.S.M. Coxeter'', Wiley-Interscience Publication {{isbn|978-0-471-01003-6}} [http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471010030.html]
** (Paper 22) H.S.M. Coxeter, ''Regular and Semi Regular Polytopes I'', [[Mathematische Zeitschrift]] 46 (1940) 380–407, MR 2,10]
** (Paper 23) H.S.M. Coxeter, ''Regular and Semi-Regular Polytopes II'', [Math. Zeit. 188 (1985) 559-591]
** (Paper 24) H.S.M. Coxeter, ''Regular and Semi-Regular Polytopes III'', [Math. Zeit. 200 (1988) 3-45]
* {{Citation | last=Coxeter | first=H.S.M. | author-link=Harold Scott MacDonald Coxeter | year=1970 | title=Twisted Honeycombs | place=Providence, Rhode Island | journal=Conference Board of the Mathematical Sciences Regional Conference Series in Mathematics | publisher=American Mathematical Society | volume=4 }}
* [[John Horton Conway|John H. Conway]], Heidi Burgiel, Chaim Goodman-Strauss (2008) ''The Symmetries of Things'', {{isbn|978-1-56881-220-5}} (Chapter 26. pp. 409: Hemicubes: 1n1)
* [[Thorold Gosset|T. Gosset]] (1900) ''On the Regular and Semi-Regular Figures in Space of n Dimensions'', [[Messenger of Mathematics]], Macmillan.
* {{cite journal
| last = Hall | first = T. Proctor | authorlink = T. Proctor Hall
| year = 1893
| jstor = 2369565
| title = The projection of fourfold figures on a three-flat
| journal = [[American Journal of Mathematics]]
| volume = 15
| issue = 2 | pages = 179–189
| doi = 10.2307/2369565 }}
* [[Norman Johnson (mathematician)|Norman Johnson]] ''Uniform Polytopes'', Manuscript (1991)
** N.W. Johnson: ''The Theory of Uniform Polytopes and Honeycombs'', Ph.D. (1966)
* [[Victor Schlegel]] (1886) ''Ueber Projectionsmodelle der regelmässigen vier-dimensionalen Körper'', Waren.

== External links ==
* {{KlitzingPolytopes|polychora.htm|4D uniform polytopes (polychora)|x4o3o3o - tes}}
* [http://mrl.nyu.edu/~perlin/demox/Hyper.html ken perlin's home page] A way to visualize hypercubes, by [[Ken Perlin]]
* [https://www.math.union.edu/~dpvc/math/4D/ Some Notes on the Fourth Dimension] includes animated tutorials on several different aspects of the tesseract, by [http://www.math.union.edu/~dpvc/ Davide P. Cervone]
* [http://www.fano.co.uk/hypermodel/tesseract.html Tesseract animation with hidden volume elimination]
{{Hypercube polytopes}}
{{Regular 4-polytopes}}
{{Polytopes}}

[[Category:Algebraic topology]]
[[Category:Regular 4-polytopes]]
[[Category:Cubes]]

Articles Gallery

2025-08-25T16:31:00Z

OpenDEM 1:

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3D models of natural landscapes and geological formations provide an immersive way to appreciate the scale and intricate details of Earth’s features. They support educational initiatives in earth sciences and environmental studies by offering intuitive, visual representations.

[[File:Lees_ferry_grand_canyon_arizona.glb|300px|link=Grand_Canyon]]
[[File:Mount_everest_and_mountains_tibet_nepal.glb|300px|link=Mount_Everest]]
[[File:Monument_valley_-_merrick_butte.glb|300px|link=Merrick_Butte]]

== Biology ==
3D models provide a realistic representation of objects, which helps improve understanding of their shape, function, and spatial relationships. This is especially useful for studying organisms, fossils, and anatomical features, where a detailed and accurate visualization can bring insights into its biology and evolution.

[[File:Triceratops.glb|300px|link=Triceratops]]
[[File:Red_Fox_Cranium.glb|300px|link=Red_fox]]
[[File:Bacteriophage.glb|300px|link=Bacteriophage]]

== Mathematics ==
3D models enable precise visualization and analysis of surface geometry, capturing curvature, texture, and topology beyond the limits of 2D representation. Some surfaces, such as the Steiner surface, are hard to visualise without a 3D model.

[[File:Klein_bottle.glb|300px|link=Klein_bottle]]
[[File:Mobius_strips.glb|300px|link=Möbius_strip]]
[[File:Roman.glb|300px|link=Roman_surface]]

Template:Regular 4-polytopes

2025-08-25T16:30:04Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Template:Regular_4-polytopes

{{Navbox with collapsible groups
| name = Regular 4-polytopes
| title = [[Regular 4-polytope]]s
| state = {{{state<includeonly>|autocollapse</includeonly>}}}
| listclass = plainlist

| selected = {{{selected|{{{1|}}}}}}

| section1 = Convex
| abbr1 = Convex
| state1 = <noinclude>expanded</noinclude>
| list1 = {{Navbox with columns|child
| colwidth = 16%
| colstyle = text-align:center;

| col1header = [[5-cell]]
| col1 =
* {3,3,3}
* pentachoron
* 4-simplex

| col2header = [[Tesseract|8-cell]]
| col2 =
* {4,3,3}
* tesseract
* 4-cube

| col3header = [[16-cell]]
| col3 =
* {3,3,4}
* hexadecachoron
* 4-orthoplex

| col4header = [[24-cell]]
| col4 =
* {3,4,3}
* icositetrachoron
* octaplex

| col5header = [[120-cell]]
| col5 =
* {5,3,3}
* hecatonicosachoron
* dodecaplex

| col6header = [[600-cell]]
| col6 =
* {3,3,5}
* hexacosichoron
* tetraplex

}}

| section2 = Star
| abbr2 = Star
| state2 = <noinclude>expanded</noinclude>
| list2 = {{Navbox with columns|child
| colwidth = 10%
| colstyle = text-align:center;

| col1header = [[icosahedral 120-cell|icosahedral 120-cell]]
| col1 =
* {3,5,{{sfrac|5|2}}}
* icosaplex

| col2header = [[small stellated 120-cell|small stellated 120-cell]]
| col2 =
* {{{sfrac|5|2}},5,3}
* stellated dodecaplex

| col3header = [[great 120-cell|great 120-cell]]
| col3 =
* {5,{{sfrac|5|2}},5}
* great dodecaplex

| col4header = [[grand 120-cell|grand 120-cell]]
| col4 =
* {5,3,{{sfrac|5|2}}}
* grand dodecaplex

| col5header = [[great stellated 120-cell|great stellated 120-cell]]
| col5 =
* {{{sfrac|5|2}},3,5}
* great stellated dodecaplex

| col6header = [[grand stellated 120-cell|grand stellated 120-cell]]
| col6 =
* {{{sfrac|5|2}},5,{{sfrac|5|2}}}
* grand stellated dodecaplex

| col7header = [[great grand 120-cell|great grand 120-cell]]
| col7 =
* {5,{{sfrac|5|2}},3}
* great grand dodecaplex

| col8header = [[great icosahedral 120-cell|great icosahedral 120-cell]]
| col8 =
* {3,{{sfrac|5|2}},5}
* great icosaplex

| col9header = [[grand 600-cell|grand 600-cell]]
| col9 =
* {3,3,{{sfrac|5|2}}}
* grand tetraplex

| col10header = [[great grand stellated 120-cell|great grand stellated 120-cell]]
| col10 =
* {{{sfrac|5|2}},3,3}
* great grand stellated dodecaplex

}}

}}<noinclude>
{{Documentation}}
</noinclude>

Template:Infobox polychoron

2025-08-25T16:30:04Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Template:Infobox_polychoron

#REDIRECT [[Template:Infobox 4-polytope]]

{{Redirect category shell|
{{R from move}}
}}

Template:Infobox 4-polytope

2025-08-25T16:30:04Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Template:Infobox_4-polytope

{{Infobox
|bodystyle=
|abovestyle=background:#e7dcc3
|above={{{Name}}}
|image={{#invoke:InfoboxImage|InfoboxImage|image={{{Image_File|}}}|size={{{Image_size|}}}|sizedefault=240px}}
|caption={{{Image_Caption|}}}
|label1=Type
|data1={{{Type|}}}
|label2=[[Schläfli symbol]]
|data2={{{Schläfli|}}}
|label3= [[Coxeter diagram]]
|data3={{{CD|}}}
|label4=[[3-face|Cells]]
|data4={{{Cell_List|}}}
|label5=[[2-face|Faces]]
|data5={{{Face_List|}}}
|label6=[[Edge (geometry)|Edges]]
|data6={{{Edge_Count|}}}
|label7=[[Vertex (geometry)|Vertices]]
|data7={{{Vertex_Count|}}}
|label8=[[Vertex figure]]
|data8={{{Vertex_Figure|}}}
|label9=[[Petrie polygon]]
|data9={{{Petrie_Polygon|}}}
|label10=[[Coxeter group]]
|data10={{{Coxeter_Group|}}}
|label11=[[Coxeter notation|Symmetry group]]
|data11={{{Symmetry_Group|}}}
|label12=[[Dual polytope|Dual]]
|data12={{{Dual|}}}
|label13=Properties
|data13={{{Property_List|}}}
|label14=[[Uniform 4-polytope#Convex uniform 4-polytopes|Uniform index]]
|data14={{{Index|}}}
}}<noinclude>
{{Documentation}}
[[Category:Mathematics infobox templates |4-polytope]]

</noinclude>

Template:Hypercube polytopes

2025-08-25T16:30:04Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Template:Hypercube_polytopes

{| class=wikitable
|+ [[Petrie polygon]] [[orthographic projection]]s
|- align=center
|[[File:1-simplex t0.svg|60px]]
|[[File:2-cube.svg|60px]]
|[[File:3-cube graph.svg|60px]]
|[[File:4-cube graph.svg|60px]]
|[[File:5-cube graph.svg|60px]]
|[[File:6-cube graph.svg|60px]]
|[[File:7-cube graph.svg|60px]]
|[[File:8-cube.svg|60px]]
|[[File:9-cube.svg|60px]]
|[[File:10-cube.svg|60px]]
|- align=center
|[[Line segment]]
|[[Square]]
|[[Cube]]
|[[Tesseract|4-cube]]
|[[5-cube]]
|[[6-cube]]
|[[7-cube]]
|[[8-cube]]
|[[9-cube]]
|[[10-cube]]
|}
<noinclude>
[[Category:Polyhedra and tiling templates]]
</noinclude>

Template:Regular convex 4-polytopes

2025-08-25T16:30:03Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Template:Regular_convex_4-polytopes

{| class="wikitable mw-collapsible {{{collapsestate|mw-collapsed}}}" style="white-space:nowrap;text-align:center;"
!colspan=8|[[Regular 4-polytopes|Regular convex 4-polytopes]] {{#if:{{{radius|}}}|of radius {{{radius|}}}|}}
|-
!style="text-align:right;"|[[Coxeter_group|Symmetry group]]
|[[Tetrahedral symmetry|A4]]
|colspan=2|[[Hyperoctahedral_group|B4]]
|[[F4_(mathematics)|F4]]
|colspan=2|[[H4_polytope|H4]]
|-
!style="vertical-align:top;text-align:right;"|Name
|style="vertical-align:top;"|[[5-cell]] 
Hyper-[[tetrahedron]] 
5-point
|style="vertical-align:top;"|[[16-cell]] 
Hyper-[[octahedron]] 
8-point
|style="vertical-align:top;"|[[8-cell]] 
Hyper-[[cube]] 
16-point
|style="vertical-align:top;"|[[24-cell]] 
 24-point
|style="vertical-align:top;"|[[600-cell]] 
Hyper-[[Regular icosahedron|icosahedron]] 
120-point
|style="vertical-align:top;"|[[120-cell]] 
Hyper-[[Regular dodecahedron|dodecahedron]] 
600-point
|-
!style="text-align:right;"|[[Schläfli symbol]]
|{3, 3, 3}
|{3, 3, 4}
|{4, 3, 3}
|{3, 4, 3}
|{3, 3, 5}
|{5, 3, 3}
|-
!style="text-align:right;"|[[Coxeter diagram|Coxeter mirrors]]
|{{Coxeter–Dynkin diagram|node_1|3|node|3|node|3|node}}
|{{Coxeter–Dynkin diagram|node_1|3|node|3|node|4|node}}
|{{Coxeter–Dynkin diagram|node_1|4|node|3|node|3|node}}
|{{Coxeter–Dynkin diagram|node_1|3|node|4|node|3|node}}
|{{Coxeter–Dynkin diagram|node_1|3|node|3|node|5|node}}
|{{Coxeter–Dynkin diagram|node_1|5|node|3|node|3|node}}
|-
!style="text-align:right;"|Mirror dihedrals
|{{sfrac|𝝅|3}} {{sfrac|𝝅|3}} {{sfrac|𝝅|3}} {{sfrac|𝝅|2}} {{sfrac|𝝅|2}} {{sfrac|𝝅|2}}
|{{sfrac|𝝅|3}} {{sfrac|𝝅|3}} {{sfrac|𝝅|4}} {{sfrac|𝝅|2}} {{sfrac|𝝅|2}} {{sfrac|𝝅|2}}
|{{sfrac|𝝅|4}} {{sfrac|𝝅|3}} {{sfrac|𝝅|3}} {{sfrac|𝝅|2}} {{sfrac|𝝅|2}} {{sfrac|𝝅|2}}
|{{sfrac|𝝅|3}} {{sfrac|𝝅|4}} {{sfrac|𝝅|3}} {{sfrac|𝝅|2}} {{sfrac|𝝅|2}} {{sfrac|𝝅|2}}
|{{sfrac|𝝅|3}} {{sfrac|𝝅|3}} {{sfrac|𝝅|5}} {{sfrac|𝝅|2}} {{sfrac|𝝅|2}} {{sfrac|𝝅|2}}
|{{sfrac|𝝅|5}} {{sfrac|𝝅|3}} {{sfrac|𝝅|3}} {{sfrac|𝝅|2}} {{sfrac|𝝅|2}} {{sfrac|𝝅|2}}
|-
!style="vertical-align:top;text-align:right;"|Graph
|[[Image:4-simplex t0.svg|120px]]
|[[Image:4-cube t3.svg|120px]]
|[[Image:4-cube t0.svg|120px]]
|[[Image:24-cell t0 F4.svg|120px]]
|[[Image:600-cell graph H4.svg|120px]]
|[[Image:120-cell graph H4.svg|120px]]
|-
!style="text-align:right;"|Vertices
|5 tetrahedral
|8 octahedral
|16 tetrahedral
|24 cubical
|120 icosahedral
|600 tetrahedral
|-
!style="vertical-align:top;text-align:right;"|[[120-cell#Chords|Edges]]
|10 triangular
|24 square
|32 triangular
|96 triangular
|720 pentagonal
|1200 triangular
|-
!style="vertical-align:top;text-align:right;"|Faces
|10 triangles
|32 triangles
|24 squares
|96 triangles
|1200 triangles
|720 pentagons
|-
!style="vertical-align:top;text-align:right;"|Cells
|5 tetrahedra
|16 tetrahedra
|8 cubes
|24 octahedra
|600 tetrahedra
|120 dodecahedra
|-
!style="vertical-align:top;text-align:right;"|[[600-cell#Clifford parallel cell rings|Tori]]
|1 [[5-cell#Boerdijk–Coxeter helix|5-tetrahedron]]
|2 [[16-cell#Helical construction|8-tetrahedron]]
|2 [[8-cell#Construction|4-cube]]
|4 [[24-cell#Cell rings|6-octahedron]]
|20 [[600-cell#Boerdijk–Coxeter helix rings|30-tetrahedron]]
|12 [[120-cell#Intertwining rings|10-dodecahedron]]
|-
!style="vertical-align:top;text-align:right;"|Inscribed
|120 in 120-cell
|675 in 120-cell
|2 16-cells
|3 8-cells
|25 24-cells
|10 600-cells
|-
!style="vertical-align:top;text-align:right;"|[[Great circle|Great polygons]]
|
|2 [[16-cell#Coordinates|squares]] x 3
|4 rectangles x 4
|4 [[24-cell#Hexagons|hexagons]] x 4
|12 [[600-cell#Geodesics|decagons]] x 6
|100 [[120-cell#Chords|irregular hexagons]] x 4
|-
!style="vertical-align:top;text-align:right;"|[[Petrie polygon]]s
|1 [[5-cell#Boerdijk–Coxeter helix|pentagon]] x 2
|1 [[16-cell#Helical construction|octagon]] x 3
|2 [[Octagon#Skew octagon|octagon]]s x 4
|2 [[Dodecagon#Skew dodecagon|dodecagon]]s x 4
|4 [[30-gon#Petrie polygons|30-gon]]s x 6
|20 [[30-gon#Petrie polygons|30-gon]]s x 4
|-
!style="vertical-align:top;text-align:right;"|{{#ifeq:{{{radius|}}}|1|[[24-cell#Hexagons|Long radius]]|{{#ifeq:{{{radius|}}}|{{radic|2}}|[[24-cell#Squares|Long radius]]|Long radius}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>1</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\sqrt{2}</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>1</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\sqrt{2}</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>1</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\sqrt{2}</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>1</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\sqrt{2}</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>1</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\sqrt{2}</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>1</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\sqrt{2}</math>}}}}
|-
!style="vertical-align:top;text-align:right;"|Edge length
|{{#ifeq:{{{radius|1}}}|1|<math>\sqrt{\tfrac{5}{2}} \approx 1.581</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\sqrt{5} \approx 2.236</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>\sqrt{2} \approx 1.414</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>2</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>1</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\sqrt{2} \approx 1.414</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>1</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\sqrt{2} \approx 1.414</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>\tfrac{1}{\phi} \approx 0.618</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\tfrac{\sqrt{2}}{\phi} \approx 0.874</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>\tfrac{1}{\phi^2\sqrt{2}} \approx 0.270</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>2-\phi \approx 0.382</math>}}}}
|-
!style="vertical-align:top;text-align:right;"|Short radius
|{{#ifeq:{{{radius|1}}}|1|<math>\tfrac{1}{4}</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\tfrac{\sqrt{2}}{4} \approx 0.354</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>\tfrac{1}{2}</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\tfrac{\sqrt{2}}{2} \approx 0.707</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>\tfrac{1}{2}</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\tfrac{\sqrt{2}}{2} \approx 0.707</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>\sqrt{\tfrac{1}{2}} \approx 0.707</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>1</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>\sqrt{\tfrac{\phi^4}{8}} \approx 0.926</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\sqrt{\tfrac{\phi^4}{4}} \approx 1.309</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>\sqrt{\tfrac{\phi^4}{8}} \approx 0.926</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\sqrt{\tfrac{\phi^4}{4}} \approx 1.309</math>}}}}
|-
!style="vertical-align:top;text-align:right;"|Area
|{{#ifeq:{{{radius|1}}}|1|<math>10\left(\tfrac{5\sqrt{3}}{8}\right) \approx 10.825</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>10\left(\tfrac{5\sqrt{3}}{4}\right) \approx 21.651</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>32\left(\sqrt{\tfrac{3}{4}}\right) \approx 27.713</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>32\left(\sqrt{3}\right) \approx 55.425</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>24</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>48</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>96\left(\sqrt{\tfrac{3}{16}}\right) \approx 41.569</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>96\left(\sqrt{\tfrac{3}{4}}\right) \approx 83.138</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>1200\left(\tfrac{\sqrt{3}}{4\phi^2}\right) \approx 198.48</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>1200\left(\tfrac{2\sqrt{3}}{4\phi^2}\right) \approx 396.95</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>720\left(\tfrac{\sqrt{25+10\sqrt{5}}}{8\phi^4}\right) \approx 90.366</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>720\left(\tfrac{\sqrt{25+10\sqrt{5}}}{4\phi^4}\right) \approx 180.73</math>}}}}
|-
!style="vertical-align:top;text-align:right;"|Volume
|{{#ifeq:{{{radius|1}}}|1|<math>5\left(\tfrac{5\sqrt{5}}{24}\right) \approx 2.329</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>5\left(\tfrac{5\sqrt{10}}{12}\right) \approx 6.588</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>16\left(\tfrac{1}{3}\right) \approx 5.333</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>16\left(\tfrac{2\sqrt{2}}{3}\right) \approx 15.085</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>8</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>8\sqrt{8} \approx 22.627</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>24\left(\tfrac{\sqrt{2}}{3}\right) \approx 11.314</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>24\left(\tfrac{4}{3}\right) = 32</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>600\left(\tfrac{\sqrt{2}}{12\phi^3}\right) \approx 16.693</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>600\left(\tfrac{4}{12\phi^3}\right) \approx 47.214</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>120\left(\tfrac{15 + 7\sqrt{5}}{4\phi^6\sqrt{8}}\right) \approx 18.118</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>120\left(\tfrac{15 + 7\sqrt{5}}{4\phi^6}\right) \approx 51.246</math>}}}}
|-
!style="vertical-align:top;text-align:right;"|4-Content
|{{#ifeq:{{{radius|1}}}|1|<math>\tfrac{\sqrt{5}}{24}\left(\tfrac{\sqrt{5}}{2}\right)^4 \approx 0.146</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\tfrac{\sqrt{5}}{24}\left(\sqrt{5}\right)^4 \approx 2.329</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>\tfrac{2}{3} \approx 0.667</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\tfrac{8}{3} \approx 2.666</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>1</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>4</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>2</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>8</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>\tfrac{\text{Short}\times\text{Vol}}{4} \approx 3.863</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\tfrac{\text{Short}\times\text{Vol}}{4} \approx 15.451</math>}}}}
|{{#ifeq:{{{radius|1}}}|1|<math>\tfrac{\text{Short}\times\text{Vol}}{4} \approx 4.193</math>|{{#ifeq:{{{radius}}}|{{radic|2}}|<math>\tfrac{\text{Short}\times\text{Vol}}{4} \approx 16.770</math>}}}}
|}<noinclude>
[[Category:Geometry templates]]
</noinclude>

Template:Tesseract graph nonplanar visual proof.svg

2025-08-25T16:30:01Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Template:Tesseract_graph_nonplanar_visual_proof.svg

[[File:tesseract_graph_nonplanar_visual_proof.svg|thumb|{{{1|upright}}}|[[Proof without words]] that a [[hypercube graph]] is [[planar_graph|non-planar]] using [[Kuratowski's theorem|Kuratowski's]] or [[Wagner's theorem]]s and finding either ''K''5 (top) or ''K''3,3 (bottom) [[glossary_of_graph_theory#subgraph|subgraphs]] ]]<noinclude>
[[Category:Mathematics image insertion templates]]
</noinclude>

Template:Polytopes

2025-08-25T16:30:01Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Template:Polytopes

{| {{#ifeq:{{{state|}}}|collapsed|class="wikitable mw-collapsible mw-collapsed"|class="wikitable mw-collapsible"}}
|-
!colspan="13" style="background:lightsteelblue;" class=skin-invert|{{navbar-collapsible|Fundamental convex [[regular polytope|regular]] and [[uniform polytope]]s in dimensions 2–10 |Polytopes}}

|- style="text-align:center;"
!style="background:gainsboro;"|[[Coxeter group#Finite Coxeter groups|Family]]
|style="background:gainsboro;"|[[Simple Lie group#A series|{{math|''A''''n''}}]]
|style="background:gainsboro;"|[[Simple Lie group#B series|{{math|''B''''n''}}]]
|style="background:gainsboro;"|{{font color||#f0f0e0|{{math|''I''2(''p'')}} / [[Simple Lie group#D series|{{math|''D''''n''}}]]}}
|style="background:gainsboro;"|{{font color||#f0e0e0|
[[E6 (mathematics)|{{math|''E''6}}]] / [[E7 (mathematics)|{{math|''E''7}}]] / [[E8 (mathematics)|{{math|''E''8}}]]}} / {{font color||#e0f0e0|[[F4 (mathematics)|{{math|''F''4}}]]}} / {{font color||#e0e0f0|[[G2 (mathematics)|{{math|''G''2}}]]}}
|style="background:gainsboro;"| [[H4 (mathematics)|{{math|''H''''n''}}]]

|- style="text-align:center;"
!style="background:gainsboro;"|[[Regular polygon]]
|[[Equilateral triangle|Triangle]]
|[[Square]]
|style="background:#f0f0e0;"|[[regular polygon|p-gon]]
|style="background:#e0e0f0;"| [[Hexagon]]
| [[Pentagon]]
|- style="text-align:center;"
!style="background:gainsboro;" |[[Uniform polyhedron]]
|style=""|[[Tetrahedron]]
|style=""|[[Octahedron]] • [[Cube]]
|style=""|[[Tetrahedron|Demicube]]
|style=""|
|style=""| [[Regular dodecahedron|Dodecahedron]] • [[Regular icosahedron|Icosahedron]]

|- style="text-align:center;"
!style="background:gainsboro;"|[[Uniform polychoron]]
|[[5-cell|Pentachoron]]
|[[16-cell]] • [[Tesseract]]
|[[16-cell|Demitesseract]]
|style="background:#e0f0e0;"| [[24-cell]]
| [[120-cell]] • [[600-cell]]

|- style="text-align:center;"
!style="background:gainsboro;"|[[Uniform 5-polytope]]
|style=""|[[5-simplex]]
|style=""|[[5-orthoplex]] • [[5-cube]]
|style=""|[[5-demicube]]
|style=""|
|style=""|

|- style="text-align:center;"
!style="background:gainsboro;"|[[Uniform 6-polytope]]
|[[6-simplex]]
|[[6-orthoplex]] • [[6-cube]]
|[[6-demicube]]
|style="background:#f0e0e0;"| [[1 22 polytope|122]] • [[2 21 polytope|221]]
|

|- style="text-align:center;"
!style="background:gainsboro;"|[[Uniform 7-polytope]]
|style=""|[[7-simplex]]
|style=""|[[7-orthoplex]] • [[7-cube]]
|style=""|[[7-demicube]]
|style="background:#f0e0e0;"| [[1 32 polytope|132]] • [[2 31 polytope|231]] • [[3 21 polytope|321]]
|style=""|

|- style="text-align:center;"
!style="background:gainsboro;"|[[Uniform 8-polytope]]
|[[8-simplex]]
|[[8-orthoplex]] • [[8-cube]]
|[[8-demicube]]
|style="background:#f0e0e0;"| [[1 42 polytope|142]] • [[2 41 polytope|241]] • [[4 21 polytope|421]]
|

|- style="text-align:center;"
!style="background:gainsboro;"|[[Uniform 9-polytope]]
|style=""|[[9-simplex]]
|style=""|[[9-orthoplex]] • [[9-cube]]
|style=""|[[9-demicube]]
|style=""|
|style=""|

|- style="text-align:center;"
!style="background:gainsboro;"|[[Uniform 10-polytope]]
|[[10-simplex]]
|[[10-orthoplex]] • [[10-cube]]
|[[10-demicube]]
|
|

|- style="text-align:center;"
!style="background:gainsboro;"|Uniform ''n''-[[polytope]]
|style=""|''n''-[[simplex]]
|style=""|''n''-[[Cross-polytope|orthoplex]] • ''n''-[[hypercube|cube]]
|style=""|''n''-[[demihypercube|demicube]]
|style="background:#f0e0e0;"|[[Uniform 1 k2 polytope|1k2]] • [[Uniform 2 k1 polytope|2k1]] • [[Uniform k 21 polytope|k21]]
|style=""|''n''-[[pentagonal polytope]]

|- style="text-align:center;"
!colspan="13" style="background:gainsboro;" class=skin-invert|Topics: [[Polytope families]] • [[Regular polytope]] • [[List of regular polytopes and compounds]] • [[Uniform polytope#Operations|Polytope operations]]
|}<noinclude>{{documentation|content=
==See also==
*{{tl|Honeycombs}}
[[Category:Polytopes]]
[[Category:Geometry navigational boxes]]
}}</noinclude>

Template:KlitzingPolytopes

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{{cite web
|first = Richard
|last = Klitzing
|title = {{{title|{{{2|{{PAGENAMEBASE}}}}}}}} {{{name|{{{3|}}}}}}
|url = https://bendwavy.org/klitzing/{{{rooturl|dimensions}}}/{{{urlname|{{{anchor|{{{1|}}}}}}}}}
|access-date = {{{access-date|{{{accessdate|}}}}}}
|mode={{{mode|}}}
|archive-date = {{{archivedate|{{{archive-date|}}}}}}
|archive-url = {{{archiveurl|{{{archive-url|}}}}}}
|url-status = {{{url-status|}}}
|quote = {{{quote|}}}
}}<noinclude>
{{doc}}
</noinclude>

Module:Coxeter–Dynkin diagram

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-- module to turn a parameter list into a list of [[Coxeter–Dynkin diagram]] images.
-- See the template documentation or any example for how it is used and works.
local p = {}

function p.CDD(frame)
-- For calling from #invoke.
local pframe = frame:getParent()
local args = pframe.args
return p._CDD(args)
end

function p._CDD(args)
-- For calling from other Lua modules.
local body ='' -- create and start the output string
for v, x in ipairs(args) do -- process params, ignoring any names
if (x ~= '') then -- check for null/empty names
body = body .. "[[File:CDel_" .. x .. ".png|class=skin-invert-image|link=]]" -- write file for this parameter
end
end
body = body .. "" -- finish output string
return body -- return result
end

return p

Template:Coxeter–Dynkin diagram

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<includeonly>{{#invoke:Coxeter–Dynkin diagram|CDD}}</includeonly><noinclude>
{{documentation}}
</noinclude>

Template:CDD

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Template:Radic

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{{#if:{{{2|}}}|{{{2|}}}}}√{{{1}}}<noinclude>
{{Deprecated template}}
{{Documentation}}

</noinclude>

Template:Isbn

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<includeonly>{{ safesubst:#if: {{{text|{{{3|}}}}}}
| {{ safesubst:#if: {{{link|}}}
| {{ safesubst:#ifeq: {{{link|}}} | yes
| [[ {{ safesubst:#if:trim | {{{text|{{{3|}}}}}} }}|{{ safesubst:#if:trim | {{{text|{{{3|}}}}}} }}]]
| [[{{{link|}}}|{{ safesubst:#if:trim | {{{text|{{{3|}}}}}} }}]]
}}
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| {{ safesubst:#if: {{{link|}}}
| {{ safesubst:#ifeq: {{{link|}}} | yes
| [[ {{ safesubst:#if:trim | {{{bg|{{{2|}}}}}} }} |{{ safesubst:#if:trim | {{{bg|{{{2|}}}}}} }}]]
| [[ {{ safesubst:#if:trim | {{{link|}}} }} |{{ safesubst:#if:trim | {{{bg|{{{2|}}}}}} }}]]
}}
| {{ safesubst:#if:trim | {{{bg|{{{2|}}}}}} }}
}}
}}</includeonly><noinclude>
{{documentation}}
</noinclude>

Template:Wikt

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{{Redirect category shell|
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}}

Tesseract

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{{short description|Four-dimensional analogue of the cube}}
{{about|the geometric shape}}
{{Infobox polychoron
| Name=Tesseract 8-cell (4-cube)
| Image_File=8-cell-simple.gif
| Type=[[Convex regular 4-polytope]]
| Family=[[Hypercubes]]
| Last=[[Omnitruncated 5-cell|9]]
| Index=10
| Next=[[Rectified tesseract|11]]
| Schläfli={4,3,3} t0,3{4,3,2} or {4,3}×{ } t0,2{4,2,4} or {4}×{4} t0,2,3{4,2,2} or {4}×{ }×{ } t0,1,2,3{2,2,2} or { }×{ }×{ }×{ }
| CD={{CDD|node_1|4|node|3|node|3|node}} {{CDD|node_1|4|node|3|node|2|node_1}} {{CDD|node_1|4|node|2|node_1|4|node}} {{CDD|node_1|4|node|2|node_1|2|node_1}} {{CDD|node_1|2|node_1|2|node_1|2|node_1}}
| Cell_List=8 [[cube|{4,3}]] [[File:Hexahedron.png|20px]]
| Face_List=24 [[Square (geometry)|{4}]]
| Edge_Count=32
| Vertex_Count=16
| Petrie_Polygon=[[octagon]]
| Coxeter_Group=B4, [3,3,4]
| Vertex_Figure=[[File:8-cell verf.svg|80px]] [[Tetrahedron]]
| Dual=[[16-cell]]
| Property_List=[[Convex polytope|convex]], [[isogonal figure|isogonal]], [[isotoxal figure|isotoxal]], [[isohedral figure|isohedral]], [[Hanner polytope]]
}}
{{wikt | tesseract}}
[[File:8-cell net.png|thumb|The [[Dali cross|Dalí cross]], a [[Net (polyhedron)|net]] of a tesseract]]
[[File:Net of tesseract.gif|thumb|The tesseract can be unfolded into eight cubes into 3D space, just as the cube can be unfolded into six squares into 2D space.]]

In [[geometry]], a '''tesseract''' or '''4-cube''' is a [[four-dimensional space|four-dimensional]] [[hypercube]], analogous to a two-[[dimension]]al [[square (geometry)|square]] and a three-dimensional [[cube]].<ref>{{Cite web|title= The Tesseract - a 4-dimensional cube|url= https://www.cut-the-knot.org/ctk/Tesseract.shtml|access-date= 2020-11-09|website= www.cut-the-knot.org}}</ref> Just as the perimeter of the square consists of four edges and the surface of the cube consists of six square [[Face (geometry) |faces]], the [[hypersurface]] of the tesseract consists of eight cubical [[cell (geometry) |cells]], meeting at [[right angle]]s. The tesseract is one of the six [[convex regular 4-polytope]]s.

The tesseract is also called an '''8-cell''', '''C8''', (regular) '''octachoron''', or '''cubic prism'''. It is the four-dimensional '''measure polytope''', taken as a unit for hypervolume.<ref>{{Cite book |last=Elte |first=E. L. |author-link=Emanuel Lodewijk Elte |title=The Semiregular Polytopes of the Hyperspaces |date=2005 |publisher=University of Groningen |isbn=1-4181-7968-X |location=Groningen }}</ref> [[Harold Scott MacDonald Coxeter| Coxeter]] labels it the {{math|''γ''4}} polytope.{{Sfn|Coxeter|1973|pp=122-123|loc=§7.2. illustration Fig 7.2C}} The term ''hypercube'' without a dimension reference is frequently treated as a synonym for this specific [[polytope]].

The ''[[Oxford English Dictionary]]'' traces the word ''tesseract'' to [[Charles Howard Hinton]]'s 1888 book ''[[A New Era of Thought]]''. The term derives from the [[Ancient Greek| Greek]] {{lang|grc-Latn|téssara}} ({{wikt-lang|grc|τέσσαρα}} 'four') and {{lang|grc-Latn|aktís}} ({{wikt-lang|grc|ἀκτίς}} 'ray'), referring to the four edges from each vertex to other vertices. Hinton originally spelled the word as ''tessaract''.<ref>
{{cite OED|term=tesseract|ID=199669}}</ref>

== Geometry ==
As a [[regular polytope]] with three [[cube]]s folded together around every edge, it has [[Schläfli symbol]] {4,3,3} with [[Hyperoctahedral group#By dimension|hyperoctahedral symmetry]] of order 384. Constructed as a 4D [[hyperprism]] made of two parallel cubes, it can be named as a composite Schläfli symbol {4,3} × { }, with symmetry order 96. As a 4-4 [[duoprism]], a [[Cartesian product]] of two [[Square (geometry)|squares]], it can be named by a composite Schläfli symbol {4}×{4}, with symmetry order 64. As an [[orthotope]] it can be represented by composite Schläfli symbol { } × { } × { } × { } or { }4, with symmetry order 16.

Since each vertex of a tesseract is adjacent to four edges, the [[vertex figure]] of the tesseract is a regular [[tetrahedron]]. The [[dual polytope]] of the tesseract is the [[16-cell]] with Schläfli symbol {3,3,4}, with which it can be combined to form the compound of tesseract and 16-cell.

Each edge of a regular tesseract is of the same length. This is of interest when using tesseracts as the basis for a [[network topology]] to link multiple processors in [[parallel computing]]: the distance between two nodes is at most 4 and there are many different paths to allow weight balancing.

A tesseract is bounded by eight three-dimensional [[hyperplane]]s. Each pair of non-parallel hyperplanes intersects to form 24 square faces. Three cubes and three squares intersect at each edge. There are four cubes, six squares, and four edges meeting at every vertex. All in all, a tesseract consists of 8 cubes, 24 squares, 32 edges, and 16 vertices.

===Coordinates===

A ''unit tesseract'' has side length {{math|1}}, and is typically taken as the basic unit for [[hypervolume]] in 4-dimensional space. ''The'' unit tesseract in a [[Cartesian coordinate system]] for 4-dimensional space has two opposite vertices at coordinates {{math|[0, 0, 0, 0]}} and {{math|[1, 1, 1, 1]}}, and other vertices with coordinates at all possible combinations of {{math|0}}s and {{math|1}}s. It is the [[Cartesian product]] of the closed [[unit interval]] {{math|[0, 1]}} in each axis.

Sometimes a unit tesseract is centered at the origin, so that its coordinates are the more symmetrical <math>\bigl({\pm\tfrac12}, \pm\tfrac12, \pm\tfrac12, \pm\tfrac12 \bigr).</math> This is the Cartesian product of the closed interval <math>\bigl[{-\tfrac12}, \tfrac12\bigr]</math> in each axis.

Another commonly convenient tesseract is the Cartesian product of the closed interval {{math|[−1, 1]}} in each axis, with vertices at coordinates {{math|(±1, ±1, ±1, ±1)}}. This tesseract has side length 2 and hypervolume {{math|1=24 = 16}}.

===Net===
An unfolding of a [[polytope]] is called a [[Net (polyhedron)|net]]. There are 261 distinct nets of the tesseract.<ref>{{cite web|url=http://unfolding.apperceptual.com/|title=Unfolding an 8-cell|website=Unfolding.apperceptual.com|access-date=21 January 2018}}</ref> The unfoldings of the tesseract can be counted by mapping the nets to ''paired trees'' (a [[Tree (graph theory)|tree]] together with a [[perfect matching]] in its [[Complement graph|complement]]).

Each of the 261 nets can tile 3-space.<ref>[[Matt Parker|Parker, Matt]]. [https://whuts.org/ Which Hypercube Unfoldings Tile Space?] Retrieved 2025 May 11.</ref>

===Construction===
[[File:From Point to Tesseract (Looped Version).gif|thumb|An animation of the shifting in [[dimension]]s]]
The construction of [[hypercube]]s can be imagined the following way:
* '''1-dimensional:''' Two points A and B can be connected to become a line, giving a new line segment AB.
* '''2-dimensional:''' Two parallel line segments AB and CD separated by a distance of AB can be connected to become a square, with the corners marked as ABCD.
* '''3-dimensional:''' Two parallel squares ABCD and EFGH separated by a distance of AB can be connected to become a cube, with the corners marked as ABCDEFGH.
* '''4-dimensional:''' Two parallel cubes ABCDEFGH and IJKLMNOP separated by a distance of AB can be connected to become a tesseract, with the corners marked as ABCDEFGHIJKLMNOP. However, this parallel positioning of two cubes such that their 8 corresponding pairs of vertices are each separated by a distance of AB can only be achieved in a space of 4 or more dimensions.
[[File:Dimension levels.svg|480px|A diagram showing how to create a tesseract from a point]]

The 8 cells of the tesseract may be regarded (three different ways) as two interlocked rings of four cubes.{{Sfn|Coxeter|1970|p=18}}

The tesseract can be decomposed into smaller 4-polytopes. It is the convex hull of the compound of two [[Demihypercube|demitesseracts]] ([[Demitesseract|16-cells]]). It can also be [[Point-set triangulation|triangulated]] into 4-dimensional [[simplex|simplices]] ([[5-cell#Irregular 5-cells|irregular 5-cells]]) that share their vertices with the tesseract. It is known that there are {{val|92487256}} such triangulations<ref>{{citation
| last1 = Pournin | first1 = Lionel
| mr = 3038527
| title = The flip-Graph of the 4-dimensional cube is connected
| journal = [[Discrete & Computational Geometry]]
| pages = 511–530
| volume = 49
| year = 2013
| issue = 3
| doi = 10.1007/s00454-013-9488-y| arxiv = 1201.6543| s2cid = 30946324
}}
</ref> and that the fewest 4-dimensional simplices in any of them is 16.<ref>{{citation
| last1 = Cottle | first1 = Richard W.
| mr = 676709
| title = Minimal triangulation of the 4-cube
| journal = [[Discrete Mathematics (journal)|Discrete Mathematics]]
| pages = 25–29
| volume = 40
| year = 1982
| doi = 10.1016/0012-365X(82)90185-6| doi-access = free
}}</ref>

The dissection of the tesseract into instances of its [[Orthoscheme#Characteristic simplex of the general regular polytope|characteristic simplex]] (a particular [[orthoscheme]] with Coxeter diagram {{CDD|node|4|node|3|node|3|node}}) is the most basic direct construction of the tesseract possible. The '''[[5-cell#Orthoschemes|characteristic 5-cell of the 4-cube]]''' is a [[fundamental region]] of the tesseract's defining [[Coxeter group|symmetry group]], the group which generates the [[B4 polytope|B4 polytopes]]. The tesseract's characteristic simplex directly ''generates'' the tesseract through the actions of the group, by reflecting itself in its own bounding facets (its ''mirror walls'').

=== Radial equilateral symmetry ===
The radius of a [[hypersphere]] circumscribed about a regular polytope is the distance from the polytope's center to one of the vertices, and for the tesseract this radius is equal to its edge length; the diameter of the sphere, the length of the diagonal between opposite vertices of the tesseract, is twice the edge length. Only a few uniform [[polytopes]] have this property, including the four-dimensional tesseract and [[24-cell#Radially equilateral honeycomb|24-cell]], the three-dimensional [[Cuboctahedron#Radial equilateral symmetry|cuboctahedron]], and the two-dimensional [[hexagon]]. In particular, the tesseract is the only hypercube (other than a zero-dimensional point) that is ''radially equilateral''. The longest vertex-to-vertex diagonal of an <math>n</math>-dimensional hypercube of unit edge length is <math>\sqrt{n\vphantom{t}},</math> which for the square is <math>\sqrt2,</math> for the cube is <math>\sqrt3,</math> and only for the tesseract is <math>\sqrt4 = 2</math> edge lengths.

An axis-aligned tesseract inscribed in a unit-radius 3-sphere has vertices with coordinates <math>\bigl({\pm\tfrac12}, \pm\tfrac12, \pm\tfrac12, \pm\tfrac12\bigr).</math>

=== Properties {{anchor|Formulas}} ===
{{tesseract_graph_nonplanar_visual_proof.svg|150px|thumb|right}}
For a tesseract with side length {{Mvar|s}}:

* [[Hypervolume]] (4D): <math>H=s^4</math>
* Surface "volume" (3D): <math>SV=8s^3</math>
*[[Face diagonal]]: <math>d_\mathrm{2}=\sqrt{2} s</math>
*[[Space diagonal|Cell diagonal]]: <math>d_\mathrm{3}=\sqrt{3} s</math>
*4-space diagonal: <math>d_\mathrm{4}=2s</math>

=== As a configuration ===
This [[Regular 4-polytope#As configurations|configuration matrix]] represents the tesseract. The rows and columns correspond to vertices, edges, faces, and cells. The diagonal numbers say how many of each element occur in the whole tesseract. The diagonal reduces to the [[f-vector]] (16,32,24,8).

The nondiagonal numbers say how many of the column's element occur in or at the row's element.{{Sfn|Coxeter|1973|loc=§1.8 Configurations|p=12}} For example, the 2 in the first column of the second row indicates that there are 2 vertices in (i.e., at the extremes of) each edge; the 4 in the second column of the first row indicates that 4 edges meet at each vertex.

The bottom row defines they facets, here cubes, have f-vector (8,12,6). The next row left of diagonal is ridge elements (facet of cube), here a square, (4,4).

The upper row is the f-vector of the [[vertex figure]], here tetrahedra, (4,6,4). The next row is vertex figure ridge, here a triangle, (3,3).

<math>\begin{bmatrix}\begin{matrix}16 & 4 & 6 & 4 \\ 2 & 32 & 3 & 3 \\ 4 & 4 & 24 & 2 \\ 8 & 12 & 6 & 8 \end{matrix}\end{bmatrix}</math>

==Projections==
It is possible to project tesseracts into three- and two-dimensional spaces, similarly to projecting a cube into two-dimensional space.

[[File:Orthogonal projection envelopes tesseract.png|thumb|left|Parallel projection envelopes of the tesseract (each cell is drawn with different color faces, inverted cells are undrawn)]]

[[File:Hypercubeorder binary.svg|thumb|right|The [[rhombic dodecahedron]] forms the convex hull of the tesseract's vertex-first parallel-projection. The number of vertices in the layers of this projection is 1 4 6 4 1—the fourth row in [[Pascal's triangle]].]]

The ''cell-first'' parallel [[graphical projection|projection]] of the tesseract into three-dimensional space has a [[cube|cubical]] envelope. The nearest and farthest cells are projected onto the cube, and the remaining six cells are projected onto the six square faces of the cube.

The ''face-first'' parallel projection of the tesseract into three-dimensional space has a [[cuboid]]al envelope. Two pairs of cells project to the upper and lower halves of this envelope, and the four remaining cells project to the side faces.

The ''edge-first'' parallel projection of the tesseract into three-dimensional space has an envelope in the shape of a [[hexagonal prism]]. Six cells project onto rhombic prisms, which are laid out in the hexagonal prism in a way analogous to how the faces of the 3D cube project onto six rhombs in a hexagonal envelope under vertex-first projection. The two remaining cells project onto the prism bases.

The ''vertex-first'' parallel projection of the tesseract into three-dimensional space has a [[rhombic dodecahedron|rhombic dodecahedral]] envelope. Two vertices of the tesseract are projected to the origin. There are exactly two ways of [[dissection (geometry)|dissecting]] a rhombic dodecahedron into four congruent [[rhombohedron|rhombohedra]], giving a total of eight possible rhombohedra, each a projected [[cube]] of the tesseract. This projection is also the one with maximal volume. One set of projection vectors are {{nowrap|1=''u'' = (1,1,−1,−1)}}, {{nowrap|1=''v'' = (−1,1,−1,1)}}, {{nowrap|1=''w'' = (1,−1,−1,1)}}.

{{clear|left}}
[[File:Orthogonal Tesseract Gif.gif|thumb|right|Animation showing each individual cube within the B4 Coxeter plane projection of the tesseract]]

{| class=wikitable
|+ [[Orthographic projection]]s
|- align=center
![[Coxeter plane]]
!B4
!B4 --> A3
!A3
|- align=center
!Graph
|[[File:4-cube t0.svg|150px]]
|[[File:4-4 duoprism-isotoxal.svg|150px]]
|[[File:4-cube t0 A3.svg|150px]]
|- align=center
![[Dihedral symmetry]]
|[8]
|[4]
|[4]
|- align=center
!Coxeter plane
!Other
!B3 / D4 / A2
!B2 / D3
|- align=center
!Graph
|[[File:4-cube column graph.svg|150px]]
|[[File:4-cube t0 B3.svg|150px]]
|[[File:4-cube t0 B2.svg|150px]]
|- align=center
!Dihedral symmetry
|[2]
|[6]
|[4]
|}

{{-}}
{{multiple image
| class=wikitable
| footer = Orthographic projection Coxeter plane B4 graph with [[hidden lines]] as dash lines, and the tesseract without hidden lines.
| image1 = Tesseract_With_Hidden_Dash_Lines.jpg
| image2 = Tesseract_Without_Hidden_Lines.jpg
| total_width = 300px
}}

{{-}}
{| class="wikitable" width=480
|- align=center valign=top
|rowspan=2|[[File:8-cell.gif]] A 3D projection of a tesseract performing a [[SO(4)#Geometry of 4D rotations|simple rotation]] about a plane in 4-dimensional space. The plane bisects the figure from front-left to back-right and top to bottom.
|[[File:8-cell-orig.gif]] A 3D projection of a tesseract performing a [[SO(4)#Geometry of 4D rotations|double rotation]] about two orthogonal planes in 4-dimensional space.
|}
{{-}}
{| class=wikitable width=640
|- align=center valign=top
|[[File:Animation of three four dimensional cube.webm|thumb|3D Projection of three tesseracts with and without faces]]
|[[File:Tesseract-perspective-vertex-first-PSPclarify.png|200px]] Perspective with '''hidden volume elimination'''. The red corner is the nearest in [[Four-dimensional space|4D]] and has 4 cubical cells meeting around it.
|}

{| class=wikitable width=640
|- align=center valign=top
|[[File:Tesseract tetrahedron shadow matrices.svg|200px|right]]
The [[tetrahedron]] forms the [[convex hull]] of the tesseract's vertex-centered central projection. Four of 8 cubic cells are shown. The 16th vertex is projected to [[point at infinity|infinity]] and the four edges to it are not shown.
|[[File:Stereographic polytope 8cell.png|200px]] [[Stereographic projection]] 
(Edges are projected onto the [[3-sphere]])
|}

{| class=wikitable
|- align=left valign=top
|[[File:3D stereographic projection tesseract.PNG|360px]] [[Stereoscopy|Stereoscopic]] 3D projection of a tesseract (parallel view)
|-
|[[File:Hypercube Disarmed.PNG|360px]] [[Stereoscopy|Stereoscopic]] 3D Disarmed [[Hypercube]]
|}

== Tessellation ==
The tesseract, like all [[hypercubes]], [[Tessellation|tessellates]] [[Euclidean space]]. The self-dual [[tesseractic honeycomb]] consisting of 4 tesseracts around each face has [[Ludwig Schläfli|Schläfli]] symbol '''{4,3,3,4}'''. Hence, the tesseract has a [[dihedral angle]] of 90°.{{Sfn|Coxeter|1973|p=293}}

The tesseract's [[#Radial equilateral symmetry|radial equilateral symmetry]] makes its tessellation the [[Tesseractic honeycomb#Sphere packing|unique regular body-centered cubic lattice]] of equal-sized spheres, in any number of dimensions.

== Related polytopes and honeycombs ==
The tesseract is 4th in a series of [[hypercube]]:
{{Hypercube polytopes}}

The tesseract (8-cell) is the third in the sequence of 6 convex regular 4-polytopes (in order of size and complexity).

{{Regular convex 4-polytopes}}

As a uniform [[duoprism]], the tesseract exists in a [[Uniform 4-polytope#Polygonal prismatic prisms: .5Bp.5D .C3.97 .5B .5D .C3.97 .5B .5D|sequence of uniform duoprisms]]: {''p''}×{4}.

The regular tesseract, along with the [[16-cell]], exists in a set of 15 [[Truncated tesseract#Related uniform polytopes in tesseract symmetry|uniform 4-polytopes with the same symmetry]]. The tesseract {4,3,3} exists in a [[Hexagonal tiling honeycomb#Polytopes and honeycombs with tetrahedral vertex figures|sequence of regular 4-polytopes and honeycombs]], {''p'',3,3} with [[tetrahedron|tetrahedral]] [[vertex figure]]s, {3,3}. The tesseract is also in a [[Order-5 cubic honeycomb#Related polytopes and honeycombs with cubic cells|sequence of regular 4-polytope and honeycombs]], {4,3,''p''} with [[cube|cubic]] [[cell (geometry)|cells]].

{| class=wikitable style="float:right;" width=320
!Orthogonal||Perspective
|-
|[[File:4-generalized-2-cube.svg|160px]]
|[[File:Complex polygon 4-4-2-stereographic3.svg|160px]]
|-
|colspan=2|4{4}2, with 16 vertices and 8 4-edges, with the 8 4-edges shown here as 4 red and 4 blue squares
|}
The [[regular complex polytope]] 4{4}2, {{CDD|4node_1|4|node}}, in <math>\mathbb{C}^2</math> has a real representation as a tesseract or 4-4 [[duoprism]] in 4-dimensional space. 4{4}2 has 16 vertices, and 8 4-edges. Its symmetry is 4[4]2, order 32. It also has a lower symmetry construction, {{CDD|4node_1|2|4node_1}}, or 4{}×4{}, with symmetry 4[2]4, order 16. This is the symmetry if the red and blue 4-edges are considered distinct.<ref>Coxeter, H. S. M., ''Regular Complex Polytopes'', second edition, Cambridge University Press, (1991).</ref>

{{Clear}}

==In popular culture==
Since their discovery, four-dimensional hypercubes have been a popular theme in art, architecture, and science fiction. Notable examples include:

* "[[And He Built a Crooked House]]", [[Robert A. Heinlein|Robert Heinlein]]'s 1940 science fiction story featuring a building in the form of a four-dimensional hypercube.<ref>{{citation
|title=Mathematics in Science Fiction: Mathematics as Science Fiction
|first=David
|last=Fowler
|journal=World Literature Today
|volume=84
|issue=3
|year=2010
|pages=48–52
|doi=10.1353/wlt.2010.0188
|jstor=27871086|s2cid=115769478
}}</ref> This and [[Martin Gardner]]'s "The No-Sided Professor", published in 1946, are among the first in science fiction to introduce readers to the [[Moebius band]], the [[Klein bottle]], and the hypercube (tesseract).
* ''[[Crucifixion (Corpus Hypercubus)]]'', a 1954 oil painting by Salvador Dalí featuring a four-dimensional hypercube unfolded into a three-dimensional [[Latin cross]].<ref>{{citation|title=Dali's dimensions|first=Martin|last=Kemp|journal=[[Nature (journal)|Nature]]|volume=391|issue=27|date=1 January 1998|pages=27|doi=10.1038/34063|bibcode=1998Natur.391...27K|s2cid=5317132|doi-access=free}}</ref>
* The [[Grande Arche]], a monument and building near Paris, France, completed in 1989. According to the monument's engineer, [[Erik Reitzel]], the Grande Arche was designed to resemble the projection of a hypercube.<ref>{{citation|last=Ursyn|first=Anna|title=Knowledge Visualization and Visual Literacy in Science Education|publisher=Information Science Reference|year=2016|isbn=9781522504818|pages=91|contribution-url=https://books.google.com/books?id=-JBJDAAAQBAJ&pg=PA91|contribution=Knowledge Visualization and Visual Literacy in Science Education}}</ref>
* ''[[Fez (video game)|Fez]]'', a video game where one plays a character who can see beyond the two dimensions other characters can see, and must use this ability to solve platforming puzzles. Features "Dot", a tesseract who helps the player navigate the world and tells how to use abilities, fitting the theme of seeing beyond human perception of known dimensional space.<ref>{{cite web|url=http://www.giantbomb.com/dot/3005-23100/|title=Dot (Character) - Giant Bomb|website=Giant Bomb|access-date=21 January 2018}}</ref>
The word ''tesseract'' has been adopted for numerous other uses in popular culture, including as a plot device in works of science fiction, often with little or no connection to the four-dimensional hypercube; see [[Tesseract (disambiguation)]].


==Notes==
{{Reflist}}

== References ==
* {{Cite book | last=Coxeter | first=H.S.M. | author-link=Harold Scott MacDonald Coxeter | year=1973 | title=Regular Polytopes | publisher=Dover | place=New York | edition=3rd | title-link=Regular Polytopes (book) | pages=122–123}}
* F. Arthur Sherk, Peter McMullen, Anthony C. Thompson, Asia Ivic Weiss (1995) ''Kaleidoscopes: Selected Writings of H.S.M. Coxeter'', Wiley-Interscience Publication {{isbn|978-0-471-01003-6}} [http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471010030.html]
** (Paper 22) H.S.M. Coxeter, ''Regular and Semi Regular Polytopes I'', [[Mathematische Zeitschrift]] 46 (1940) 380–407, MR 2,10]
** (Paper 23) H.S.M. Coxeter, ''Regular and Semi-Regular Polytopes II'', [Math. Zeit. 188 (1985) 559-591]
** (Paper 24) H.S.M. Coxeter, ''Regular and Semi-Regular Polytopes III'', [Math. Zeit. 200 (1988) 3-45]
* {{Citation | last=Coxeter | first=H.S.M. | author-link=Harold Scott MacDonald Coxeter | year=1970 | title=Twisted Honeycombs | place=Providence, Rhode Island | journal=Conference Board of the Mathematical Sciences Regional Conference Series in Mathematics | publisher=American Mathematical Society | volume=4 }}
* [[John Horton Conway|John H. Conway]], Heidi Burgiel, Chaim Goodman-Strauss (2008) ''The Symmetries of Things'', {{isbn|978-1-56881-220-5}} (Chapter 26. pp. 409: Hemicubes: 1n1)
* [[Thorold Gosset|T. Gosset]] (1900) ''On the Regular and Semi-Regular Figures in Space of n Dimensions'', [[Messenger of Mathematics]], Macmillan.
* {{cite journal
| last = Hall | first = T. Proctor | authorlink = T. Proctor Hall
| year = 1893
| jstor = 2369565
| title = The projection of fourfold figures on a three-flat
| journal = [[American Journal of Mathematics]]
| volume = 15
| issue = 2 | pages = 179–189
| doi = 10.2307/2369565 }}
* [[Norman Johnson (mathematician)|Norman Johnson]] ''Uniform Polytopes'', Manuscript (1991)
** N.W. Johnson: ''The Theory of Uniform Polytopes and Honeycombs'', Ph.D. (1966)
* [[Victor Schlegel]] (1886) ''Ueber Projectionsmodelle der regelmässigen vier-dimensionalen Körper'', Waren.

== External links ==
* {{KlitzingPolytopes|polychora.htm|4D uniform polytopes (polychora)|x4o3o3o - tes}}
* [http://mrl.nyu.edu/~perlin/demox/Hyper.html ken perlin's home page] A way to visualize hypercubes, by [[Ken Perlin]]
* [https://www.math.union.edu/~dpvc/math/4D/ Some Notes on the Fourth Dimension] includes animated tutorials on several different aspects of the tesseract, by [http://www.math.union.edu/~dpvc/ Davide P. Cervone]
* [http://www.fano.co.uk/hypermodel/tesseract.html Tesseract animation with hidden volume elimination]
{{Hypercube polytopes}}
{{Regular 4-polytopes}}
{{Polytopes}}

[[Category:Algebraic topology]]
[[Category:Regular 4-polytopes]]
[[Category:Cubes]]

File:Tesseract.glb

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OpenDEM 1: Uploaded a work by EmersonCaon from https://sketchfab.com/3d-models/tesseract-b324461a73af4f7ca86c9fcfb445d2b1 with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{br|1=A 3D model of a tesseract is a three-dimensional representation of a hypercube, which is a fourth-dimensional geometric object. It consists of eight vertices, 24 edges, 32 faces, and 16 cells, all of which are cubic in shape. The 3D model allows the user to view the tesseract from different perspectives, manipulate it, and rotate it at any angle to better understand its structure and properties. It can be used for educational, research, or even aesthetic purposes, such as in art and design installations. Some 3D models of tesseracts can also be animated or used in virtual reality environments, allowing users to explore the object in an immersive and interactive environment. In general, the 3D model of a tesseract is a fascinating and intriguing representation of the geometry and mathematics of the fourth dimension.

Translated with DeepL.com (free version)}}
|date=26.03.2023
|source=https://sketchfab.com/3d-models/tesseract-b324461a73af4f7ca86c9fcfb445d2b1
|author=EmersonCaon
|permission=
|other versions=
}}

=={{int:license-header}}==
{{cc-by-4.0}}

Articles Gallery

2025-08-25T16:21:31Z

OpenDEM 1:

'''Explore Wikipedia articles with interactive 3D models for an immersive learning experience.'''

== Medicine and Anatomy ==
Interactive 3D models in medical articles allow students, educators, and professionals to explore complex anatomical structures dynamically. This enhances spatial understanding and improves both teaching and self-directed learning in health sciences.

[[File:Heart.glb|300px|link=Heart]]
[[File:Human_mouth_detailed.glb|300px|link=Human_mouth]]
[[File:Model_of_a_human_brain.glb|300px|link=Human_brain]]

== Incorporating Temporal Dynamics in 3D Animation Visualization ==
Animated 3D models can illustrate how objects or processes change over time, making dynamic developments clearer than static 3D models. By integrating the time axis, they enrich understanding of historical evolution, scientific transformations, or mechanical functions in motion.
[[File:Animated_tectonic_plates_collide_loop.glb|300px|link=Tectonics]]
[[File:Tohoku_earthquake_-_2011.glb|300px|link=Earthquake]]

== Architecture and Cultural Heritage ==
For historical sites and architectural wonders, 3D models bring cultural heritage to life. They allow users to experience the design, construction, and spatial relationships of ancient and iconic structures, supporting preservation and public education.

[[File:Plateau_de_gizeh.glb|300px|link=Giza_Plateau]]
[[File:Heddal_stavkirke.glb|300px|link=Heddal_Stave_Church]]
[[File:The_astronaut_geoglyph_in_nazca_peru.glb|300px|link=Nazca_lines]]

== Astronomy and Space Science ==
3D visualization in astronomical subjects makes vast scales and complex structures accessible. These models can illustrate orbital dynamics, spatial relationships, and the design of space missions to engage both the public and researchers.

[[File:Solar_system.glb|300px|link=Solar_System]]
[[File:International_Space_Station.glb|300px|link=International_Space_Station]]
[[File:Blackhole.glb|300px|link=Black_hole]]

== Engineering and Transportation ==
Interactive 3D models allow enthusiasts, students, and professionals to explore the design and functionality of complex machines. These models illustrate key engineering principles and innovations in transportation.

[[File:Boeing_747.glb|300px|link=Boeing_747]]
[[File:N700-3000_series_shinkansen.glb|300px|Shinkansen]]
[[File:Ford_t.glb|300px|Ford_Model_T]]

== Natural Landscapes and Geography ==
3D models of natural landscapes and geological formations provide an immersive way to appreciate the scale and intricate details of Earth’s features. They support educational initiatives in earth sciences and environmental studies by offering intuitive, visual representations.

[[File:Lees_ferry_grand_canyon_arizona.glb|300px|link=Grand_Canyon]]
[[File:Mount_everest_and_mountains_tibet_nepal.glb|300px|link=Mount_Everest]]
[[File:Monument_valley_-_merrick_butte.glb|300px|link=Merrick_Butte]]

== Biology ==
3D models provide a realistic representation of objects, which helps improve understanding of their shape, function, and spatial relationships. This is especially useful for studying organisms, fossils, and anatomical features, where a detailed and accurate visualization can bring insights into its biology and evolution.

[[File:Triceratops.glb|300px|link=Triceratops]]
[[File:Red_Fox_Cranium.glb|300px|link=Red_fox]]
[[File:Bacteriophage.glb|300px|link=Bacteriophage]]

== Mathematics ==
3D models enable precise visualization and analysis of surface geometry, capturing curvature, texture, and topology beyond the limits of 2D representation. Some surfaces, such as the Steiner surface, are hard to visualise without a 3D model.

[[File:Klein_bottle.glb|300px|link=Klein_bottle]]
[[File:Mobius_strips.glb|300px|link=Möbius_strip]]
[[File:Roman.glb|300px|link=Roman_surface]]

Tectonics

2025-08-25T16:20:42Z

OpenDEM 1:

{{Short description|Process of evolution of Earth's crust}}
{{For|an architectural term|Tectonics (architecture)}}
{{Redirect|Tectonic}}
{{Use dmy dates|date=July 2022}}
[[File:Animated_tectonic_plates_collide_loop.glb|thumb|Animated Tectonic Plates Collide]]
{{Geophysics|all}}

[[File:Plate tectonics map.gif|thumb|upright=1.8]]

'''Tectonics''' ({{etymology|grc|''{{wikt-lang|grc|τεκτονικός}}'' {{grc-transl|τεκτονικός}}|pertaining to [[construction|building]]}} via [[Latin]] {{wikt-lang|la|tectonicus}})<ref>{{OEtymD|tectonic}}</ref> are the processes that result in the structure and properties of [[Earth's crust]] and its evolution through time. The field of ''planetary tectonics'' extends the concept to other planets and moons.<ref>
Geologists (as distinct from architects) may define ''tectonics'' as "the architecture of the Earth's crust" -
{{cite book
|last1 = O'Hara
|first1 = Kieran D.
|date = 19 April 2018
|title = A Brief History of Geology
|url = https://books.google.com/books?id=O7pQDwAAQBAJ
|location = Cambridge
|publisher = Cambridge University Press
|isbn = 9781107176188
|access-date = 23 March 2023
|quote = The words tectonics and architecture are derived from the same Greek root, and tectonics is defined as the architecture of the Earth's crust.
}}
</ref><ref name=Watters_etal_2010>
{{cite book
|last1 = Watters
|first1 = Thomas R.
|last2 = Schultz
|first2 = Richard A.
|editor-last1 = Watters
|editor-first1 = Thomas R.
|editor-last2 = Schultz
|editor-first2 = Richard A.
|year = 2010
|chapter = Planetary tectonics: introduction
|title = Planetary Tectonics
|url = https://books.google.com/books?id=9PD5hxPb6fkC
|series = Cambridge Planetary Science, ISSN 0265-3044 – Volume 11
|location = Cambridge
|publisher = Cambridge University Press
|isbn = 9780521765732
|access-date = 23 March 2023
|page = 2
|quote = Since the 1960s, an armada of exploratory spacecraft have identified widespread evidence of tectonism on all the terrestrial planets, most of the satellites of the outer planets, and on a number of asteroids. Tectonic landforms on large and small bodies in the solar system are as ubiquitous as impact craters.
}}
</ref>

These processes include those of [[orogeny|mountain-building]], the growth and behavior of the strong, old cores of continents known as [[craton]]s, and the ways in which the relatively rigid [[tectonic plate|plates]] that constitute Earth's outer shell interact with each other. Principles of tectonics also provide a framework for understanding the [[earthquake]] and [[volcanic belt]]s that directly affect much of the global population.

Tectonic studies are important as guides for [[economic geology|economic geologists]] searching for [[fossil fuel]]s and [[ore deposit]]s of metallic and nonmetallic resources. An understanding of tectonic principles can help [[geomorphology|geomorphologists]] to explain [[Erosion and tectonics|erosion patterns]] and other Earth-surface features.<ref>
{{cite book
|last1 = Anderson
|first1 = Robert S.
|author-link1 = Robert S. Anderson
|last2 = Burbank
|first2 = Douglas W.
|date = 2 November 2011
|orig-date = 2001
|chapter = Rates of erosion and uplift
|title = Tectonic Geomorphology
|url = https://books.google.com/books?id=83FuAvtSwE4C
|edition = 2
|location = Chichester, West Sussex
|publisher = John Wiley & Sons
|isbn = 9781444345049
|access-date = 23 March 2023
}}
</ref>

{{TOC right}}

==Main types of tectonic regime==
===Extensional tectonics===
{{Main article|Extensional tectonics}}

Extensional tectonics is associated with the stretching and thinning of the crust or the [[lithosphere]]. This type of tectonics is found at divergent plate boundaries, in continental [[rift]]s, during and after a period of [[continental collision]] caused by the lateral spreading of the thickened crust formed, at releasing bends in [[Fault (geology)#Strike-slip faults|strike-slip faults]], in [[back-arc basin]]s, and on the continental end of [[passive margin]] sequences where a [[Décollement|detachment layer]] is present.<ref>{{citation|url=http://bmeyer2.free.fr/pdf/2002-TerraNova.pdf|last1=Armijo|first1=R.|last2=Meyer|first2=B.|last3=Navarro|first3=S.|last4=King|first4=G.|last5=Barka|first5=A.|author-link5=Aykut Barka|year=2002|title=Asymmetric slip partitioning in the Sea of Marmara pull-apart: a clue to propagation processes of the North Anatolian Fault?|journal=Terra Nova|publisher=[[Wiley-Blackwell]]|volume=14|issue=2|pages=80–86|doi=10.1046/j.1365-3121.2002.00397.x|bibcode=2002TeNov..14...80A|citeseerx=10.1.1.546.4111|s2cid=49553634 }}</ref><ref name="Sdrolias_&_Muller_2006">{{Cite journal|last1=Sdrolias|first1=M|last2=Muller|first2=R.D.|date=2006|title=Controls on back-arc basin formations|journal=Geochemistry, Geophysics, Geosystems|volume=7|issue=4|pages=Q04016|bibcode=2006GGG.....7.4016S|doi=10.1029/2005GC001090|doi-access=free|s2cid=129068818}}</ref><ref name="Brun_&_Fort_2011">{{Cite journal |last1=Brun |first1=J,-P. |last2=Fort |first2=X. |title=Salt tectonics at passive margins: Geology versus models |journal=Marine and Petroleum Geology |date=2011 |volume=28 |issue=6 |pages=1123–1145 |doi=10.1016/j.marpetgeo.2011.03.004|bibcode=2011MarPG..28.1123B }}</ref>

===Thrust (contractional) tectonics===
{{Main article|Thrust tectonics}}

Thrust tectonics is associated with the shortening and thickening of the crust, or the lithosphere. This type of tectonics is found at zones of [[continental collision]], at restraining bends in strike-slip faults, and at the oceanward part of passive margin sequences where a detachment layer is present.<ref name="Butler_&_Bond_2020">{{Cite book |last=Butler |first=R. |title=Principles of Geologic Analysis |last2=Bond |first2=C. |publisher=Elsevier |year=2020 |isbn=9780444641359 |editor-last=Scarselli |editor-first=N. |edition=2 |series=Regional Geology and Tectonics |volume=1 |pages=149–167 |chapter=Chapter 9 – Thrust systems and contractional tectonics |doi=10.1016/B978-0-444-64134-2.00008-0 |editor-last2=Adam |editor-first2=J. |editor-last3=Chiarella |editor-first3=D.}}</ref>

===Strike-slip tectonics===
{{Main article|Strike-slip tectonics}}

[[File:Aerial-SanAndreas-CarrizoPlain.jpg|thumb|[[San Andreas Fault|San Andreas transform fault]] on the [[Carrizo Plain]]]]

Strike-slip tectonics is associated with the relative lateral movement of parts of the crust or the lithosphere. This type of tectonics is found along oceanic and continental [[transform fault]]s which connect offset segments of [[mid-ocean ridge]]s. Strike-slip tectonics also occurs at lateral offsets in extensional and [[thrust fault]] systems. In areas involved with [[Continental collision|plate collisions]] strike-slip deformation occurs in the over-riding plate in zones of oblique collision and accommodates deformation in the [[Foreland basin|foreland]] to a collisional belt.<ref name="Burg_2017">{{Cite web |last=Burg |first=J.-P. |date=2017 |title=Strike-slip and Oblique-slip tectonics |url=https://www.files.ethz.ch/structuralgeology/jpb/files/english/5wrench.pdf |access-date=26 September 2022}}</ref>

==Plate tectonics==
{{Main article|Plate tectonics}}

[[File:JPVD-NGTM2023-Network.jpg|upright=2|right|thumb|The Tectonic Network of Earth. Legend: Brown: Terrane (microplate) boundaries in the continents and Mobile Belts, Cyan: Terranes of the Oceanic Plates, Blue: Oceanic transform faults; Red and orange: Fault zones in the Continental and Mountain belt domain; Purple: Main subduction zones and suture zones; Green: Continental margins]]

In plate tectonics, the outermost part of Earth known as the [[lithosphere]] (the [[Crust (geology)|crust]] and uppermost [[Mantle (geology)|mantle]]) act as a single mechanical layer. The lithosphere is divided into separate "plates" that move relative to each other on the underlying, relatively weak [[asthenosphere]] in a process ultimately driven by the continuous loss of heat from Earth's interior. There are three main types of plate boundaries: [[Divergent boundary|divergent]], where plates move apart from each other and new lithosphere is formed in the process of [[sea-floor spreading]]; [[Transform fault|transform]], where plates slide past each other, and [[convergent boundary|convergent]], where plates converge and lithosphere is "consumed" by the process of [[subduction]]. Convergent and transform boundaries are responsible for most of the world's major ([[Moment magnitude scale|Mw]] > 7) [[earthquake]]s. Convergent and divergent boundaries are also the site of most of the world's [[volcano]]es, such as around the Pacific [[Ring of Fire]]. Most of the deformation in the lithosphere is related to the interaction between plates at or near plate boundaries.
The latest studies, based on the integration of available geological data, and satellite imagery and Gravimetric and magnetic anomaly datasets have shown that the crust of Earth is dissected by thousands of different types of tectonic elements which define the subdivision into numerous smaller microplates which have amalgamated into the larger Plates.<ref name ='van Dijk_2023'>van Dijk, J.P. (2023); The New Global Tectonic Map – Analyses and Implications. Terra Nova, 2023, 27 pp. {{doi|10.1111/TER.12662}}</ref>

==Other fields of tectonic studies==
===Salt tectonics===
{{Main article|Salt tectonics}}

Salt tectonics is concerned with the structural geometries and deformation processes associated with the presence of significant thicknesses of [[rock salt]] within a sequence of rocks. This is due both to the low density of salt, which does not increase with burial, and its low strength.<ref name="Hudec_&_Jackson_2007">{{Cite journal |last=Hudec |first=M.R. |last2=Jackson |first2=M.P.A. |date=2007 |title=Terra infirma: Understanding salt tectonics |journal=Earth-Science Reviews |volume=82 |issue=1–2 |pages=1–28 |doi=10.1016/j.earscirev.2007.01.001}}</ref>

===Neotectonics===
{{Main article|Neotectonics}}

Neotectonics is the study of the motions and deformations of [[Earth's crust]] ([[geology|geological]] and [[geomorphology|geomorphological]] processes) that are current or recent in [[Geologic time scale|geological time]]. The term may also refer to the motions and deformations themselves. The corresponding time frame is referred to as the ''neotectonic period''. Accordingly, the preceding time is referred to as ''palaeotectonic period''.<ref>"Encyclopedia of Coastal Science" (2005), Springer, {{ISBN|978-1-4020-1903-6}}, Chapter 1: "Tectonics and Neotectonics" {{doi|10.1007/1-4020-3880-1}}
</ref>

===Tectonophysics===
{{Main article|Tectonophysics}}

Tectonophysics is the study of the physical processes associated with deformation of the crust and mantle from the scale of individual mineral grains up to that of tectonic plates.<ref>{{Citation |last=Foulger |first=Gillian R. |title=The Plate Theory for Volcanism |date=2021 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780081029084001053 |work=Encyclopedia of Geology |pages=879–890 |access-date=2023-10-23 |publisher=Elsevier |language=en |doi=10.1016/b978-0-08-102908-4.00105-3 |isbn=978-0-08-102909-1|url-access=subscription }}</ref>

===Seismotectonics===
{{Main article|Seismotectonics}}

Seismotectonics is the study of the relationship between earthquakes, active tectonics, and individual [[Fault (geology)|faults]] in a region. It seeks to understand which faults are responsible for seismic activity in an area by analysing a combination of regional tectonics, recent instrumentally recorded events, accounts of historical earthquakes, and geomorphological evidence. This information can then be used to quantify the [[seismic hazard]] of an area.<ref name="Slejko_2012">{{Cite book |title=Recent Evolution and Seismicity of the Mediterranean Region |date=2012 |publisher=Springer |isbn=9789401120166 |editor-last=E. Boschi |editor-first=E. |chapter=A review of the Eastern Alps – Northern Dinarides Seismotectonics |editor-last2=Mantovani |editor-first2=E. |editor-last3=Morelli |editor-first3=A. |chapter-url=https://books.google.com/books?id=gbbvCAAAQBAJ&dq=seismotectonics+definition&pg=PA251}}</ref>

===Impact tectonics===
Impact tectonics is the study of modification of the lithosphere through high velocity impact cratering events.<ref>{{cite book | veditors=Koeberl C, Henkel H | date= 2005 | title=Impact Tectonics | series= Impact Studies | publisher=Springer Berlin Heidelberg | url=http://dx.doi.org/10.1007/3-540-27548-7 | doi=10.1007/3-540-27548-7| isbn= 978-3-540-24181-2 }}</ref>

===Planetary tectonics===
Techniques used in the analysis of tectonics on Earth have also been applied to the study of the [[Planetary science|planets]] and their moons, especially [[tectonics on icy moons|icy moons]].<ref name=Watters_etal_2010/>

==See also==
{{Portal|Geology}}
* [[Glarus thrust]] ([[UNESCO]] World Heritage Site]])
* [[Mohorovičić discontinuity]]
* [[Seismology]]
* [[Tectonophysics]]
* [[Volcanology]]

==References==
{{reflist}}

==Further reading==
* Edward A. Keller (2001) [https://books.google.com/books?id=sXASAQAAIAAJ ''Active Tectonics: Earthquakes, Uplift, and Landscape''] Prentice Hall; 2nd edition, {{ISBN|0-13-088230-5}}
* Stanley A. Schumm, Jean F. Dumont and John M. Holbrook (2002) ''Active Tectonics and Alluvial Rivers'', Cambridge University Press; Reprint edition, {{ISBN|0-521-89058-6}}
* {{cite book|author=B.A. van der Pluijm and S. Marshak|title=Earth Structure – An Introduction to Structural Geology and Tectonics. 2nd edition|url=http://globalchange.umich.edu/ben/ES/earthstructure.htm|publisher=W.W. Norton|location=New York|year=2004|page=656|isbn=0-393-92467-X|access-date=31 October 2008|archive-date=3 May 2017|archive-url=https://web.archive.org/web/20170503085143/http://www.globalchange.umich.edu/Ben/ES/earthstructure.htm|url-status=dead}}

==External links==
{{wiktionary|tectonics|tectonic}}
* [http://www.tectonic-forces.org/ The Origin and the Mechanics of the Forces Responsible for Tectonic Plate Movements]
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[[Category:Tectonics| ]]

Earthquake

2025-08-25T16:20:03Z

OpenDEM 1:

{{Short description|Sudden movement of the Earth's crust}}
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{{Use American English|date=August 2021}}
[[File:Tohoku_earthquake_-_2011.glb|thumb|The Tōhoku earthquake (9.1 magnitude) hit Japan on March 11, 2011 ]]
[[File:Quake epicenters 1963-98.png|thumb|upright=1.35|Earthquake [[epicenter]]s occur mostly along [[Plate tectonics|tectonic plate]] boundaries, especially on the Pacific [[Ring of Fire]].]]
{{Earthquakes}}

An '''earthquake''', also called a '''quake''', '''tremor''', or '''temblor''', is the shaking of the [[Earth]]'s surface resulting from a sudden release of energy in the [[lithosphere]] that creates [[seismic wave]]s. Earthquakes can range in [[Seismic intensity scales|intensity]], from those so weak they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The [[seismicity]] at a particular location in the Earth is the average rate of seismic energy release per unit volume.

In its most general sense, the word ''earthquake'' is used to describe any seismic event that generates seismic waves. Earthquakes can occur naturally or be induced by human activities, such as [[mining]], [[fracking]], and [[nuclear weapons testing]]. The initial point of rupture is called the [[hypocenter]] or focus, while the ground level directly above it is the [[epicenter]]. Earthquakes are primarily caused by geological [[Fault (geology)|faults]], but also by [[volcanism]], landslides, and other seismic events.

Significant historical earthquakes include the [[1556 Shaanxi earthquake]] in China, with over 830,000 fatalities, and the [[1960 Valdivia earthquake]] in Chile, the largest ever recorded at 9.5 [[Seismic magnitude scales|magnitude]]. Earthquakes result in various effects, such as ground shaking and [[soil liquefaction]], leading to significant damage and loss of life. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a [[tsunami]]. Earthquakes can trigger [[landslide]]s. Earthquakes' occurrence is influenced by [[tectonic]] movements along faults, including normal, reverse (thrust), and strike-slip faults, with energy release and rupture dynamics governed by the [[elastic-rebound theory]].

Efforts to manage earthquake risks involve prediction, forecasting, and preparedness, including [[seismic retrofit]]ting and [[earthquake engineering]] to design structures that withstand shaking. The cultural impact of earthquakes spans myths, religious beliefs, and modern media, reflecting their profound influence on human societies. Similar seismic phenomena, known as [[marsquake]]s and [[moonquakes]], have been observed on other celestial bodies, indicating the universality of such events beyond Earth.

== Terminology ==
An earthquake is the shaking of the surface of [[Earth]] resulting from a sudden release of energy in the [[lithosphere]] that creates [[seismic wave]]s. Earthquakes may also be referred to as ''quakes'', ''tremors'', or ''temblors''. The word ''tremor'' is also used for [[Episodic tremor and slip|non-earthquake seismic rumbling]].

In its most general sense, an ''earthquake'' is any seismic event—whether natural or caused by humans—that generates seismic waves. Earthquakes are caused mostly by the rupture of geological [[Fault (geology)|faults]] but also by other events such as volcanic activity, landslides, mine blasts, [[fracking]] and [[Underground nuclear testing|nuclear tests]]. An earthquake's point of initial rupture is called its [[hypocenter]] or focus. The [[epicenter]] is the point at ground level directly above the hypocenter.

The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The [[seismicity]] at a particular location in the Earth is the average rate of seismic energy release per unit volume.

==Major examples==
{{Main|Lists of earthquakes}}

[[File:Map of earthquakes 1900-.svg|thumb|upright=1.8|Earthquakes (M6.0+) since 1900 through 2017]]
[[File:USGS magnitude 8 earthquakes since 1900.svg|thumb|upright=1.8|Earthquakes of magnitude 8.0 and greater from 1900 to 2018. The apparent 3D volumes of the bubbles are linearly proportional to their respective fatalities.<ref>{{Cite web|url=https://earthquake.usgs.gov/earthquakes/eqarchives/year/mag8/magnitude8_1900_date.php|archiveurl=https://web.archive.org/web/20160414014457/http://earthquake.usgs.gov/earthquakes/eqarchives/year/mag8/magnitude8_1900_date.php|url-status=dead|title=USGS: Magnitude 8 and Greater Earthquakes Since 1900|archivedate=April 14, 2016}}</ref>]]

One of the most devastating earthquakes in recorded history was the [[1556 Shaanxi earthquake]], which occurred on 23 January 1556 in [[Shaanxi]], China. More than 100,000 people died, with the region losing up to 830,000 people afterwards due to emmigration, plague, and famine.<ref>{{cite web |url=https://earthquake.usgs.gov/earthquakes/world/most_destructive.php |title=Earthquakes with 50,000 or More Deaths |archive-url=https://web.archive.org/web/20091101175733/http://earthquake.usgs.gov/earthquakes/world/most_destructive.php |archive-date=November 1, 2009 |url-status=dead |publisher=United States Geological Survey}}</ref> Most houses in the area were [[yaodong]]s—dwellings carved out of [[loess]] hillsides—and many victims were killed when these structures collapsed. The [[1976 Tangshan earthquake]], which killed between 240,000 and 655,000 people, was the deadliest of the 20th century.<ref>Spignesi, Stephen J. (2005). ''Catastrophe!: The 100 Greatest Disasters of All Time''. {{ISBN|0-8065-2558-4}}</ref>

The [[1960 Valdivia earthquake|1960 Chilean earthquake]] is the largest earthquake that has been measured on a seismograph, reaching 9.5 magnitude on 22 May 1960.<ref name="usgsfacts"/><ref name="wp100414"/> Its epicenter was near Cañete, Chile. The energy released was approximately twice that of the next most powerful earthquake, the [[Good Friday earthquake]] (27 March 1964), which was centered in [[Prince William Sound]], Alaska.<ref>{{cite web|url=http://www.gps.caltech.edu/uploads/File/People/kanamori/HKjgr77.pdf |title=The Energy Release in Great Earthquakes |author=Kanamori Hiroo |publisher=Journal of Geophysical Research |access-date=2010-10-10 |url-status=dead |archive-url=https://web.archive.org/web/20100723182215/http://www.gps.caltech.edu/uploads/File/People/kanamori/HKjgr77.pdf |archive-date=2010-07-23 }}</ref><ref>{{cite web |url=https://earthquake.usgs.gov/learn/topics/how_much_bigger.php |title=How Much Bigger? |publisher=United States Geological Survey |access-date=2010-10-10 |archive-date=2011-06-07 |archive-url=https://web.archive.org/web/20110607144219/http://earthquake.usgs.gov/learn/topics/how_much_bigger.php |url-status=live }}</ref> The ten largest recorded earthquakes have all been [[megathrust earthquake]]s; however, of these ten, only the [[2004 Indian Ocean earthquake]] is simultaneously one of the deadliest earthquakes in history.

Earthquakes that caused the greatest loss of life, while powerful, were deadly because of their proximity to either heavily populated areas or the ocean, where earthquakes often create [[tsunamis]] that can devastate communities thousands of kilometers away. Regions most at risk for great loss of life include those where earthquakes are relatively rare but powerful, and poor regions with lax, unenforced, or nonexistent seismic building codes.

==Occurrence==
[[File:Fault types.svg|thumb|Three types of faults: 
A. [[strike-slip fault|Strike-slip]] 
B. [[Normal fault|Normal]] 
C. [[Reverse fault|Reverse]]
]]

[[Tectonics|Tectonic]] earthquakes occur anywhere on the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a [[Fault (geology)|fault plane]]. The sides of a fault move past each other smoothly and [[Aseismic creep|aseismically]] only if there are no irregularities or [[Asperity (faults)|asperities]] along the fault surface that increases the frictional resistance. Most fault surfaces do have such asperities, which leads to a form of [[Stick-slip phenomenon|stick-slip behavior]]. Once the fault has locked, continued relative motion between the plates leads to increasing stress and, therefore, stored strain energy in the volume around the fault surface. This continues until the stress has risen sufficiently to break through the asperity, suddenly allowing sliding over the locked portion of the fault, releasing the [[Potential energy|stored energy]].<ref name="Ohnaka">{{cite book | url=https://books.google.com/books?id=Bp0gAwAAQBAJ&pg=PA234 | title=The Physics of Rock Failure and Earthquakes | publisher=Cambridge University Press | author=Ohnaka, M. | year=2013 | page=148 | isbn=978-1-107-35533-0}}</ref> This energy is released as a combination of radiated elastic [[Strain (materials science)|strain]] [[seismic waves]],<ref>{{cite journal | last1 = Vassiliou | first1 = Marius | last2 = Kanamori | first2 = Hiroo | year = 1982 | title = The Energy Release in Earthquakes | journal = Bull. Seismol. Soc. Am. | volume = 72 | pages = 371–387 }}</ref> frictional heating of the fault surface, and cracking of the rock, thus causing an earthquake.

This process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure is referred to as the [[elastic-rebound theory]]. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as seismic energy. Most of the earthquake's energy is used to power the earthquake [[Fracture (geology)|fracture]] growth or is converted into heat generated by friction. Therefore, earthquakes lower the Earth's available [[elastic potential energy]] and raise its temperature, though these changes are negligible compared to the conductive and convective flow of heat out from the [[Structure of the Earth|Earth's deep interior.]]<ref name="USGS1">{{cite web|last=Spence |first=William |author2=S.A. Sipkin |author3=G.L. Choy |title=Measuring the Size of an Earthquake |publisher=United States Geological Survey|year=1989 |url=https://earthquake.usgs.gov/learning/topics/measure.php |access-date=2006-11-03 |url-status=dead |archive-url=https://web.archive.org/web/20090901233601/http://earthquake.usgs.gov/learning/topics/measure.php |archive-date=2009-09-01 }}</ref>

===Fault types===
{{Further|Fault (geology)|Strike and dip}}
There are three main types of fault, all of which may cause an [[interplate earthquake]]: normal, reverse (thrust), and strike-slip. Normal and reverse faulting are examples of dip-slip, where the displacement along the fault is in the direction of dip and where movement on them involves a vertical component. Many earthquakes are caused by movement on faults that have components of both dip-slip and strike-slip; this is known as oblique slip.

The topmost, brittle part of the Earth's crust, and the cool slabs of the tectonic plates that are descending into the hot mantle, are the only parts of our planet that can store elastic energy and release it in fault ruptures. Rocks hotter than about {{cvt|300|C||}} flow in response to stress; they do not rupture in earthquakes.<ref>{{cite journal |last1=Sibson |first1=R.H. |year=1982 |title=Fault Zone Models, Heat Flow, and the Depth Distribution of Earthquakes in the Continental Crust of the United States |journal=Bulletin of the Seismological Society of America |volume=72 |issue=1 |pages=151–163}}</ref><ref>Sibson, R.H. (2002) "Geology of the crustal earthquake source" International handbook of earthquake and engineering seismology, Volume 1, Part 1, p. 455, eds. W H K Lee, H Kanamori, P C Jennings, and C. Kisslinger, Academic Press, {{ISBN|978-0-12-440652-0}}</ref> The maximum observed lengths of ruptures and mapped faults (which may break in a single rupture) are approximately {{cvt|1000|km|||}}. Examples are the earthquakes in [[1957 Andreanof Islands earthquake|Alaska (1957)]], [[1960 Valdivia earthquake|Chile (1960)]], and [[2004 Indian Ocean earthquake and tsunami|Sumatra (2004)]], all in subduction zones. The longest earthquake ruptures on strike-slip faults, like the [[San Andreas Fault]] ([[1857 Fort Tejon earthquake|1857]], [[1906 San Francisco earthquake|1906]]), the [[North Anatolian Fault]] in Turkey ([[1939 Erzincan earthquake|1939]]), and the [[Denali Fault]] in Alaska ([[2002 Denali earthquake|2002]]), are about half to one third as long as the lengths along subducting plate margins, and those along normal faults are even shorter.

==== Normal faults ====
Normal faults occur mainly in areas where the crust is being [[Extensional tectonics|extended]] such as a [[divergent boundary]]. Earthquakes associated with normal faults are generally less than magnitude 7. Maximum magnitudes along many normal faults are even more limited because many of them are located along spreading centers, as in Iceland, where the thickness of the brittle layer is only about {{convert|6|km|spell=in||}}.<ref>Hjaltadóttir S., 2010, "Use of relatively located microearthquakes to map fault patterns and estimate the thickness of the brittle crust in Southwest Iceland"</ref><ref>{{cite web |title=Reports and publications | Seismicity | Icelandic Meteorological office |url=http://en.vedur.is/earthquakes-and-volcanism/reports-and-publications/ |access-date=2011-07-24 |publisher=En.vedur.is |archive-date=2008-04-14 |archive-url=https://web.archive.org/web/20080414235419/http://en.vedur.is/earthquakes-and-volcanism/reports-and-publications/ |url-status=live }}</ref>

==== Reverse faults ====
Reverse faults occur in areas where the crust is being [[Thrust tectonics|shortened]] such as at a [[convergent boundary]]. Reverse faults, particularly those along convergent boundaries, are associated with the most powerful earthquakes (called [[megathrust earthquake]]s) including almost all of those of magnitude 8 or more. Megathrust earthquakes are responsible for about 90% of the total seismic moment released worldwide.<ref>{{citation |last1=Stern |first1=Robert J. |title=Subduction zones |journal=Reviews of Geophysics |volume=40 |issue=4 |page=17 |year=2002 |bibcode=2002RvGeo..40.1012S |doi=10.1029/2001RG000108 |s2cid=247695067|doi-access=free }}</ref>

==== Strike-slip faults ====
[[Strike-slip fault]]s are steep structures where the two sides of the fault slip horizontally past each other; transform boundaries are a particular type of strike-slip fault. Strike-slip faults, particularly continental [[Transform fault|transforms]], can produce major earthquakes up to about magnitude 8. Strike-slip faults tend to be oriented near vertically, resulting in an approximate width of {{cvt|10|km|||}} within the brittle crust.<ref>{{cite web |title=Instrumental California Earthquake Catalog |url=http://wgcep.org/data-inst_eq_cat |url-status=dead |archive-url=https://web.archive.org/web/20110725021215/http://wgcep.org/data-inst_eq_cat |archive-date=2011-07-25 |access-date=2011-07-24 |publisher=WGCEP}}</ref> Thus, earthquakes with magnitudes much larger than 8 are not possible.

[[File:Kluft-photo-Carrizo-Plain-Nov-2007-Img 0327.jpg|thumb|left|Aerial photo of the San Andreas Fault in the [[Carrizo Plain]], northwest of Los Angeles]]

In addition, there exists a hierarchy of stress levels in the three fault types. Thrust faults are generated by the highest, strike-slip by intermediate, and normal faults by the lowest stress levels.<ref>{{cite journal | last1 = Schorlemmer | first1 = D. | last2 = Wiemer | first2 = S. | last3 = Wyss | first3 = M. | year = 2005 | title = Variations in earthquake-size distribution across different stress regimes | journal = Nature | volume = 437 | issue = 7058| pages = 539–542 |bibcode = 2005Natur.437..539S |doi = 10.1038/nature04094 | pmid = 16177788 | s2cid = 4327471 }}</ref> This can easily be understood by considering the direction of the greatest principal stress, the direction of the force that "pushes" the rock mass during the faulting. In the case of normal faults, the rock mass is pushed down in a vertical direction, thus the pushing force (''greatest'' principal stress) equals the weight of the rock mass itself. In the case of thrusting, the rock mass "escapes" in the direction of the least principal stress, namely upward, lifting the rock mass, and thus, the overburden equals the ''least'' principal stress. Strike-slip faulting is intermediate between the other two types described above. This difference in stress regime in the three faulting environments can contribute to differences in stress drop during faulting, which contributes to differences in the radiated energy, regardless of fault dimensions.

=== Energy released ===
For every unit increase in seismic magnitude, there is a roughly thirty-fold increase in the energy released. For instance, an earthquake of magnitude 6.0 releases approximately 32 times as much energy as an earthquake of magnitude 5.0, and a 7.0 magnitude earthquake releases about 1,000 times as much energy as a 5.0 magnitude earthquake. An 8.6-magnitude earthquake releases the same amount of energy as 10,000 atomic bombs of the size used in [[World War II]].<ref>Geoscience Australia.{{full citation needed|date=December 2022}}</ref>

This is so because the energy released in an earthquake, and thus its magnitude, is proportional to the area of the fault that ruptures<ref>{{cite journal |last1=Wyss |first1=M. |year=1979 |title=Estimating expectable maximum magnitude of earthquakes from fault dimensions |journal=Geology |volume=7 |issue=7| pages=336–340 |bibcode=1979Geo.....7..336W |doi=10.1130/0091-7613(1979)7<336:EMEMOE>2.0.CO;2}}</ref> and the stress drop. Therefore, the greater the length and width of the faulted area, the greater the resulting magnitude. The most important parameter controlling the maximum earthquake magnitude on a fault, however, is not the maximum available length, but the available width because the latter varies by a factor of 20. Along converging plate margins, the dip angle of the rupture plane is very shallow, typically about 10 degrees.<ref>{{cite web |url=http://www.globalcmt.org/CMTsearch.html |title=Global Centroid Moment Tensor Catalog |publisher=Globalcmt.org |access-date=2011-07-24 |archive-date=2011-07-19 |archive-url=https://web.archive.org/web/20110719183137/http://www.globalcmt.org/CMTsearch.html |url-status=live }}</ref> Thus, the width of the plane within the top brittle crust of the Earth can reach {{cvt|50–100|km|||}} (such as in [[2011 Tōhoku earthquake and tsunami|Japan, 2011]], or in [[1964 Alaska earthquake|Alaska, 1964]]), making the most powerful earthquakes possible.

===Focus===
{{Main|Depth of focus (tectonics)}}
[[File:HotelSanSalvador.jpg|thumb|Collapsed Gran Hotel building in the [[San Salvador]] metropolis, after the shallow [[1986 San Salvador earthquake]]]]

The majority of tectonic earthquakes originate in the Ring of Fire at depths not exceeding tens of kilometers. Earthquakes occurring at depths less than {{cvt|70|km|||}} are classified as "shallow-focus" earthquakes, while those with focal depths between {{cvt|70|and|300|km|}} are commonly termed "mid-focus" or "intermediate-depth" earthquakes.

In [[subduction]] zones, where older and colder [[oceanic crust]] descends beneath another tectonic plate, [[deep-focus earthquake]]s may occur at much greater depths (ranging from {{cvt|300|to|700|km|}}).<ref>{{cite web| publisher = [[National Earthquake Information Center]]| title = M7.5 Northern Peru Earthquake of 26 September 2005| date = 17 October 2005| url = ftp://hazards.cr.usgs.gov/maps/sigeqs/20050926/20050926.pdf| archive-url = https://web.archive.org/web/20170525100314/ftp://hazards.cr.usgs.gov/maps/sigeqs/20050926/20050926.pdf| archive-date = 2017-05-25| url-status = dead| access-date = 2008-08-01}}</ref> These seismically active areas of subduction are known as [[Wadati–Benioff zone]]s. Deep-focus earthquakes occur at depths where the subducted [[lithosphere]] should no longer be brittle, due to the high temperature and pressure. A possible mechanism for the generation of deep-focus earthquakes is faulting caused by [[olivine]] undergoing a [[phase transition]] into a [[spinel]] structure.<ref name="olivine">{{cite journal| last1 = Greene II | first1 = H.W.| last2 = Burnley | first2 = P.C.| title = A new self-organizing mechanism for deep-focus earthquakes| journal = Nature| volume = 341| issue = 6244| pages = 733–737| date = October 26, 1989| doi = 10.1038/341733a0| bibcode=1989Natur.341..733G| s2cid = 4287597}}</ref>

===Volcanic activity===
{{main|Volcano tectonic earthquake}}

Earthquakes often occur in volcanic regions and are caused there, both by [[tectonic plates|tectonic]] faults and the movement of [[magma]] in [[volcano]]es. Such earthquakes can serve as an early warning of volcanic eruptions, as during the [[1980 eruption of Mount St. Helens]].<ref>{{Cite book|last=Foxworthy and Hill|year=1982|title=Volcanic Eruptions of 1980 at Mount St. Helens, The First 100 Days: USGS Professional Paper 1249}}</ref> Earthquake swarms can serve as markers for the location of the flowing magma throughout the volcanoes. These swarms can be recorded by [[seismometers]] and [[tiltmeter]]s (a device that measures ground slope) and used as sensors to predict imminent or upcoming eruptions.<ref>{{cite web|url=http://pubs.usgs.gov/gip/earthq1/volcano.html|title=Volcanoes and Earthquakes|publisher=United States Geological Survey|date=January 7, 1998|author=Watson, John|author2=Watson, Kathie|access-date=May 9, 2009|archive-date=March 26, 2009|archive-url=https://web.archive.org/web/20090326093352/http://pubs.usgs.gov/gip/earthq1/volcano.html|url-status=live}}</ref>

===Rupture dynamics===
A tectonic earthquake begins as an area of initial slip on the fault surface that forms the focus. Once the rupture has been initiated, it begins to propagate away from the focus, spreading out along the fault surface. Lateral propagation will continue until either the rupture reaches a barrier, such as the end of a fault segment, or a region on the fault where there is insufficient stress to allow continued rupture. For larger earthquakes, the depth extent of rupture will be constrained downwards by the [[brittle-ductile transition zone]] and upwards by the ground surface. The mechanics of this process are poorly understood because it is difficult either to recreate such rapid movements in a laboratory or to record seismic waves close to a nucleation zone due to strong ground motion.<ref name="NRS"/>

In most cases, the rupture speed approaches, but does not exceed, the [[S wave|shear wave]] (S wave) velocity of the surrounding rock. There are a few exceptions to this:

==== Supershear earthquakes ====
[[File:Kahramanmaraş after 7.8 magnitude earthquake in Türkiye 5.jpg|250px|thumb|right|The [[2023 Turkey–Syria earthquakes]] ruptured along segments of the [[East Anatolian Fault]] at supershear speeds; more than 50,000 people died in both countries.<ref name="MelgarEtAl23">{{cite journal |last1=Melgar |first1=Diego |last2=Taymaz |first2=Tuncay |last3=Ganas |first3=Athanassios |last4=Crowell |first4=Brendan |last5=Öcalan |first5=Taylan |last6=Kahraman |first6=Metin |last7=Tsironi |first7=Varvara |last8=Yolsal-Çevikbilen |first8=Seda |last9=Valkaniotis |first9=Sotiris |last10=Irmak |first10=Tahir Serkan |last11=Eken |first11=Tuna |last12=Erman |first12=Ceyhun |last13=Özkan |first13=Berkan |last14=Dogan |first14=Ali Hasan |last15=Altuntaş |first15=Cemali |title=Sub- and super-shear ruptures during the 2023 Mw 7.8 and Mw 7.6 earthquake doublet in SE Türkiye |journal=Seismica |year=2023 |volume=2 |issue=3 |page=387 |doi=10.26443/seismica.v2i3.387|s2cid=257520761 |doi-access=free |bibcode=2023Seism...2..387M }}</ref>]]
[[Supershear earthquake]] ruptures are known to have propagated at speeds greater than the S wave velocity. These have so far all been observed during large strike-slip events. The unusually wide zone of damage caused by the [[2001 Kunlun earthquake]] has been attributed to the effects of the [[sonic boom]] developed in such earthquakes.

==== Slow earthquakes ====
[[Slow earthquake]] ruptures travel at unusually low velocities. A particularly dangerous form of slow earthquake is the [[tsunami earthquake]], observed where the relatively low felt intensities, caused by the slow propagation speed of some great earthquakes, fail to alert the population of the neighboring coast, as in the [[1896 Sanriku earthquake]].<ref name="NRS">{{cite book|last=National Research Council (U.S.). Committee on the Science of Earthquakes|title=Living on an Active Earth: Perspectives on Earthquake Science|chapter-url=http://www.nap.edu/openbook.php?record_id=10493&page=282|access-date=8 July 2010|year=2003|publisher=National Academies Press|location=Washington, D.C.|isbn=978-0-309-06562-7|page=[https://archive.org/details/livingonactiveea0000unse/page/418 418]|chapter=5. Earthquake Physics and Fault-System Science|url=https://archive.org/details/livingonactiveea0000unse/page/418}}</ref>

====Co-seismic overpressuring and effect of pore pressure====
During an earthquake, high temperatures can develop at the fault plane, increasing pore pressure and consequently vaporization of the groundwater already contained within the rock.<ref name=Sibson>{{cite journal|last1=Sibson |first1= R.H.|year=1973|title=Interactions between Temperature and Pore-Fluid Pressure during Earthquake Faulting and a Mechanism for Partial or Total Stress Relief|journal= Nat. Phys. Sci. |volume=243|issue= 126|pages=66–68|doi= 10.1038/physci243066a0|bibcode= 1973NPhS..243...66S}}</ref><ref name=Rudnicki>{{cite journal|last1=Rudnicki |first1= J.W.|last2=Rice |first2= J.R.|year=2006|title=Effective normal stress alteration due to pore pressure changes induced by dynamic slip propagation on a plane between dissimilar materials|journal= J. Geophys. Res. |volume= 111, B10308|issue= B10|doi=10.1029/2006JB004396|bibcode= 2006JGRB..11110308R|s2cid= 1333820|url=https://dash.harvard.edu/bitstream/1/2668811/1/Rice_PorePressDynSlip.pdf|url-status=live|archive-url=https://web.archive.org/web/20190502041503/https://dash.harvard.edu/bitstream/handle/1/2668811/Rice_PorePressDynSlip.pdf;jsessionid=071046244FA1B0E26418CE95B726BA0E?sequence=1|archive-date=2019-05-02|archive-format=PDF}}</ref><ref name=Guerriero>{{cite journal|last1=Guerriero |first1= V |last2=Mazzoli |first2= S.|year=2021|title=Theory of Effective Stress in Soil and Rock and Implications for Fracturing Processes: A Review|journal=Geosciences |volume=11|issue= 3 |pages=119|doi=10.3390/geosciences11030119|bibcode= 2021Geosc..11..119G |doi-access=free}}</ref> In the coseismic phase, such an increase can significantly affect slip evolution and speed, in the post-seismic phase it can control the [[Aftershock]] sequence because, after the main event, pore pressure increase slowly propagates into the surrounding fracture network.<ref name=Nur>{{cite journal|last1=Nur |first1= A |last2=Booker |first2= J.R.|year=1972|title=Aftershocks Caused by Pore Fluid Flow?|journal=Science |volume=175|issue= 4024 |pages=885–887|doi= 10.1126/science.175.4024.885 |pmid= 17781062 |bibcode= 1972Sci...175..885N |s2cid= 19354081 }}</ref><ref name=Guerriero /> From the point of view of the [[Mohr-Coulomb theory|Mohr-Coulomb strength theory]], an increase in fluid pressure reduces the normal stress acting on the fault plane that holds it in place, and fluids can exert a lubricating effect. As thermal overpressurization may provide positive feedback between slip and strength fall at the fault plane, a common opinion is that it may enhance the faulting process instability. After the mainshock, the pressure gradient between the fault plane and the neighboring rock causes a fluid flow that increases pore pressure in the surrounding fracture networks; such an increase may trigger new faulting processes by reactivating adjacent faults, giving rise to aftershocks.<ref name=Nur /><ref name=Guerriero /> Analogously, artificial pore pressure increase, by fluid injection in Earth's crust, may [[Induced seismicity|induce seismicity]].

===Tidal forces===
{{main|Tidal triggering of earthquakes}}
[[Tides]] may trigger some [[seismicity]].<ref>{{cite journal | last1=Hartzell | first1=Stephen | last2=Heaton | first2=Thomas | title=The fortnightly tide and the tidal triggering of earthquakes | journal=Bulletin of the Seismological Society of America | volume=80 | issue=2 | date=1990-04-01 | issn=1943-3573 | doi=10.1785/BSSA0800020504 | doi-access=free | pages=504–505 | bibcode=1990BuSSA..80..504H | url=https://authors.library.caltech.edu/records/39ffh-nrm98/files/1282.full.pdf?download=1}}</ref>

===Clusters===
Most earthquakes form part of a sequence, related to each other in terms of location and time.<ref name=WAAFEC>{{cite web|url=https://earthquake.usgs.gov/eqcenter/step/explain.php|title=What are Aftershocks, Foreshocks, and Earthquake Clusters?|url-status=dead|archive-url=https://web.archive.org/web/20090511175245/http://earthquake.usgs.gov/eqcenter/step/explain.php|archive-date=2009-05-11}}</ref> Most earthquake clusters consist of small tremors that cause little to no damage, but there is a theory that earthquakes can recur in a regular pattern.<ref>{{cite web|url=https://earthquake.usgs.gov/research/parkfield/repeat.php|title=Repeating Earthquakes|publisher=United States Geological Survey|date=January 29, 2009|access-date=May 11, 2009|archive-date=April 3, 2009|archive-url=https://web.archive.org/web/20090403074132/http://earthquake.usgs.gov/research/parkfield/repeat.php|url-status=live}}</ref> Earthquake clustering has been observed, for example, in Parkfield, California where a long-term research study is being conducted around the [[Parkfield earthquake]] cluster.<ref>{{Cite web |title=The Parkfield, California, Earthquake Experiment |url=https://earthquake.usgs.gov/learn/parkfield/ |access-date=2022-10-24 |publisher=United States Geological Survey |archive-date=2022-10-24 |archive-url=https://web.archive.org/web/20221024200153/https://earthquake.usgs.gov/learn/parkfield/ |url-status=live }}</ref>

====Aftershocks====
{{Main|Aftershock}}
[[File:2016 Central Italy earthquake wide.svg|thumb|upright=1.25|Magnitude of the [[August 2016 Central Italy earthquake|Central Italy earthquakes of August]] and [[October 2016 Central Italy earthquakes|October 2016]] and [[January 2017 Central Italy earthquakes|January 2017]] and the aftershocks (which continued to occur after the period shown here)]]
An aftershock is an earthquake that occurs after a previous earthquake, the mainshock. Rapid changes of stress between rocks, and the stress from the original earthquake are the main causes of these aftershocks,<ref name=Britannica>{{Cite web|title=Aftershock {{!}} geology|url=https://www.britannica.com/science/aftershock-geology|access-date=2021-10-13|website=Encyclopædia Britannica|archive-date=2015-08-23|archive-url=https://web.archive.org/web/20150823124854/https://www.britannica.com/science/aftershock-geology|url-status=live}}</ref> along with the crust around the ruptured [[Fault (geology)|fault plane]] as it adjusts to the effects of the mainshock.<ref name="WAAFEC" /> An aftershock is in the same region as the main shock but always of a smaller magnitude, however, they can still be powerful enough to cause even more damage to buildings that were already previously damaged from the mainshock.<ref name=Britannica/> If an aftershock is larger than the mainshock, the aftershock is redesignated as the mainshock and the original main shock is redesignated as a [[foreshock]]. Aftershocks are formed as the crust around the displaced [[Fault (geology)|fault plane]] adjusts to the effects of the mainshock.<ref name=WAAFEC/>

====Swarms====
{{Main|Earthquake swarm}}
Earthquake swarms are sequences of earthquakes striking in a specific area within a short period. They are different from earthquakes followed by a series of [[aftershock]]s by the fact that no single earthquake in the sequence is the main shock, so none has a notably higher magnitude than another. An example of an earthquake swarm is the 2004 activity at [[Yellowstone National Park]].<ref>{{cite web|url=http://volcanoes.usgs.gov/yvo/2004/Apr04Swarm.html|title=Earthquake Swarms at Yellowstone|publisher=United States Geological Survey|access-date=2008-09-15|archive-date=2008-05-13|archive-url=https://web.archive.org/web/20080513060550/http://volcanoes.usgs.gov/yvo/2004/Apr04Swarm.html|url-status=live}}</ref> In August 2012, a swarm of earthquakes shook [[Southern California]]'s [[Imperial Valley]], showing the most recorded activity in the area since the 1970s.<ref>{{cite news|last=Duke|first=Alan|title=Quake 'swarm' shakes Southern California|url=http://www.cnn.com/2012/08/26/us/california-quake-swarm/index.html|publisher=CNN|access-date=27 August 2012|archive-date=27 August 2012|archive-url=https://web.archive.org/web/20120827120248/http://www.cnn.com/2012/08/26/us/california-quake-swarm/index.html|url-status=live}}</ref>

Sometimes a series of earthquakes occur in what has been called an ''earthquake storm'', where the earthquakes strike a fault in clusters, each triggered by the shaking or [[coulomb stress transfer|stress redistribution]] of the previous earthquakes. Similar to [[aftershock]]s but on adjacent segments of fault, these storms occur over the course of years, with some of the later earthquakes as damaging as the early ones. Such a pattern was observed in the sequence of about a dozen earthquakes that struck the [[North Anatolian Fault]] in Turkey in the 20th century and has been inferred for older anomalous clusters of large earthquakes in the Middle East.<ref>{{cite journal |title=Poseidon's Horses: Plate Tectonics and Earthquake Storms in the Late Bronze Age Aegean and Eastern Mediterranean |journal=Journal of Archaeological Science |year=2000 |author=Amos Nur |issn=0305-4403 |volume=27 |issue=1 |pages=43–63 |url=http://water.stanford.edu/nur/EndBronzeage.pdf |doi=10.1006/jasc.1999.0431 |last2=Cline |first2=Eric H. |bibcode=2000JArSc..27...43N |url-status=dead |archive-date=2009-03-25 |archive-url=https://web.archive.org/web/20090325050459/http://water.stanford.edu/nur/EndBronzeage.pdf}}</ref><ref>{{cite web |url=http://www.bbc.co.uk/science/horizon/2003/earthquakestorms.shtml |title=Earthquake Storms |work=[[Horizon (BBC TV series)|Horizon]] |date=1 April 2003 |access-date=2007-05-02 |archive-date=2019-10-16 |archive-url=https://web.archive.org/web/20191016045550/http://www.bbc.co.uk/science/horizon/2003/earthquakestorms.shtml |url-status=live }}</ref>

===Frequency===
[[File:Comerio, Luca (1878-1940) - Vittime del terremoto di Messina (dicembre 1908).jpg|thumb|The [[1908 Messina earthquake|Messina earthquake]] and tsunami took about 80,000 lives on December 28, 1908, in [[Sicily]] and [[Calabria]].<ref name="CFTI5">{{Cite web |url=https://storing.ingv.it/cfti/cfti5/quake.php?21318IT |title=1908 12 28, 04:20:27 Calabria meridionale-Messina (Italy) |last1=Guidoboni E. |last2= Ferrari G. |website=CFTI5 Catalogue of Strong Earthquakes in Italy (461 BC – 1997) and Mediterranean Area (760 B.C. – 1500) |last3=Mariotti D. |last4=Comastri A. |last5=Tarabusi G. |last6=Sgattoni G. |last7=Valensise G}}</ref>]]

It is estimated that around 500,000 earthquakes occur each year, detectable with current instrumentation. About 100,000 of these can be felt.<ref name="usgsfacts">{{cite web|url=https://www.usgs.gov/natural-hazards/earthquake-hazards/science/cool-earthquake-facts|title=Cool Earthquake Facts|publisher=United States Geological Survey|access-date=2021-04-21|archive-date=2021-04-20|archive-url=https://web.archive.org/web/20210420165152/https://www.usgs.gov/natural-hazards/earthquake-hazards/science/cool-earthquake-facts|url-status=live}}</ref><ref name="wp100414">{{Cite news | first=Margaret Webb | last=Pressler | title=More earthquakes than usual? Not really. | department=KidsPost | newspaper= The Washington Post| pages= C10 | date=14 April 2010 }}</ref> Minor earthquakes occur very frequently around the world in places like California and Alaska in the U.S., as well as in El Salvador, Mexico, Guatemala, Chile, Peru, Indonesia, the Philippines, Iran, Pakistan, the [[Azores]] in Portugal, Turkey, New Zealand, Greece, Italy, India, Nepal, and Japan.<ref>{{cite web |url=https://earthquake.usgs.gov/ |title=Earthquake Hazards Program |publisher=United States Geological Survey |access-date=2006-08-14 |archive-date=2011-05-13 |archive-url=https://web.archive.org/web/20110513032733/https://earthquake.usgs.gov/ |url-status=live }}</ref> Larger earthquakes occur less frequently, the relationship being [[Gutenberg–Richter law|exponential]]; for example, roughly ten times as many earthquakes larger than magnitude 4 occur than earthquakes larger than magnitude 5.<ref>{{Cite web|url=https://earthquake.usgs.gov/earthquakes/eqarchives/year/eqstats.php|archiveurl=https://web.archive.org/web/20100524161817/http://earthquake.usgs.gov/earthquakes/eqarchives/year/eqstats.php|url-status=dead|title=USGS Earthquake statistics table based on data since 1900|archivedate=May 24, 2010}}</ref> In the (low seismicity) United Kingdom, for example, it has been calculated that the average recurrences are:
an earthquake of 3.7–4.6 every year, an earthquake of 4.7–5.5 every 10 years, and an earthquake of 5.6 or larger every 100 years.<ref>{{cite web |url=http://www.quakes.bgs.ac.uk/hazard/Hazard_UK.htm |title=Seismicity and earthquake hazard in the UK |publisher=Quakes.bgs.ac.uk |access-date=2010-08-23 |archive-date=2010-11-06 |archive-url=https://web.archive.org/web/20101106121058/http://quakes.bgs.ac.uk/hazard/Hazard_UK.htm |url-status=live }}</ref> This is an example of the [[Gutenberg–Richter law]].

The number of seismic stations has increased from about 350 in 1931 to many thousands today. As a result, many more earthquakes are reported than in the past, but this is because of the vast improvement in instrumentation, rather than an increase in the number of earthquakes. The [[United States Geological Survey]] (USGS) estimates that, since 1900, there have been an average of 18 major earthquakes (magnitude 7.0–7.9) and one great earthquake (magnitude 8.0 or greater) per year, and that this average has been relatively stable.<ref>
{{cite web
|title = Common Myths about Earthquakes
|url = https://earthquake.usgs.gov/learning/faq.php?categoryID=6&faqID=110
|publisher = United States Geological Survey
|access-date = 2006-08-14
|url-status = dead
|archive-url = https://web.archive.org/web/20060925135349/http://earthquake.usgs.gov/learning/faq.php?categoryID=6&faqID=110
|archive-date = 2006-09-25
}}</ref> In recent years, the number of major earthquakes per year has decreased, though this is probably a statistical fluctuation rather than a systematic trend.<ref>[https://earthquake.usgs.gov/learn/topics/increase_in_earthquakes.php Are Earthquakes Really on the Increase?] {{webarchive|url=https://web.archive.org/web/20140630233346/http://earthquake.usgs.gov/learn/topics/increase_in_earthquakes.php |date=2014-06-30 }}, USGS Science of Changing World. Retrieved 30 May 2014.</ref> More detailed statistics on the size and frequency of earthquakes is available from the United States Geological Survey.<ref>
{{cite web
|title=Earthquake Facts and Statistics: Are earthquakes increasing?
|url=http://neic.usgs.gov/neis/eqlists/eqstats.html
|publisher=United States Geological Survey
|access-date=2006-08-14
|url-status=dead
|archive-url=https://web.archive.org/web/20060812060818/http://neic.usgs.gov/neis/eqlists/eqstats.html
|archive-date=2006-08-12
}}</ref> A recent increase in the number of major earthquakes has been noted, which could be explained by a cyclical pattern of periods of intense tectonic activity, interspersed with longer periods of low intensity. However, accurate recordings of earthquakes only began in the early 1900s, so it is too early to categorically state that this is the case.<ref>[http://www.australiangeographic.com.au/journal/the-10-biggest-earthquakes-in-recorded-history.htm/ The 10 biggest earthquakes in history] {{Webarchive|url=https://web.archive.org/web/20130930084024/http://www.australiangeographic.com.au/journal/the-10-biggest-earthquakes-in-recorded-history.htm/ |date=2013-09-30 }}, Australian Geographic, March 14, 2011.</ref>

Most of the world's earthquakes (90%, and 81% of the largest) take place in the {{convert|40000|km|mi|adj=mid|-long}}, horseshoe-shaped zone called the circum-Pacific seismic belt, known as the Pacific [[Ring of Fire]], which for the most part bounds the [[Pacific plate]].<ref>
{{cite web
|title = Historic Earthquakes and Earthquake Statistics: Where do earthquakes occur?
|url = https://earthquake.usgs.gov/learning/faq.php?categoryID=11&faqID=95
|publisher = United States Geological Survey
|access-date = 2006-08-14
|url-status = dead
|archive-url = https://web.archive.org/web/20060925142008/http://earthquake.usgs.gov/learning/faq.php?categoryID=11&faqID=95
|archive-date = 2006-09-25
}}</ref><ref>
{{cite web
|url = https://earthquake.usgs.gov/learning/glossary.php?termID=150
|publisher = United States Geological Survey
|title = Visual Glossary – Ring of Fire
|access-date = 2006-08-14
|url-status = dead
|archive-url = https://web.archive.org/web/20060828152638/http://earthquake.usgs.gov/learning/glossary.php?termID=150
|archive-date = 2006-08-28
}}</ref> Massive earthquakes tend to occur along other plate boundaries too, such as along the [[Himalayan Mountains]].<ref>{{cite journal | last1 = Jackson | first1 = James | year = 2006 | title = Fatal attraction: living with earthquakes, the growth of villages into megacities, and earthquake vulnerability in the modern world | url = http://rsta.royalsocietypublishing.org/content/364/1845/1911.full | journal = [[Philosophical Transactions of the Royal Society]] | volume = 364 | issue = 1845 | pages = 1911–1925 | doi = 10.1098/rsta.2006.1805 | pmid = 16844641 | bibcode = 2006RSPTA.364.1911J | s2cid = 40712253 | access-date = 2011-03-09 | archive-date = 2013-09-03 | archive-url = https://web.archive.org/web/20130903085953/http://rsta.royalsocietypublishing.org/content/364/1845/1911.full | url-status = live | url-access = subscription }}</ref>

With the rapid growth of [[Megacity|mega-cities]] such as Mexico City, Tokyo, and Tehran in areas of high [[seismic risk]], some seismologists are warning that a single earthquake may claim the lives of up to three million people.<ref>"[http://cires.colorado.edu/~bilham/UrbanEarthquakesGlobal.html Global urban seismic risk] {{Webarchive|url=https://web.archive.org/web/20110920015358/http://cires.colorado.edu/~bilham/UrbanEarthquakesGlobal.html |date=2011-09-20 }}." Cooperative Institute for Research in Environmental Science.</ref>

===Induced seismicity===
{{main|Induced seismicity}}
While most earthquakes are caused by the movement of the Earth's [[tectonic plate]]s, human activity can also produce earthquakes. Activities both above ground and below may change the stresses and strains on the crust, including building reservoirs, extracting resources such as coal or oil, and injecting fluids underground for waste disposal or [[fracking]].<ref>{{cite journal |author1=Fougler, Gillian R. |author2=Wilson, Miles |author3=Gluyas, Jon G. |author4=Julian, Bruce R. |author5=Davies, Richard J. |author-link1=Gillian Foulger |title=Global review of human-induced earthquakes |journal=[[Earth-Science Reviews]] |date=2018 |volume=178 |pages=438–514 |doi=10.1016/j.earscirev.2017.07.008 |bibcode=2018ESRv..178..438F |doi-access=free }}</ref> Most of these earthquakes have small magnitudes. The 5.7 magnitude [[2011 Oklahoma earthquake]] is thought to have been caused by disposing wastewater from oil production into [[injection wells]],<ref>{{cite news |last1=Fountain |first1=Henry |title=Study Links 2011 Quake to Technique at Oil Wells |newspaper=The New York Times |url=https://www.nytimes.com/2013/03/29/science/earth/2011-oklahoma-quake-tied-to-wastewater-disposal-at-oil-wells.html |access-date=July 23, 2020 |date=March 28, 2013 |archive-date=July 23, 2020 |archive-url=https://web.archive.org/web/20200723135240/https://www.nytimes.com/2013/03/29/science/earth/2011-oklahoma-quake-tied-to-wastewater-disposal-at-oil-wells.html |url-status=live }}</ref> and studies point to the state's oil industry as the cause of other earthquakes in the past century.<ref>{{cite journal |author1=Hough, Susan E. |author-link1=Susan Hough |author2=Page, Morgan |title=A Century of Induced Earthquakes in Oklahoma? |journal=[[Bulletin of the Seismological Society of America]] |date=2015 |volume=105 |issue=6 |pages=2863–2870 |doi=10.1785/0120150109 |bibcode=2015BuSSA.105.2863H |url=https://pubs.geoscienceworld.org/ssa/bssa/article-abstract/105/6/2863/331910/A-Century-of-Induced-Earthquakes-in-Oklahoma-A?redirectedFrom=fulltext |access-date=July 23, 2020 |archive-date=July 23, 2020 |archive-url=https://web.archive.org/web/20200723210546/https://pubs.geoscienceworld.org/ssa/bssa/article-abstract/105/6/2863/331910/A-Century-of-Induced-Earthquakes-in-Oklahoma-A?redirectedFrom=fulltext |url-status=live |url-access=subscription }}</ref> A [[Columbia University]] paper suggested that the 8.0 magnitude [[2008 Sichuan earthquake]] was induced by loading from the [[Zipingpu Dam]],<ref>{{cite journal |last1=Klose |first1=Christian D. |title=Evidence for anthropogenic surface loading as trigger mechanism of the 2008 Wenchuan earthquake |journal=Environmental Earth Sciences |date=July 2012 |volume=66 |issue=5 |pages=1439–1447 |doi=10.1007/s12665-011-1355-7|arxiv=1007.2155 |bibcode=2012EES....66.1439K |s2cid=118367859 }}</ref> though the link has not been conclusively proved.<ref>{{cite news |last1=LaFraniere |first1=Sharon |title=Possible Link Between Dam and China Quake |newspaper=The New York Times |url=https://www.nytimes.com/2009/02/06/world/asia/06quake.html |access-date=July 23, 2020 |date=February 5, 2009 |archive-date=January 27, 2018 |archive-url=https://web.archive.org/web/20180127101432/http://www.nytimes.com/2009/02/06/world/asia/06quake.html |url-status=live }}</ref>

==Measurement and location==
{{Main|Seismic magnitude scales|Seismology}}

The instrumental scales used to describe the size of an earthquake began with the [[Richter scale]] in the 1930s. It is a relatively simple measurement of an event's amplitude, and its use has become minimal in the 21st century. [[Seismic waves]] travel through the [[Earth's interior]] and can be recorded by [[seismometer]]s at great distances. The [[surface-wave magnitude]] was developed in the 1950s as a means to measure remote earthquakes and to improve the accuracy for larger events. The [[moment magnitude scale]] not only measures the amplitude of the shock but also takes into account the [[seismic moment]] (total rupture area, average slip of the fault, and rigidity of the rock). The [[Japan Meteorological Agency seismic intensity scale]], the [[Medvedev–Sponheuer–Karnik scale]], and the [[Mercalli intensity scale]] are based on the observed effects and are related to the intensity of shaking.

=== {{anchor|Magnitude}}Intensity and magnitude ===
The shaking of the earth is a common phenomenon that has been experienced by humans from the earliest of times. Before the development of strong-motion accelerometers, the intensity of a seismic event was estimated based on the observed effects. Magnitude and intensity are not directly related and calculated using different methods. The magnitude of an earthquake is a single value that describes the size of the earthquake at its source. Intensity is the measure of shaking at different locations around the earthquake. Intensity values vary from place to place, depending on the distance from the earthquake and the underlying rock or soil makeup.<ref>{{Cite book |last1=Earle |first1=Steven |date=September 2015 |title=Physical Geology |edition=2nd |chapter=11.3 Measuring Earthquakes |chapter-url=https://opentextbc.ca/geology/chapter/11-3-measuring-earthquakes/|access-date=2022-10-22 |archive-date=2022-10-21 |archive-url=https://web.archive.org/web/20221021040843/https://opentextbc.ca/geology/chapter/11-3-measuring-earthquakes/ |url-status=live }}</ref>

The [[Seismic magnitude scales#Richter|first scale for measuring earthquake magnitudes]] was developed by [[Charles Francis Richter]] in 1935. Subsequent scales ([[seismic magnitude scales]]) have retained a key feature, where each unit represents a ten-fold difference in the amplitude of the ground shaking and a 32-fold difference in energy. Subsequent scales are also adjusted to have approximately the same numeric value within the limits of the scale.<ref>{{Harvnb|Chung|Bernreuter|1980|p=1}}.</ref>

Although the mass media commonly reports earthquake magnitudes as "Richter magnitude" or "Richter scale", standard practice by most seismological authorities is to express an earthquake's strength on the [[seismic scale#Mw|moment magnitude]] scale, which is based on the actual energy released by an earthquake, the static seismic moment.<ref>{{cite web |title=USGS Earthquake Magnitude Policy (implemented on January 18, 2002) |url=https://earthquake.usgs.gov/aboutus/docs/020204mag_policy.php |publisher=United States Geological Survey |url-status=dead |archive-url=https://web.archive.org/web/20160504144754/http://earthquake.usgs.gov/aboutus/docs/020204mag_policy.php |archive-date=2016-05-04 }} A copy can be found at {{cite web |title=USGS Earthquake Magnitude Policy |url=http://dapgeol.tripod.com/usgsearthquakemagnitudepolicy.htm |access-date=2017-07-25 |archive-date=2017-07-31 |archive-url=https://web.archive.org/web/20170731230704/http://dapgeol.tripod.com/usgsearthquakemagnitudepolicy.htm |url-status=live }}</ref><ref>{{Cite journal |last1=Bormann |first1=P |last2=Di Giacomo |first2=D |date=2011 |title=The moment magnitude Mw and the energy magnitude Me: common roots and differences |url=https://doi.org/10.1007/s10950-010-9219-2 |journal=Journal of Seismology |volume=15 |issue=2 |pages=411–427 |doi=10.1007/s10950-010-9219-2 |via=Springer Link}}</ref>

=== Seismic waves ===
Every earthquake produces different types of seismic waves, which travel through rock with different velocities:
* Longitudinal [[P waves]] (shock- or pressure waves)
* Transverse [[S waves]] (both body waves)
* [[Surface wave]]s – ([[Rayleigh wave|Rayleigh]] and [[Love wave]]s)

==== Speed of seismic waves ====
[[Propagation velocity]] of the seismic waves through solid rock ranges from approx. {{Convert|3|km/s|mi/s|abbr=on}} up to {{Convert|13|km/s|mi/s|abbr=on}}, depending on the [[density]] and [[Elasticity (physics)|elasticity]] of the medium. In the Earth's interior, the shock- or P waves travel much faster than the S waves (approx. relation 1.7:1). The differences in travel time from the [[epicentre|epicenter]] to the observatory are a measure of the distance and can be used to image both sources of earthquakes and structures within the Earth. Also, the depth of the [[hypocenter]] can be computed roughly.

'''P wave speed'''
* Upper crust soils and unconsolidated sediments: {{Convert|2-3|km|mi|abbr=on}} per second
* Upper crust solid rock: {{Convert|3-6|km|mi|abbr=on}} per second
* Lower crust: {{Convert|6-7|km|mi|abbr=on}} per second
* Deep mantle: {{Convert|13|km|mi|abbr=on}} per second.

'''S waves speed'''
* Light sediments: {{Convert|2-3|km|mi|abbr=on}} per second
* Earths crust: {{Convert|4-5|km|mi|abbr=on}} per second
* Deep mantle: {{Convert|7|km|mi|abbr=on}} per second

==== Seismic wave arrival ====
As a consequence, the first waves of a distant earthquake arrive at an observatory via the Earth's mantle.

On average, the kilometer distance to the earthquake is the number of seconds between the P- and S wave arrival times, multiplied by 8.<ref>{{cite web |url=http://hypertextbook.com/facts/2001/PamelaSpiegel.shtml |title=Speed of Sound through the Earth |publisher=Hypertextbook.com |access-date=2010-08-23 |archive-date=2010-11-25 |archive-url=https://web.archive.org/web/20101125091130/http://hypertextbook.com/facts/2001/PamelaSpiegel.shtml |url-status=live }}</ref> Slight deviations are caused by inhomogeneities of subsurface structure. By such analysis of seismograms, the Earth's core was located in 1913 by [[Beno Gutenberg]].

S waves and later arriving surface waves do most of the damage compared to P waves. P waves squeeze and expand the material in the same direction they are traveling, whereas S waves shake the ground up and down and back and forth.<ref>{{cite web|url=https://newsela.com/articles/govt-science-earthquakes/id/26756/|title=Newsela {{!}} The science of earthquakes|website=newsela.com|access-date=2017-02-28|archive-date=2017-03-01|archive-url=https://web.archive.org/web/20170301005337/https://newsela.com/articles/govt-science-earthquakes/id/26756/|url-status=live}}</ref>

=== Location and reporting ===
{{main|Epicenter}}

Earthquakes are not only categorized by their magnitude but also by the place where they occur. The world is divided into 754 [[Flinn–Engdahl regions]] (F-E regions), which are based on political and geographical boundaries as well as seismic activity. More active zones are divided into smaller F-E regions whereas less active zones belong to larger F-E regions.

Standard reporting of earthquakes includes its [[Richter magnitude scale|magnitude]], date and time of occurrence, [[geographic coordinates]] of its [[epicenter]], depth of the epicenter, geographical region, distances to population centers, location uncertainty, several parameters that are included in USGS earthquake reports (number of stations reporting, number of observations, etc.), and a unique event ID.<ref>{{cite web |url=http://geographic.org/earthquakes/real_time_details.php?id=recenteqsww/Quakes/usc000f1s0.php&lat=-10.7377&lon=165.1378 |title=Magnitude 8.0 – SANTA CRUZ ISLANDS Earthquake Details |work=Global Earthquake Epicenters with Maps |author=Geographic.org |access-date=2013-03-13 |archive-date=2013-05-14 |archive-url=https://web.archive.org/web/20130514143205/http://geographic.org/earthquakes/real_time_details.php?id=recenteqsww/Quakes/usc000f1s0.php&lat=-10.7377&lon=165.1378 |url-status=live }}</ref>

Although relatively slow seismic waves have traditionally been used to detect earthquakes, scientists realized in 2016 that gravitational measurement could provide instantaneous detection of earthquakes, and confirmed this by analyzing gravitational records associated with the [[2011 Tōhoku earthquake and tsunami|2011 Tohoku-Oki]] ("Fukushima") earthquake.<ref>{{cite web|url=https://www.researchgate.net/blog/post/changes-to-earths-gravity-offer-early-earthquake-warning|title=Earth's gravity offers earlier earthquake warnings|access-date=2016-11-22|archive-date=2016-11-23|archive-url=https://web.archive.org/web/20161123201125/https://www.researchgate.net/blog/post/changes-to-earths-gravity-offer-early-earthquake-warning|url-status=live}}</ref><ref>{{cite web|url=https://cosmosmagazine.com/geoscience/gravity-shifts-could-sound-early-earthquake-alarm|title=Gravity shifts could sound early earthquake alarm|access-date=2016-11-23|archive-date=2016-11-24|archive-url=https://web.archive.org/web/20161124100006/https://cosmosmagazine.com/geoscience/gravity-shifts-could-sound-early-earthquake-alarm|url-status=dead}}</ref>

==Effects==
[[File:1755 Lisbon earthquake.jpg|thumb|1755 copper engraving depicting [[Lisbon]] in ruins and in flames after the [[1755 Lisbon earthquake]], which killed an estimated 60,000 people. A [[tsunami]] overwhelms the ships in the harbor.]]

The effects of earthquakes include, but are not limited to, the following:

===Shaking and ground rupture===
[[File:Haiti earthquake damage.jpg|thumb|Damaged buildings in [[Port-au-Prince]], [[2010 Haiti earthquake|Haiti]], January 2010]]

Shaking and [[surface rupture|ground rupture]] are the main effects created by earthquakes, principally resulting in more or less severe damage to buildings and other rigid structures. The severity of the local effects depends on the complex combination of the earthquake [[Richter magnitude scale|magnitude]], the distance from the [[epicenter]], and the local geological and geomorphological conditions, which may amplify or reduce [[wave propagation]].<ref>{{cite web |url=http://www.abag.ca.gov/bayarea/eqmaps/doc/contents.html |title=On Shaky Ground, Association of Bay Area Governments, San Francisco, reports 1995, 1998 (updated 2003) |publisher=Abag.ca.gov |access-date=2010-08-23 |url-status=dead |archive-url=https://web.archive.org/web/20090921082202/http://www.abag.ca.gov/bayarea/eqmaps/doc/contents.html |archive-date=2009-09-21 }}</ref> The ground-shaking is measured by [[ground acceleration]].

Specific local geological, geomorphological, and geostructural features can induce high levels of shaking on the ground surface even from low-intensity earthquakes. This effect is called site or local amplification. It is principally due to the transfer of the [[seismic]] motion from hard deep soils to soft superficial soils and the effects of seismic energy focalization owing to the typical geometrical setting of such deposits.

Ground rupture is a visible breaking and displacement of the Earth's surface along the trace of the fault, which may be of the order of several meters in the case of major earthquakes. Ground rupture is a major risk for large engineering structures such as [[dams]], bridges, and [[nuclear power stations]] and requires careful mapping of existing faults to identify any that are likely to break the ground surface within the life of the structure.<ref>{{cite web|url=http://www.consrv.ca.gov/cgs/information/publications/cgs_notes/note_49/Documents/note_49.pdf|title=Guidelines for evaluating the hazard of surface fault rupture, California Geological Survey|publisher=California Department of Conservation|year=2002|url-status=dead|archive-url=https://web.archive.org/web/20091009065422/http://www.consrv.ca.gov/cgs/information/publications/cgs_notes/note_49/Documents/note_49.pdf|archive-date=2009-10-09}}</ref>

===Soil liquefaction===
{{Main|Soil liquefaction}}
Soil liquefaction occurs when, because of the shaking, water-saturated [[granular]] material (such as sand) temporarily loses its strength and transforms from a solid to a liquid. Soil liquefaction may cause rigid structures, like buildings and bridges, to tilt or sink into the liquefied deposits. For example, in the [[1964 Alaska earthquake]], soil liquefaction caused many buildings to sink into the ground, eventually collapsing upon themselves.<ref>{{cite web|url=https://earthquake.usgs.gov/regional/states/events/1964_03_28.php |title=Historic Earthquakes – 1964 Anchorage Earthquake |publisher=United States Geological Survey |access-date=2008-09-15 |url-status=dead |archive-url=https://web.archive.org/web/20110623111831/http://earthquake.usgs.gov/regional/states/events/1964_03_28.php |archive-date=2011-06-23 }}</ref>

===Human impacts===
[[File:Ghajn Hadid Tower closer view.JPG|thumb|Ruins of the [[Għajn Ħadid Tower]], which collapsed during the [[1856 Heraklion earthquake]]]]

Physical damage from an earthquake will vary depending on the intensity of shaking in a given area and the type of population. Underserved and developing communities frequently experience more severe impacts (and longer lasting) from a seismic event compared to well-developed communities.<ref>{{Cite web |title=The wicked problem of earthquake hazard in developing countries |url=https://www.preventionweb.net/news/wicked-problem-earthquake-hazard-developing-countries |access-date=2022-11-03 |website=preventionweb.net |date=7 March 2018|archive-date=2022-11-03 |archive-url=https://web.archive.org/web/20221103025507/https://www.preventionweb.net/news/wicked-problem-earthquake-hazard-developing-countries |url-status=live }}</ref> Impacts may include:
* Injuries and loss of life
* Damage to critical infrastructure (short and long-term)
** Roads, bridges, and public transportation networks
** Water, power, sewer and gas interruption
** Communication systems
* Loss of critical community services including hospitals, police, and fire
* General [[property damage]]
* Collapse or destabilization (potentially leading to future collapse) of buildings

With these impacts and others, the aftermath may bring disease, a lack of basic necessities, mental consequences such as panic attacks and depression to survivors,<ref>{{cite web |url=http://www.nctsn.org/trauma-types/natural-disasters/earthquakes |title=Earthquake Resources |date=30 January 2018 |publisher=Nctsn.org |access-date=2018-06-05 |archive-date=2018-03-21 |archive-url=https://web.archive.org/web/20180321183320/http://www.nctsn.org/trauma-types/natural-disasters/earthquakes |url-status=live }}</ref> and higher insurance premiums. Recovery times will vary based on the level of damage and the socioeconomic status of the impacted community.

===Landslides===
{{further|Landslide}}

China stood out in several categories in a study group of 162 earthquakes (from 1772 to 2021) that included landslide fatalities. Due to the [[2008 Sichuan earthquake]], it had 42% of all landslide fatalities within the study (total event deaths were higher). They were followed by Peru (22%) from the [[1970 Ancash earthquake]], and Pakistan (21%) from the [[2005 Kashmir earthquake]]. China was also on top with the highest area affected by landslides with more than 80,000 km2, followed by Canada with 66,000 km2 ([[1988 Saguenay earthquake|1988 Saguenay]] and [[1946 Vancouver Island earthquake|1946 Vancouver Island]]). Strike-slip (61 events) was the dominant fault type listed, followed closely by thrust/reverse (57), and normal (33).<ref>{{citation | last1=Seal | first1=Dylan M | last2=Jessee | first2=Anna Nowicki | last3=Hamburger | first3=Michael | last4=Dills | first4=Carter | last5=Allstadt | first5=Kate E | title=Comprehensive Global Database of Earthquake-Induced Landslide Events and Their Impacts (ver. 2.0, February 2022) | date=2022 | publisher=U.S. Geological Survey | doi=10.5066/P9RG3MBE}}</ref>

===Fires===
[[File:Sfearthquake3b.jpg|thumb|Fires of the [[1906 San Francisco earthquake]]]]
{{Further|Conflagration}}

Earthquakes can cause fires by damaging [[electric power|electrical power]] or gas lines. In the event of water mains rupturing and a loss of pressure, it may also become difficult to stop the spread of a fire once it has started. For example, more deaths in the [[1906 San Francisco earthquake]] were caused by fire than by the earthquake itself.<ref>{{cite web|url=https://earthquake.usgs.gov/regional/nca/1906/18april/index.php|title=The Great 1906 San Francisco earthquake of 1906|publisher=United States Geological Survey|access-date=2008-09-15|archive-date=2017-02-11|archive-url=https://web.archive.org/web/20170211170826/https://earthquake.usgs.gov/regional/nca/1906/18april/index.php|url-status=dead}}</ref>

===Tsunami===
[[File:2004-tsunami.jpg|thumb|The tsunami of the [[2004 Indian Ocean earthquake]]]]
{{main|Tsunami}}

Tsunamis are long-wavelength, long-period sea waves produced by the sudden or abrupt movement of large volumes of water—including when an earthquake [[Submarine earthquake|occurs at sea]]. In the open ocean, the distance between wave crests can surpass {{convert|100|km|mi}}, and the wave periods can vary from five minutes to one hour. Such tsunamis travel 600–800 kilometers per hour (373–497 miles per hour), depending on water depth. Large waves produced by an earthquake or a submarine landslide can overrun nearby coastal areas in a matter of minutes. Tsunamis can also travel thousands of kilometers across open ocean and wreak destruction on far shores hours after the earthquake that generated them.<ref name=Noson>{{Cite book|last1=Noson|first1=L.L.|last2=Qamar|first2=A.|last3=Thorsen|first3=G.W.|publisher=Washington State Earthquake Hazards|year=1988|title=Washington Division of Geology and Earth Resources Information Circular 85|url=http://file.dnr.wa.gov/publications/ger_ic85_earthquake_hazards_wa.pdf|access-date=2019-12-01|archive-date=2020-02-04|archive-url=https://web.archive.org/web/20200204162651/https://file.dnr.wa.gov/publications/ger_ic85_earthquake_hazards_wa.pdf|url-status=live}}</ref>

Ordinarily, subduction earthquakes under magnitude 7.5 do not cause tsunamis, although some instances of this have been recorded. Most destructive tsunamis are caused by earthquakes of magnitude 7.5 or more.<ref name=Noson/>

===Floods===
{{further|Flood}}

Floods may be secondary effects of earthquakes if dams are damaged. Earthquakes may cause landslips to dam rivers, which collapse and cause floods.<ref>{{cite web|url=http://www.quakes.bgs.ac.uk/earthquakes/historical/historical_listing.htm |title=Notes on Historical Earthquakes |publisher=[[British Geological Survey]] |access-date=2008-09-15 |url-status=dead |archive-url=https://web.archive.org/web/20110516173115/http://www.quakes.bgs.ac.uk/earthquakes/historical/historical_listing.htm |archive-date=2011-05-16 }}</ref>

The terrain below the [[Sarez Lake]] in Tajikistan is in danger of catastrophic flooding if the [[landslide dam]] formed by the earthquake, known as the [[Usoi Dam]], were to fail during a future earthquake. Impact projections suggest the flood could affect roughly five million people.<ref>{{cite news|url=http://news.bbc.co.uk/2/hi/asia-pacific/3120693.stm|title=Fresh alert over Tajik flood threat|date=2003-08-03|publisher=BBC News|access-date=2008-09-15|archive-date=2008-11-22|archive-url=https://web.archive.org/web/20081122134305/http://news.bbc.co.uk/2/hi/asia-pacific/3120693.stm|url-status=live}}</ref>

==Management==

===Prediction===
{{Main|Earthquake prediction}}

[[Earthquake prediction]] is a branch of the science of [[seismology]] concerned with the specification of the time, location, and [[seismic scale|magnitude]] of future earthquakes within stated limits.<ref>{{Harvnb|Geller|Jackson|Kagan|Mulargia|1997|p=1616}}, following {{Harvtxt|Allen|1976|p=2070}}, who in turn followed {{Harvtxt|Wood|Gutenberg|1935}}</ref> Many methods have been developed for predicting the time and place in which earthquakes will occur. Despite considerable research efforts by [[seismologist]]s, scientifically reproducible predictions cannot yet be made to a specific day or month.<ref name="ludwin">[http://www.geophys.washington.edu/SEIS/PNSN/INFO_GENERAL/eq_prediction.html Earthquake Prediction] {{Webarchive|url=https://web.archive.org/web/20091007165545/http://www.geophys.washington.edu/SEIS/PNSN/INFO_GENERAL/eq_prediction.html |date=2009-10-07 }}. Ruth Ludwin, U.S. Geological Survey.</ref> Popular belief holds earthquakes are preceded by [[earthquake weather]], in the early morning.<ref>{{Cite news |last=Lafee |first=Scott |date=April 9, 2010 |title=Quake myths rely on cloudy facts |url=https://www.sandiegouniontribune.com/2010/04/09/quake-myths-rely-on-cloudy-facts/ |access-date=July 3, 2024 |work=[[The San Diego Union-Tribune]]}}</ref><ref>{{Cite web |title=Is there earthquake weather? |url=https://www.usgs.gov/faqs/there-earthquake-weather |url-status=live |archive-url=https://web.archive.org/web/20240303155939/https://www.usgs.gov/faqs/there-earthquake-weather |archive-date=March 3, 2024 |access-date=July 3, 2024 |publisher=United States Geological Survey}}</ref>

===Forecasting===
{{Main|Earthquake forecasting}}

While [[forecasting]] is usually considered to be a type of [[prediction]], [[earthquake forecasting]] is often differentiated from [[earthquake prediction]]. Earthquake forecasting is concerned with the probabilistic assessment of general earthquake hazards, including the frequency and magnitude of damaging earthquakes in a given area over years or decades.<ref>{{Harvnb|Kanamori|2003}}, p. 1205. See also {{Harvnb|International Commission on Earthquake Forecasting for Civil Protection|2011}}, p. 327.</ref> For well-understood faults the probability that a segment may rupture during the next few decades can be estimated.<ref>Working Group on California Earthquake Probabilities in the San Francisco Bay Region, 2003 to 2032, 2003, {{cite web |title=Bay Area Earthquake Probabilities|url=https://earthquake.usgs.gov/regional/nca/wg02/index.php |access-date=2017-08-28 |url-status=dead |archive-url=https://web.archive.org/web/20170218174649/http://earthquake.usgs.gov/regional/nca/wg02/index.php |archive-date=2017-02-18 }}</ref><ref>{{Cite journal|last=Pailoplee|first=Santi|date=2017-03-13|title=Probabilities of Earthquake Occurrences along the Sumatra-Andaman Subduction Zone|journal=Open Geosciences|volume=9|issue=1|pages=4|doi=10.1515/geo-2017-0004|issn=2391-5447|bibcode=2017OGeo....9....4P|s2cid=132545870|doi-access=free}}</ref>

[[Earthquake warning system]]s have been developed that can provide regional notification of an earthquake in progress, but before the ground surface has begun to move, potentially allowing people within the system's range to seek shelter before the earthquake's impact is felt.

===Preparedness===
{{main|Earthquake preparedness}}

The objective of [[earthquake engineering]] is to foresee the impact of earthquakes on buildings, bridges, tunnels, roadways, and other structures, and to design such structures to minimize the risk of damage. Existing structures can be modified by [[seismic retrofitting]] to improve their resistance to earthquakes. [[Earthquake insurance]] can provide building owners with financial protection against losses resulting from earthquakes. [[Emergency management]] strategies can be employed by a government or organization to mitigate risks and prepare for consequences.

[[Artificial intelligence]] may help to assess buildings and plan precautionary operations. The Igor [[expert system]] is part of a mobile laboratory that supports the procedures leading to the seismic assessment of masonry buildings and the planning of retrofitting operations on them. It has been applied to assess buildings in [[Lisbon]], [[Rhodes]], and [[Naples]].<ref>{{Cite journal|last1=Salvaneschi|first1=P.|last2=Cadei|first2=M.|last3=Lazzari|first3=M.|date=1996|title=Applying AI to Structural Safety Monitoring and Evaluation|journal=IEEE Expert|volume=11|issue=4|pages=24–34|doi= 10.1109/64.511774}}</ref>

Individuals can also take preparedness steps like securing [[water heating|water heaters]] and heavy items that could injure someone, locating shutoffs for utilities, and being educated about what to do when the shaking starts. For areas near large bodies of water, earthquake preparedness encompasses the possibility of a tsunami caused by a large earthquake.

==In culture==

[[File:Lycosthène.jpg|thumb|An image from a 1557 book depicting an earthquake in Italy in the 4th century BCE]]

From the lifetime of the Greek philosopher [[Anaxagoras]] in the 5th century BCE to the 14th century CE, earthquakes were usually attributed to "air (vapors) in the cavities of the Earth."<ref name=World>{{cite encyclopedia
|title=Earthquakes
|encyclopedia=Encyclopedia of World Environmental History
|volume=1: A–G
|pages=358–364
|publisher=Routledge
|year=2003 }}</ref> [[Pliny the Elder]] called earthquakes "underground thunderstorms".<ref name=World/> [[Thales]] of Miletus (625–547 BCE) was the only documented person who believed that earthquakes were caused by tension between the earth and water.<ref name=World/>

In [[Norse mythology]], earthquakes were explained as the violent struggle of the god [[Loki]] being punished for the murder of [[Baldr]], god of beauty and light.<ref>{{cite book|last=[[Snorri Sturluson|Sturluson, Snorri]]|title=Prose Edda|year=1220|isbn=978-1-156-78621-5|title-link=Prose Edda|publisher=General Books }}</ref> In [[Greek mythology]], [[Poseidon]] was the cause and god of earthquakes.<ref name="Dimock1990">{{cite book|author=George E. Dimock|title=The Unity of the Odyssey|url=https://books.google.com/books?id=hS1acr-lOeEC&pg=PA179|year=1990|publisher=Univ of Massachusetts Press|isbn=978-0-87023-721-8|page=179}}</ref> In [[Japanese mythology]], [[Namazu]] (鯰) is a giant [[catfish]] who causes earthquakes.<ref>{{Cite encyclopedia|url=http://www.worldhistory.org/Namazu/|title=Namazu|encyclopedia=World History Encyclopedia|access-date=2017-07-23}}</ref> In [[Taiwan]]ese folklore, the [[Tē-gû]] (地牛) is a giant earth [[True buffalo|buffalo]] who causes earthquakes.<ref>{{cite web |url=https://artouch.com/gumeishu/content-144675.html |title=Earthquake Island, Taiwan: The Ground Buffalo Myth, Deities and Earthquakes |work=ARTouch |date=14 June 2024 |access-date=2025-05-05 }}</ref>

In the [[New Testament]], [[Gospel of Matthew|Matthew's Gospel]] refers to earthquakes occurring both after the [[death of Jesus]] ([[Matthew 27:51]], 54) and at his [[Resurrection of Jesus|resurrection]] ([[Matthew 28:2]]).<ref>Allison, D., ''56. Matthew'', in Barton, J. and Muddiman, J. (2001), [https://b-ok.org/dl/946961/8f5f43 The Oxford Bible Commentary] {{Webarchive|url=https://web.archive.org/web/20171122193211/http://b-ok.org/dl/946961/8f5f43 |date=2017-11-22 }}, p. 884</ref>

In modern popular culture, the portrayal of earthquakes is shaped by the memory of great cities laid waste, such as [[Great Hanshin earthquake|Kobe in 1995]] or [[1906 San Francisco earthquake|San Francisco in 1906]].<ref name="Van Riper 60">{{cite book|last=Van Riper|first=A. Bowdoin|title=Science in popular culture: a reference guide|url=https://archive.org/details/sciencepopularcu00ripe|url-access=limited|publisher=[[Greenwood Press]]|location=Westport|year=2002|page=[https://archive.org/details/sciencepopularcu00ripe/page/n77 60]|isbn=978-0-313-31822-1}}</ref> Fictional earthquakes tend to strike suddenly and without warning.<ref name="Van Riper 60" /> For this reason, stories about earthquakes generally begin with the disaster and focus on its immediate aftermath, as in ''Short Walk to Daylight'' (1972), ''[[A Wrinkle in the Skin|The Ragged Edge]]'' (1968) or ''[[Aftershock: Earthquake in New York]]'' (1999).<ref name="Van Riper 60" /> A notable example is Heinrich von Kleist's classic novella, ''[[The Earthquake in Chile]]'', which describes the destruction of Santiago in 1647. [[Haruki Murakami]]'s short fiction collection ''[[After the Quake]]'' depicts the consequences of the Kobe earthquake of 1995.

{{anchor|big one}}The most popular single earthquake in fiction is the hypothetical "Big One" expected of California's [[San Andreas Fault]] someday, as depicted in the novels ''[[Richter 10]]'' (1996), ''[[Goodbye California (novel)|Goodbye California]]'' (1977), ''[[2012 (film)|2012]]'' (2009), and ''[[San Andreas (film)|San Andreas]]'' (2015), among other works.<ref name="Van Riper 60" />

==Outside of Earth==
{{main|Quake (natural phenomenon)}}
Phenomena similar to earthquakes have been observed on other planets (e.g., ''[[marsquake]]s'' on Mars) and on the Moon (e.g., ''[[moonquake]]s'').

==See also==
{{div col}}
* {{annotated link|Alpide belt}}
* {{annotated link|European-Mediterranean Seismological Centre|abbr=EMSC|aka=Centre Sismologique Euro-Méditerranéen|aka_lang=fr|only=explicit}}
* {{annotated link|Helioseismology|space_cat=no}}
* {{annotated link|Injection well}}
* {{annotated link|IRIS Consortium}}
* [[Lists of earthquakes]]
* {{annotated link|Seismological Society of America|abbr=SSA}}
* {{annotated link|Seismotectonics}}
* {{annotated link|Vertical displacement}}
{{div col end}}

==References==
{{Reflist}}

==Sources==
{{Div col|colwidth=30em}}
{{refbegin}}
* {{citation
|last1= Allen |first1= Clarence R.
|date= December 1976
|title= Responsibilities in earthquake prediction
|journal= Bulletin of the Seismological Society of America
|volume= 66 |issue= 6 |pages= 2069–2074
|doi= 10.1785/BSSA0660062069
|bibcode= 1976BuSSA..66.2069A
}}.
* {{Citation
|last1= Bolt
|first1= Bruce A.
|year= 1993
|title= Earthquakes and geological discovery
|publisher= Scientific American Library
|isbn= 978-0-7167-5040-6
|url-access= registration
|url= https://archive.org/details/earthquakesgeolo0000bolt
}}.
* {{Citation
|first1= D.H.
|last1= Chung
|first2= D.L.
|last2= Bernreuter
|date= 1980
|title= Regional Relationships Among Earthquake Magnitude Scales.
|publisher= Office of Scientific and Technical Information (OSTI)
|doi= 10.2172/5073993
|osti= 5073993
|url= https://www.osti.gov/scitech/servlets/purl/5073993/
|access-date= 2017-07-21
|archive-date= 2020-01-22
|archive-url= https://web.archive.org/web/20200122134130/https://www.osti.gov/biblio/5073993/
|url-status= live
|doi-access= free
}}, NUREG/CR-1457.
* Deborah R. Coen. ''The Earthquake Observers: Disaster Science From Lisbon to Richter'' ([[University of Chicago Press]]; 2012) 348 pages; explores both scientific and popular coverage
* {{citation
|last1= Geller
|first1= Robert J.
|first2= David D.
|last2= Jackson
|first3= Yan Y.
|last3= Kagan
|first4= Francesco
|last4= Mulargia
|date= 14 March 1997
|title= Earthquakes Cannot Be Predicted
|journal= Science
|volume= 275
|issue= 5306
|page= 1616
|doi= 10.1126/science.275.5306.1616
|s2cid= 123516228
|url= http://moho.ess.ucla.edu/~kagan/Geller_et_al_1997.pdf
|access-date= 29 December 2016
|archive-date= 12 May 2019
|archive-url= https://web.archive.org/web/20190512161821/http://moho.ess.ucla.edu/~kagan/Geller_et_al_1997.pdf
|url-status= dead
}}.
* {{citation
|author= International Commission on Earthquake Forecasting for Civil Protection
|date= 30 May 2011
|title= Operational Earthquake Forecasting: State of Knowledge and Guidelines for Utilization
|journal= Annals of Geophysics
|volume= 54
|issue= 4
|pages= 315–391
|doi= 10.4401/ag-5350
|s2cid= 129825964
|url= https://gfzpublic.gfz-potsdam.de/pubman/item/item_243738_1/component/file_243737/17246.pdf
|url-status= live
|archive-url= https://web.archive.org/web/20210717180146/https://gfzpublic.gfz-potsdam.de/rest/items/item_243738_1/component/file_243737/content
|archive-date= 17 July 2021
|archive-format= PDF
}}.
* {{citation
|last1= Kanamori |first1= Hiroo
|year= 2003
|title= Earthquake Prediction: An Overview
|journal= International Handbook of Earthquake and Engineering Seismology
|volume= 616 |pages= 1205–1216
|isbn= 978-0-12-440658-2
|doi=10.1016/s0074-6142(03)80186-9
|series= International Geophysics
|bibcode= 2003InGeo..81.1205K
}}.
* {{Citation
|first1= H.O. |last1= Wood
|first2= B. |last2= Gutenberg
|date= 6 September 1935
|title= Earthquake prediction
|journal= Science
|volume= 82 |issue= 2123 |pages= 219–320
|bibcode = 1935Sci....82..219W |doi = 10.1126/science.82.2123.219
|pmid= 17818812
}}.
{{refend}}
{{div col end}}

==Further reading==
{{Library resources box
|by=no
|onlinebooksabout=yes
|about=yes
|label=Earthquakes
|viaf= |lccn= |lcheading=earthquakes |wikititle=
}}
* {{cite book |title=Natural Hazards and Disasters |first1=Donald |last1=Hyndman |first2=David |last2=Hyndman |isbn=978-0-495-31667-1 |publisher=Brooks/Cole: [[Cengage Learning]] |year=2009 |edition=2nd |chapter-url=https://books.google.com/books?id=8jg5oRWHXmcC&pg=PT54 |chapter=Chapter 3: Earthquakes and their causes }}
* {{cite journal | last1=Liu | first1=ChiChing | last2=Linde | first2=Alan T. | last3=Sacks | first3=I. Selwyn | title=Slow earthquakes triggered by typhoons | journal=Nature | volume=459 | issue=7248 | date=2009 | issn=0028-0836 | doi=10.1038/nature08042 | pages=833–836| pmid=19516339 | bibcode=2009Natur.459..833L | s2cid=4424312 }}

==External links==
{{Wikiquote}}
{{commons}}
{{Wikivoyage|Earthquake safety}}
{{wiktionary}}
* [https://earthquake.usgs.gov/ Earthquake Hazards Program] of the U.S. Geological Survey
* [http://www.iris.edu/dms/seismon.htm IRIS Seismic Monitor] – IRIS Consortium

{{Geotechnical engineering|state=collapsed}}
{{Natural disasters}}
{{Authority control}}

[[Category:Earthquakes| ]]
[[Category:Geological hazards]]
[[Category:Lithosphere]]
[[Category:Natural disasters]]
[[Category:Seismology]]

File:Tohoku earthquake - 2011.glb

2025-08-25T16:15:42Z

OpenDEM 1: Uploaded a work by Loïc Norgeot from https://sketchfab.com/3d-models/tohoku-earthquake-2011-bf7bac2c40d7417c8af31b1cce8a8a47 with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{br|1=The Tōhoku earthquake (9.1 magnitude) hit Japan on March 11, 2011 for a duration of 5 minutes, and was followed by a tsunami which claimed the life of close to 16.000 people.

The seismic events shown took place on that same day, between 01h41 and 23h59 (GMT). At 0.5X animation speed, 1 second of animation = 1 hour in real time.

The main earthquake happened at 05h46 (1:80 mark in the animation), and slowing down the animation speed to 0.1X or keeping manual control around this event should allow you to better understand the aftershocks propagation.

Data:

Topography and bathymetry: Etopo1 Global Relief Model
Earthquakes: ANSS Comprehensive Earthquake Catalog
Fault plane: Slab2: A Comprehensive Subduction Zone Geometry Model
Created with python and blender ( and love :) )}}
|date=08.02.2019
|source=https://sketchfab.com/3d-models/tohoku-earthquake-2011-bf7bac2c40d7417c8af31b1cce8a8a47
|author=Loïc Norgeot
|permission=
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Template:Earthquake sidebar

2025-08-25T16:12:30Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Template:Earthquake_sidebar

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Injection well

2025-08-25T16:12:30Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Injection_well

{{Short description|Device that places fluid deep underground}}
[[File:Deep injection well.jpg|thumb|right|Deep injection well for disposal of hazardous, industrial and municipal wastewater; a "Class I" well under USEPA regulations.<ref name="EPA Basicinfo"/>]]
An '''injection well''' is a device that places fluid deep underground into [[porous rock]] formations, such as sandstone or limestone, or into or below the shallow [[soil]] layer. The fluid may be [[water]], [[wastewater]], [[brine]] (salt water), or water mixed with industrial chemical waste.<ref name="EPA Basicinfo">{{cite web |url=https://www.epa.gov/uic/general-information-about-injection-wells |title=General Information About Injection Wells |publisher=U.S. Environmental Protection Agency (EPA) |location= Washington, DC |date=2020-04-20}}</ref>

==Definition ==
The [[U.S. Environmental Protection Agency]] (EPA) defines an injection well as "a bored, drilled, or driven shaft, or a dug hole that is deeper than it is wide, or an improved sinkhole, or a subsurface fluid distribution system". Well construction depends on the injection fluid injected and depth of the injection zone. Deep wells that are designed to inject [[hazardous wastes]] or carbon dioxide deep below the Earth's surface have multiple layers of protective casing and cement, whereas shallow wells injecting non-hazardous fluids into or above drinking water sources are more simply constructed.<ref name="EPA Basicinfo"/>

==Applications==
{{expand section|date=April 2015}}
Injection wells are used for many purposes.

=== Waste disposal ===
Treated wastewater can be injected into the ground between impermeable layers of rocks to avoid polluting surface waters. Injection wells are usually constructed of solid walled pipe to a deep elevation in order to prevent injectate from mixing with the surrounding environment.<ref name="EPA Basicinfo"/> Injection wells utilize the earth as a filter to treat the wastewater before it reaches the aquifer. This method of wastewater disposal also serves to spread the injectate over a wide area, further decreasing environmental impacts.{{Citation needed|date=January 2021}}

In the United States, there are about 800 deep injection waste disposal wells used by industries such as chemical manufacturers, petroleum refineries, food producers and municipal wastewater plants.<ref>{{cite web |title=Class I Industrial and Municipal Waste Disposal Wells |url=https://www.epa.gov/uic/class-i-industrial-and-municipal-waste-disposal-wells |date=2016-09-06 |website=Underground Injection Control |publisher=EPA}}</ref> Most produced water generated by oil and gas extraction wells in the US is also disposed in deep injection wells.<ref>{{cite report |title=Summary of Input on Oil and Gas Extraction Wastewater Management Practices Under the Clean Water Act |url=https://www.epa.gov/eg/summary-input-oil-and-gas-extraction-wastewater-management-practices-under-clean-water-act-final |archive-url=https://web.archive.org/web/20201016204448/https://www.epa.gov/eg/summary-input-oil-and-gas-extraction-wastewater-management-practices-under-clean-water-act-final |url-status=dead |archive-date=October 16, 2020 |date=May 2020 |publisher=EPA |id=EPA 821-S-19-001 |page=2}}</ref>

Critics of wastewater injection wells cite concerns about potential groundwater contamination. It is argued that the impacts of some injected wastes in groundwater is not fully understood, and that the science and regulatory agencies have not kept up with the rapid expansion of disposal practices in US, where there are over 680,000 wells as of 2012.<ref name="ProPublica-Poison-Beneath">{{cite news |last=Lustgarten |first=Abrahm |title=Injection Wells: The Poison Beneath Us |url=https://www.propublica.org/article/injection-wells-the-poison-beneath-us |date=2012-06-21 |work=ProPublica |location=New York}}</ref>

Alternatives to injection wells include direct discharge of treated wastewater to receiving waters, conditioning of oil drilling and fracking [[produced water]] for reuse, utilization of treated water for irrigation or livestock watering, or processing of water at [[industrial wastewater treatment]] plants.<ref name=Erickson>{{Cite magazine |last=Erickson |first=Britt E. |title=Wastewater from fracking: Growing disposal challenge or untapped resource? |url=https://cen.acs.org/environment/water/Wastewater-fracking-Growing-disposal-challenge/97/i45 |date=2019-11-17 |magazine=Chemical & Engineering News |volume=97 |issue=45}}</ref> Direct discharge does not disperse the water over a wide area; the environmental impact is focused on a particular segment of a river and its downstream reaches or on a coastal water body. Extensive irrigation is not typical in areas where the produced water tends to be salty,<ref name=Erickson /> and this practice is often prohibitively expensive and requires ongoing maintenance and large electricity usage.<ref>{{cite journal |author1=Martin, DL |author2=Dorn, TW |author3=Melvin, SR |author4=Corr, AJ |author5=Kranz, WL |title=Evaluation Energy Use for Pumping Irrigation Water |url=https://www.ksre.k-state.edu/irrigate/oow/p11/Kranz11a.pdf |journal=Proceedings of the 23rd Annual Central Plains Irrigation Conference |location=Burlington, CO |date=February 2011}}</ref>

Since the early 1990s, [[Maui County]], Hawaii has been engaged in a struggle over the 3 to 5 million gallons per day of wastewater that it injects below the [[Lahaina]] Wastewater Reclamation Facility, over the claim that the water was emerging in seeps that were causing [[algae bloom]]s and other environmental damage. After some twenty years, it was sued by environmental groups after multiple studies showed that more than half the injectate was appearing in nearby coastal waters. The judge in the suit rejected the County's arguments, potentially subjecting it to millions of dollars in federal fines. A 2001 consent decree required the county to obtain a water quality certification from the [[Hawaii Department of Health]], which it failed to do until 2010, after the suit was filed.<ref>{{cite web|url=http://www.civilbeat.com/2014/07/federal-judge-rejects-maui-county-arguments-on-lahaina-plant-violations/#comments |title=Federal Judge Rejects Maui County Arguments on Lahaina Plant Violations |date=9 July 2014 |publisher=Civil Beat |access-date=2014-07-22}}</ref> The case proceeded through the [[United States Court of Appeals for the Ninth Circuit]] and subsequently to the [[Supreme Court of the United States]]. In 2020 the Court ruled in ''[[County of Maui v. Hawaii Wildlife Fund]]'' that injection wells may be the "functional equivalent of a direct discharge" under the Clean Water Act, and instructed the EPA to work with the courts to establish regulations when these types of wells should require permits.<ref>{{cite web |url=https://www.bloomberg.com/news/articles/2020-04-23/supreme-court-issues-mixed-ruling-on-reach-of-clean-water-act |title=Supreme Court Gives Environmentalists Partial Win on Water Law |first=Greg |last=Stohr |date=April 23, 2020 |work=Bloomberg News}}</ref>

===Oil and gas production===
{{see|Enhanced oil recovery|Hydraulic fracturing}}
Another use of injection wells is in [[natural gas]] and [[petroleum]] [[Extraction of petroleum|production]]. Steam, [[carbon dioxide]], water, and other substances can be [[water injection (oil production)|injected into an oil-producing unit]] in order to maintain [[petroleum reservoir|reservoir]] pressure, heat the oil or lower its viscosity, allowing it to flow to a producing well nearby.<ref name="EPA Class II">EPA. [https://www.epa.gov/uic/class-ii-oil-and-gas-related-injection-wells "Class II Oil and Gas Related Injection Wells."] Updated 2015-10-08.</ref>

===Waste site remediation===
Yet another use for injection wells is in [[environmental remediation]], for cleanup of either [[soil contamination|soil]] or [[groundwater contamination]]. Injection wells can insert clean water into an [[aquifer]], thereby changing the direction and speed of groundwater flow, perhaps towards [[extraction well]]s downgradient, which could then more speedily and efficiently remove the contaminated groundwater. Injection wells can also be used in cleanup of soil contamination, for example by use of an ozonation system. Complex [[hydrocarbons]] and other contaminants trapped in soil and otherwise inaccessible can be broken down by [[ozone]], a highly reactive gas, often with greater cost-effectiveness than could be had by digging out the affected area. Such systems are particularly useful in built-up urban environments where digging may be impractical due to overlying buildings.<ref>EPA. New York, NY (2003-04-17). [https://web.archive.org/web/20110609041407/http://yosemite.epa.gov/opa/admpress.nsf/6427a6b7538955c585257359003f0230/7bfcdcd6fef70da285257163005c159c!OpenDocument "EPA Announces Cleanup Plan for Contaminated Soil and Ground Water at Central Islip Superfund Site."] Example of use of ozonation wells for remediation ''in situ.''</ref>

===Aquifer recharge===
Recently the option of [[Groundwater recharge|refilling natural aquifers]] with injection or percolation has become more important, particularly in the driest region of the world, the [[MENA]] region (Middle East and North Africa).<ref>H2O magazine (2010-10-16). [http://www.h2ome.net/en/2010/10/strategic-reserve/ "Strategic reserve"] by Anoop K Menon</ref>

[[Surface runoff]] can also be recharged into [[dry well]]s, or simply barren wells that have been modified to functions as cisterns.<ref>H2O magazine (2011-05-03). [https://prototype-creation.de/recharging_dry_wells.pdf/ "Recharging dry wells."] {{Webarchive|url=https://web.archive.org/web/20200708123930/http://www.prototype-creation.de/recharging_dry_wells.pdf |date=2020-07-08 }} by Nicol-André Berdellé</ref> These hybrid [[stormwater]] management systems, called [[recharge well]]s, have the advantage of aquifer recharge and instantaneous supply of potable water at the same time. They can utilize existing infrastructure and require very little effort for the modification and operation. The activation can be as simple as inserting a polymer cover (foil) into the well shaft. Vertical pipes for conduction of the overflow to the bottom can enhance performance. The area around the well acts as funnel. If this area is maintained well the water will require little purification before it enters the cistern.<ref>Prototype-Creation (2011-04-20). [http://www.prototype-creation.de/recharge_wells.pdf "Recharge wells and ASR."] by Nicol-André Berdellé</ref>

===Geothermal energy===
Injection wells are used to tap [[geothermal energy]] in hot, porous rock formations below the surface by injecting fluids into the ground, which is heated in the ground, then extracted from adjacent wells as fluid, steam, or a combination of both. The heated steam and fluid can then be utilized [[geothermal power|to generate electricity]] or directly for [[geothermal heating]].<ref name="EERE pamphlet">{{cite web |title=Geothermal Technologies Program: Tapping the Earth's energy to meet our heat and power needs |url=https://www.nrel.gov/docs/fy04osti/36025.pdf |publisher=U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy |access-date=2 June 2018 |date=April 2004}}</ref><ref name="Fitch and Matlick 2008">{{cite journal |last1=Fitch |first1=David |last2=Matlick |first2=Skip |title=Gold, silver and Other Metals in scale— Puna Geothermal Venture, Hawaii |journal=GRC Transactions |date=2008 |volume=32 |pages=385–388 |url=http://pubs.geothermal-library.org/lib/grc/1028353.pdf |access-date=2 June 2018 |archive-date=1 November 2016 |archive-url=https://web.archive.org/web/20161101002822/http://pubs.geothermal-library.org/lib/grc/1028353.pdf |url-status=dead }}</ref><ref name="Direct uses">{{cite web |last1=Gill |first1=Andrea T. |title=Prospective Direct Use Enterprises in Kapoho, Hawaii |url=https://energy.hawaii.gov/wp-content/uploads/2011/10/Prospective-Direct-Use-Enterprises-in-Kapoho-Hawaii.pdf |publisher=Hawaii Dept. of Business, Economic Development and Tourism, Strategic Industries Division |access-date=2 June 2018 |date=2004}}</ref>

==Regulatory requirements==
In the United States, injection well activity is regulated by EPA and state governments under the [[Safe Drinking Water Act]] (SDWA).<ref name="EPA Basicinfo"/> The “State primary enforcement responsibility” section of the SDWA provides for States to submit their proposed UIC program to the EPA to request State assumption of primary enforcement responsibility. <ref>{{USC|42|300h-1}}(b)</ref> Thirty-four states have been granted UIC primacy enforcement authority for Class I, II, III, IV and V wells.<ref name="EPA-UIC-primacy">{{cite web |url=https://www.epa.gov/uic/primary-enforcement-authority-underground-injection-control-program |archive-url=https://web.archive.org/web/20151013162417/http://www2.epa.gov/uic/primary-enforcement-authority-underground-injection-control-program |url-status=dead |archive-date=October 13, 2015 |title=Primary Enforcement Authority for the Underground Injection Control Program |author= |date=2019-04-15 |publisher=EPA}}</ref> For states without an approved UIC program, the EPA administrator prescribes a program to apply.<ref>{{USC|42|300h-1}}(c)</ref> EPA has issued Underground Injection Control (UIC) regulations in order to protect drinking water sources.<ref name="EPA Regs">EPA. [https://www.epa.gov/uic/underground-injection-control-regulations "Underground Injection Control Regulations."] Updated 2015-10-05.</ref><ref>EPA. (July 2001). [https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=2000E99H.PDF "Technical Program Overview: Underground Injection Control Regulations."] Document no. EPA 816-R-02-025.</ref>

EPA regulations define six classes of injection wells. Class I wells are used for the injection of municipal and industrial wastes beneath underground sources of drinking water. Class II wells are used for the injection of fluids associated with oil and gas production, including waste from hydraulic fracturing. Class III wells are used for the injection of fluids used in mineral [[solution mining]] beneath underground sources of drinking water. Class IV wells, like Class I wells, were used for the injection of hazardous wastes but inject waste into or above underground sources of drinking water instead of below. EPA banned the use of Class IV wells in 1984.<ref>{{cite web |url=https://www.epa.gov/uic/class-iv-shallow-hazardous-and-radioactive-injection-wells |title=Class IV Shallow Hazardous and Radioactive Injection Wells |author= |date=2016-09-06 |website=Underground Injection Control |publisher=EPA}}</ref> Class V wells are those used for all non-hazardous injections that are not covered by Classes I through IV. Examples of Class V wells include stormwater drainage wells and [[Septic drain field|septic system leach fields]]. Finally, Class VI wells are used for the injection of carbon dioxide for [[Carbon sequestration|sequestration]], or long term storage.<ref name="EPA Basicinfo"/> Since the introduction of Class VI in 2010, only two Class VI wells have been constructed as of 2022, both at the same Illinois facility; four other approved projects did not proceed to construction. <ref>{{cite web|url=https://www.mayerbrown.com/en/insights/publications/2022/06/carbon-capture-utilization-and-storage-class-vi-wells-and-us-state-primacy|title="CARBON CAPTURE, UTILIZATION, AND STORAGE: CLASS VI WELLS AND US STATE PRIMACY"|author=
Philip K. Lau and Nadav C. Klugman|date=2022-06-22}}</ref>

==Injection-induced earthquakes==
[[File:Cumulative induced seismicity.png|thumbnail|Cumulative number of earthquakes in the central U.S. The red cluster at the center of the map shows an area near Oklahoma which experienced the largest increase in activity since 2009.]]
{{see also|Induced seismicity#Waste_disposal_wells|label 1=Induced seismicity § Waste disposal wells}}
A July 2013 study by US Geological Survey scientist William Ellsworth links earthquakes to wastewater injection sites. In the four years from 2010-2013 the number of earthquakes of magnitude 3.0 or greater in the central and eastern United States increased dramatically. After decades of a steady earthquake rate (average of 21 events/year), activity increased starting in 2001 and peaked at 188 earthquakes in 2011, including [[2011 Oklahoma earthquake|a record-breaking 5.7-magnitude earthquake]] near [[Prague, Oklahoma]] which was the strongest earthquake ever recorded in Oklahoma. USGS scientists have found that at some locations the increase in seismicity coincides with the injection of wastewater in deep disposal wells. Injection-induced earthquakes are thought to be caused by pressure changes due to excess fluid injected deep below the surface and are being dubbed “man-made” earthquakes.<ref name="Man-Made Earthquakes Update">USGS. [http://www.usgs.gov/blogs/features/usgs_top_story/man-made-earthquakes/ "Man-Made Earthquakes Update"] {{Webarchive|url=https://web.archive.org/web/20140329224145/http://www.usgs.gov/blogs/features/usgs_top_story/man-made-earthquakes/ |date=2014-03-29 }} Updated January 17, 2014.</ref> On September 3, 2016, [[2016 Oklahoma earthquake|a 5.8-magnitude earthquake]] occurred near [[Pawnee, Oklahoma]], followed by nine aftershocks between magnitudes 2.6 and 3.6 within three and one-half hours. The earthquake broke the previous record set five years earlier. Tremors were felt as far away as [[Memphis, Tennessee]], and [[Gilbert, Arizona]]. [[Mary Fallin]], the Oklahoma governor, declared a local emergency and shutdown orders for local disposal wells were ordered by the Oklahoma Corporation Commission.<ref>[http://hosted.ap.org/dynamic/stories/U/US_MIDWEST_EARTHQUAKE Record tying Oklahoma earthquake felt as far away as Arizona], ''[[Associated Press]]'', Ken Miller, September 3, 2016. Retrieved 4 September 2016.</ref><ref>[http://www.enidnews.com/news/updated-with-fallin-comments-aftershocks-large-and-long-earthquake-felt/article_184f9e1e-71d2-11e6-8dc9-87f17af9538d.html USGS calls for shut down of wells, governor declares emergency in wake of 5.6 quake in Oklahoma], ''[[Enid News & Eagle]]'', Sally Asher & Violet Hassler, September 3, 2016. Retrieved 4 September 2016.</ref> Results of ongoing multi-year research on induced earthquakes by the [[United States Geological Survey]] (USGS) published in 2015 suggested that most of the significant earthquakes in Oklahoma, such as the 1952 magnitude 5.5 El Reno earthquake may have been induced by deep injection of waste water by the oil industry.<ref name="usgs_2015">{{cite web |url=http://www.usgs.gov/newsroom/article.asp?ID=4362#.Vj-sOpTIxku |title=A Century of Induced Earthquakes in Oklahoma? |last1=Hough |first1=Susan E. |last2=Page |first2=Morgan |date=October 20, 2015 |publisher=U.S. Geological Survey |access-date=November 8, 2015 |quote=Several lines of evidence further suggest that most of the significant earthquakes in Oklahoma during the 20th century may also have been induced by oil production activities. Deep injection of waste water, now recognized to potentially induce earthquakes, in fact began in the state in the 1930s.}}</ref>

==Notes==
{{Reflist}}

==References==
{{refbegin}}
* US Army Environmental Center. Aberdeen Proving Ground, MD (2002). [http://www.frtr.gov/matrix2/section4/4-54.html "Deep Well Injection."] ''Remediation Technologies Screening Matrix and Reference Guide.'' 4th ed. Report no. SFIM-AEC-ET-CR-97053.
{{refend}}

==External links==
{{Commons category|Injection wells}}
*[https://www.epa.gov/uic EPA - Underground Injection Control Program]

{{Wastewater}}

{{DEFAULTSORT:Injection Well}}
[[Category:Drinking water]]
[[Category:Hydrology]]
[[Category:Natural gas technology]]
[[Category:Petroleum technology]]
[[Category:Water pollution]]
[[Category:Oil wells]]
[[Category:Water wells]]

Alpide belt

2025-08-25T16:12:29Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Alpide_belt

{{Short description|Belt of Eurasian mountain ranges}}
{{Redirect-distinguish|Alpide|Alpine (disambiguation){{!}}Alpine}}
{{Infobox mountain
| name =
| other_name = Alpine-Himalayan orogenic belt
| photo = File:Alpiner Gebirgsgürtel.png
| photo_size = 300px
| photo_alt =
| photo_caption = Approximate extent of the Alpide orogenic system


| highest = [[Mount Everest]]
| highest_location =
| elevation =
| elevation_m = 8848.86
| elevation_ft =
| elevation_ref =
| elevation_system =
| prominence =
| prominence_m =
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| parent_peak =
| isolation =
| isolation_m =
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| isolation_ref =
| isolation_parent =
| listing =
| coordinates =
| coordinates_ref =

| length =
| length_km = 15,000
| length_mi =
| length_orientation = E–W in the west, N–S in the east
| length_ref =
| width =
| width_km =
| width_mi =
| width_orientation =
| width_ref =
| area =
| area_km2 =
| area_mi2 =
| area_ref =
| volume =
| volume_km3 =
| volume_mi3 =
| volume_ref =

| etymology = Derived from ''Alps''
| nickname =
| native_name =
| native_name_lang =
| translation =
| pronunciation =
| authority =

| country =
| country_type =
| state =
| state_type =
| location =
| region =Southern Eurasia, northern Africa, central Asian subcontinent, southeast Asia
| region_type =Mesozoic oceanic platform
| district =
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| grid_ref_UK_ref =
| grid_ref_Ireland =
| grid_ref_Ireland_ref =
| topo_maker =
| topo_map =
| biome =

| formed_by = compressive forces at aligned convergent plate boundaries
| orogeny = [[Alpine orogeny|Alpine]] (in west), [[Geology of the Himalayas|Himalayan]] (in east)
| age =
| type = Folded mountain ranges
| geology =
| volcanic_region =
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| first_ascent =
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}}

The '''Alpide belt''' or '''Alpine-Himalayan orogenic belt''',<ref name=Storetvedt>K.M. Storetvedt, K. M., ''The Tethys Sea and the Alpine-Himalayan orogenic belt; mega-elements in a new global tectonic system,'' Physics of the Earth and Planetary Interiors, Volume 62, Issues 1–2, 1990, Pages 141–184 [http://www.sciencedirect.com/science/article/pii/0031920190901987 Abstract]</ref> or more recently and rarely '''the Tethyan orogenic belt''', is a [[earthquake|seismic]] and [[orogeny|orogenic]] belt that includes an array of [[mountain range]]s extending for more than {{convert|15000|km|mi}} along the southern margin of [[Eurasia]], stretching from [[Java]] and [[Sumatra]], through the [[Indochinese Peninsula]], the [[Himalayas]] and [[Transhimalaya]]s, the [[List of mountains in Iran|mountains of Iran]], [[Caucasus]], [[Anatolia]], the [[Mediterranean]], and out into the [[Atlantic]].<ref name="USGS1"/>

It includes, from west to east, the major ranges of the [[Atlas Mountains]], the [[Alps]], the [[Caucasus Mountains]], [[Alborz]], [[Hindu Kush]], [[Karakoram]], and the [[Himalayas]]. It is the second most seismically active region in the world, after the circum-Pacific belt (the [[Ring of Fire]]), with 17% of the world's largest earthquakes.<ref name="USGS1">{{cite web |url=http://www.usgs.gov/faq/categories/9831/3342 |title=Where do earthquakes occur? |publisher=United States Geological Survey |access-date=8 March 2015 |url-status=dead |archive-url=https://web.archive.org/web/20140805134145/http://www.usgs.gov/faq/categories/9831/3342 |archive-date=5 August 2014 }}</ref>

The belt is the result of [[Mesozoic]]-to-[[Cenozoic]]-to-recent closure of the [[Tethys Ocean]] and process of collision between the northward-moving [[African plate|African]], [[Arabian plate|Arabian]], and [[Indian plate]]s with the [[Eurasian plate]].<ref name=Storetvedt/> Each collision results in a [[convergent boundary]], a topic covered in [[plate tectonics]]. The approximate alignment of so many convergent boundaries trending east to west, first noticed by the Austrian geologist [[Eduard Suess]], suggests that {{citation needed span|date=March 2024|once many plates were one plate, and the collision formed one subduction zone, which was oceanic, subducting the floor of Tethys.}}

Suess called the single continent [[Gondwana]], after some rock formations in India, then part of the supercontinent of Gondwana, which had earlier divided from another supercontinent, [[Laurasia]], and was now pushing its way back. Eurasia descends from Laurasia, the Laurentia part having split away to the west as a consequence of the formation of the North Atlantic Ocean. As Tethys closed, Gondwana pushed up mountain ranges on the southern margin of Eurasia.

==Brief history of the concept==
The Alpide belt is a concept from modern [[historical geology]], the study in geologic time of the events that shaped the surface of the Earth.<ref>{{harvnb|Suess|1904|p=594}} "In human affairs as in the physical world the present is only a transverse section; we cannot see the future which lies beyond, but we may gain instruction from the past. Thus the history of the earth is of fundamental importance in the description of the earth."</ref> The topic began suddenly in the mid-19th century with the evolutionary biologists. The early historical geologists, such as [[Charles Darwin]] and [[Charles Lyell]], arranged fossils and layers of sedimentary rock containing them into time periods, of which the framework remains.<ref name="Suess 1904 594">{{harvnb|Suess|1904|p=594}} "A general comparative orography, drawn from the existing store of observations, has not yet been created, and he who endeavours step by step to organize the elements of such a synthesis must be content if he finds that the structure he has raised is open to completion and correction,..."</ref>

The late 19th century was a period of synthesis, in which geologists attempted to combine all the detail into the big picture. The first of his type, [[Eduard Suess]], used the term "comparative orography" to refer to his method of comparing mountain ranges, parallel to "comparative anatomy" and "comparative philology.<ref name="Suess 1904 594"/>

His work preceded plate tectonics and continental drift. This pre-tectonic phase lasted until about 1950, when the drift theory won the field just as suddenly as had the evolutionist. The concepts and language of the comparative graphists were kept with some modification, but were explained in new ways.

===Suess's subsidence theory===
The author of the concept of a trans-Eurasian zone of [[subsidence]], which he called [[Tethys Ocean|Tethys]], was [[Eduard Suess]]. He knew it had been a subsidence because it expressed deposits of the [[Mesozoic]], now indurated into layers and raised into highlands by compressional force.<ref>{{harvnb|Suess|1908|p=19}} "Gondwana-land is bounded on the north by a broad zone of marine deposits of Mesozoic age....It must be regarded in its entirety as the relic of a sea which once extended across the existing continent of Asia."</ref> Suess had discovered the zone during his early work on the [[Alps]]. He spent the better part of his career following the zone in detail, which he assembled in one ongoing work, ''das Antlitz der Erde'', "The Face of the Earth." Like a human face, the Earth's face has [[lineament]]s. Suess's topic was the definition and classification of the lineaments of this zone, which he traced from one end of Eurasia to the other, ending on the east with the [[Malay Peninsula]].

Suess looked, as did all geologists, at the strata and content of [[sedimentary rock]], deposited as sediment in the oceanic basins, indurated under the pressure of the depths, and raised later under horizontal pressure into folds of mountain chains. What he added to the field is the study of what he called the "trend-lines" or directions of mountains chains. These were to be discovered by examining their [[Strike and dip|strikes]], or intersections with the surface. He soon discovered what are known today as convergent plate borders, which are chains of mountains raised by the compression or subduction of one plate under another, but knowledge was not in such a state that he could recognize them as that. He concerned himself instead with the patterns.


==Main ranges (from west to east)==
* [[Cantabrian Mountains]] (incl. the [[Basque Mountains]]), [[Sistema Central]], [[Sistema Ibérico]], [[Pyrenees]], [[Alps]], [[Carpathian Mountains|Carpathians]], [[Balkan Mountains]] (Balkanides), [[Rila]]-[[Rhodope Mountains|Rhodope]] [[massif]]s, [[Thracian Sea]] [[Thasos|islands]], [[Crimean Mountains]] – entirely in [[Europe]]
* [[Atlas Mountains|Atlas]] and [[Rif]] Mountains in [[Northern Africa]], [[Baetic System]] ([[Sierra Nevada (Spain)|Sierra Nevada]] and [[Balearic Islands]]), [[Apennine Mountains]], [[Dinaric Alps]], [[Pindus]] (Hellenides), and [[Mount Ida (Crete)|Mount Ida]];
* [[Caucasus Mountains]] (on the [[Boundaries between the continents of Earth|limits between Asia and Europe]]), [[Kopet Dag|Kopet Mountains]], [[Pamir Mountains|Pamir]], [[Pamir-Alay|Alay]] Mountains, [[Tian Shan]], [[Altai Mountains]], [[Sayan Mountains]];
* [[Pontic Mountains]], [[Armenian highlands]], [[Alborz]], [[Hindu Kush]], [[Kunlun Mountains]], [[Hengduan Mountains]], [[Annamite Range]], [[Titiwangsa Mountains]], [[Barisan Mountains]] – entirely in [[Asia]];
* [[Taurus Mountains]], [[Troodos Mountains]], [[Zagros Mountains]], [[Makran]] Highland, [[Sulaiman Mountains]], [[Karakoram]], [[Himalayas]], [[Transhimalaya]], [[Patkai]], [[Chin Hills]], [[Arakan Mountains]], [[Andaman Islands|Andaman]] and [[Nicobar Islands]] – entirely in [[Asia]].

[[Indonesia]] lies between the Pacific [[Ring of Fire]] along the northeastern islands adjacent to and including [[New Guinea]] and the Alpide belt along the south and west from [[Sumatra]], [[Java]] and the [[Lesser Sunda Islands]] ([[Bali]], [[Flores]], and [[Timor]]). The [[2004 Indian Ocean earthquake]] just off the coast of Sumatra was located within the Alpide belt.

==Etymology==
The word ''Alpide'' is a term first coined in German by Austrian geologist [[Eduard Suess]] in his 1883 magnum opus ''Das Antlitz der Erde''<ref name="suess1909">{{cite book|last1=Suess|first1=Eduard|author-link1=Eduard Suess|title=Das Antlitz der Erde|trans-title=The Face of the Earth|language=de|publication-date=1909|orig-date=1883|volume=3.2, part 4|chapter=10: Eintritt der Altaiden nach Europa|page=3|publisher=F. Tempsky|publication-place=Vienna|url=https://archive.org/details/dasantlitzdererdv3p2sues/page/n12/mode/1up|access-date=2023-12-30|lccn=10004406|oclc=1414429730|quote=Die zweite Aenderung besteht darin, dass nun die Ketten, welche jünger sind als das Ober-Carbon oder Perm, sich räumlich scharf abtrennen. Sie liegen fast ganz innerhalb von Senkungen der Altaiden, umrahmt von Linien, die nicht selten das Streichen der Altaiden durchschneiden. Man kann diese umrahmten Ketten als posthume Altaiden ansehen. Die alpinen Ketten (''Alpiden'') sind ihr wichtigstes Glied. Die ''Alpiden'' besitzen einen tertiären Saum. Im variscischen Aussenrande, z. B. ausserhalb der belgischen Kohlenfelder, sieht man nichts Aehnliches. Ueberhaupt ist jüngere Faltung in den Horsten der europäischen Altaiden nur gar selten und in geringem Maasse sichtbar. Es ist, als wäre der Rahmen erstarrt, und die Faltung vom Ober-Carbon an auf die gesenkten Räume eingeschränkt.|trans-quote=In the next place those chains of the Altaides which are younger than the upper Carboniferous and the Permian are separated sharply in space. They lie almost wholly within subsided areas of the Altaides, framed in by lines which frequently cut across the strike of these mountains. We may regard the chains thus framed in as posthumous Altaides. The Alpine chains (''Alpides'') are their most important member. The ''Alpides'' are bordered by a Tertiary zone. Nothing analogous to this is to be seen in the outer margin of the Variscan arc, i.e. outside the Belgian coal-fields. Indeed the younger folding occurs but seldom in the horsts of the European Altaides, and is then only feebly developed. It is as though the frame had become rigid, and the folding, from the upper Carboniferous onwards, had been confined to the downthrown areas. (translated by Hertha B. C. Sollas, under the direction of W. C. Sollas, 1909)}}</ref> and later popularized in English-language scientific literature by Turkish geologist and historian [[Celâl Şengör|A. M. Celâl Şengör]] in a 1984 paper on the topic.<ref name="sengor1984">{{cite book|last1=Şengör|first1=A. M. Celâl|author-link1=Celâl Şengör|title=The Cimmeride Orogenic System and the Tectonics of Eurasia|url=https://books.google.com/books?id=p2cB30_SniMC&pg=PA11|volume=195|series=Geological Society of America Special Paper|page=11|year=1984|url-access=limited|access-date=2023-12-30|publisher=[[Geological Society of America]]|publication-place=Boulder, CO|doi=10.1130/SPE195|isbn=9780813721958|lccn=84018845|oclc=859566590|quote=Figure 7 shows the present extent of the orogenic system related to the obliteration of Paleo-Tethys as compared with that generated during the closure of Neo-Tethys. I call the former the Cimmerides (Figure 7B, I); the latter I define to constitute the ''Alpides'' (Figure 7B, II). The Cimmerides and the ''Alpides'' may be defined to form the Tethysides, for they both descended from Tethys s.l. (Figure 7A). The Alpine-Himalayan mountain belt therefore consists of two mutually independent, but largely superimposed orogenic complexes (Figure 7A).}}</ref> The term adds the suffix ''-ides'', derived from the Ancient Greek patronymic/familial suffix {{lang|grc|-ίδης}} ({{transliteration|grc|-ídēs}}), to the ''Alps'', suggesting a "family" of related orogens. The term ''belt'' refers to the fact that the Alpides form a long, mostly unbroken chain of orogens running west to east along the southern edge of Eurasia.

==Orogeny==
If "Alpide" is taken in Kober's sense to mean the last and current of a collective group of contemporaneous ridges over the entire Tethyan region, then "Alpine orogeny" is used collectively of all the orogenies required to create the Alpides, a definition that is far from the original meanings of Alpide and Alpine, representing a specialized geologic usage.

==See also==
*{{annotated link|Geology of the Alps}}
*[[Alpine orogeny]] -- Formation of the Alpide belt

== Citations ==
{{Reflist}}

== General and cited references ==
* {{Cite book |last=Suess |first=Eduard |year=1904 |editor-first=W. J. |editor-last=Sollas |translator-first=Hertha B. C. |translator-last=Sollas |title=The Face of the Earth |trans-title=das Antlitz der Erde |url=https://archive.org/details/in.ernet.dli.2015.42506/page/n5/mode/1up?q=comparative |volume=I |location=Oxford |publisher=Clarendon Press}}
* {{Cite book |last=Suess |first=Eduard |year=1908 |editor-first=W. J. |editor-last=Sollas |translator-first=Hertha B. C. |translator-last=Sollas |title=The Face of the Earth |trans-title=das Antlitz der Erde|url=https://archive.org/details/in.ernet.dli.2015.22197/page/n28/mode/1up |edition=Revised |volume=III |location=Oxford |publisher=Clarendon Press}}

==External links==
{{commons category}}
* [https://web.archive.org/web/20060117041632/http://earthquake.usgs.gov/faq/hist.html Historic Earthquakes & Earthquake Statistics – USGS]
* [http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/description_plate_tectonics.html "Ring of Fire", Plate Tectonics, Sea-Floor Spreading, Subduction Zones, "Hot Spots" – USGS]

[[Category:Geographic areas of seismological interest]]
[[Category:Plate tectonics]]
[[Category:Volcanism]]
[[Category:Belt regions]]

Vertical displacement

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OpenDEM 1: 1 revision imported from :wikipedia:en:Vertical_displacement

{{Short description|Vertical shift of land in plate tectonics}}
{{about|the concept in geosciences|the concept in mathematics|Vertical translation|the concept in physics|Vertical separation}}

In [[tectonics]], '''vertical displacement''' refers to the shifting of land in a [[vertical direction]], resulting in [[Tectonic uplift|uplift]] and [[subsidence]].<ref name=":3" /> The [[Stratigraphy|displacement of rock layers]] can provide information on how and why Earth's lithosphere changes throughout geologic time.<ref name=":3">{{Cite book|title=Tectonic Geomorphology|last=Anderson, Burbank|first=R.W., D.W.|publisher=Wiley-Blackwell|year=2011|isbn=9781444345032|location=Oxford, UK, Chichester, UK, Hoboken, NJ|pages=viii-x}}</ref> There are different mechanisms which lead to vertical displacement such as tectonic activity, and isostatic adjustments. Tectonic activity leads to vertical displacement when crust is rearranged during a [[Seismology|seismic]] event. Isostatic adjustments result in vertical displacement through sinking due to an increased load or [[isostatic rebound]] due to load removal.

== Tectonic causes of vertical displacement ==
[[File:Small thrust South verging.jpg|thumb|Displacement of the dark mudstone layer pictured is a part of the surface layer above (not pictured), indicating a vertical displacement of this layer of rock.]]Vertical displacement resulting from tectonic activity occurs at [[Divergent boundary|divergent]] and [[Convergent boundary|convergent plate boundaries]]. The movement of magma in the [[asthenosphere]] can create divergent plate boundaries as the magma begins to rise and protrude weaker [[Lithosphere|lithospheric crust]]. Subsidence at a divergent plate boundary is a form of vertical displacement which occurs when a plate begins to split apart.<ref name=":1">{{Cite journal|last1=Trippanera|first1=D.|last2=Acocella|first2=V.|last3=Ruch|first3=J.|date=2014|title=Dike-induced contraction along oceanic and continental divergent plate boundaries|journal=Geophysical Research Letters|language=en|volume=41|issue=20|pages=7098–7104|doi=10.1002/2014GL061570|issn=1944-8007|bibcode=2014GeoRL..41.7098T|hdl=10754/347007|s2cid=53476061 |hdl-access=free}}</ref> As intrusive magma widens the [[Rift|rift zone]] of a divergent plate boundary the layers of crust on the surface above the rift will subside into the rift, creating a vertical displacement of those layers of surface crust.<ref name=":1" />

Convergent plate boundaries create orogenies such as the [[Laramide orogeny]] that raised the Rocky Mountains.<ref name=":2">{{Cite book|title=Roadside Geology of Wyoming|last=Lageson, D.R., and Spearing D.R.|publisher=Mountain Press Publishing Company|year=1998|isbn=978-0-87842-216-6|location=Missoula|pages=15, 23-31, 47-49, 209-217}}</ref> For this orogen event dense oceanic crust from the Pacific plate subducts beneath the less dense continental crust of the North American plate as they converge. This subduction induced the compression of the bounded western region of the North American plate which created the uplift of different layers of rock. This vertical displacement created the various mountain formations which are cumulatively known as the [[Rocky Mountains|Rocky Mountain range]].<ref name=":2" />

[[Earthquake|Earthquakes]] are one mechanism that leads to vertical displacement of crust. The fracturing of land during an earthquake creates a [[Fault (geology)|fault]] when land is displaced during the event.<ref>Rafferty, John P., (2013). "Geological Sciences". New York, NY: Rosen Publishing Group. 9781615305445. https://www.vitalsource.com/sa/en-us/products/geological-sciences-britannica-educational-v9781615305445</ref> The throw of the fault is a term used to describe and quantify the magnitude of this displacement.

== Glacial isostatic adjustment ==
{{main|Glacial isostatic adjustment}}
[[File:Glacier_weight_effects_LMB_(no_text).png|thumb|261x261px|top: Image shows isostatic depression due to the weight of ice on top of it. bottom: Image shows isostatic rebound due to load removal.]]

Changes in [[Glacial period|glaciation]] can lead to the vertical displacement of crust. Glaciers and ice sheets residing on top of landmass result in an [[isostatic depression]], or sinking, in a section of lithospheric crust due to the weight of the ice. Likewise, [[isostatic rebound]], or uplift, occurs when glaciers and ice sheets [[Receding glacier|recede]].<ref name=":0">{{Cite journal|last=Einarsson, Thorleifur, and Norddahl, Hreggvidur|date=2001|title=Concurrent changes of relative sea-level and glacier extent at the Weichselian-Holocene boundary in Berufjordur, Eastern Iceland|journal=Quaternary Science Reviews|volume=20|issue=15|pages=1607–1622|doi=10.1016/S0277-3791(01)00006-3|bibcode=2001QSRv...20.1607N}}</ref>

Using asthenosphere [[viscosity]] data researchers are able to determine the rate by which isostatic rebound occurs. Isostatic rebound occurrence rate can be determined by comparing local viscosities to the maximum viscosity of the asthenosphere. Areas with higher viscosity are subject to quick isostatic rebound while in regions of low viscosity crustal uplift occurs at a slower rate. Uplift is still occurring through isostatic rebound from the [[Last Glacial Maximum]].<ref>{{Cite journal|last=Peltier|first=W. R.|date=1998|title=Postglacial variations in the level of the sea: Implications for climate dynamics and solid-Earth geophysics|journal=Reviews of Geophysics|language=en|volume=36|issue=4|pages=603–689|doi=10.1029/98RG02638|issn=1944-9208|bibcode=1998RvGeo..36..603P|doi-access=}}</ref>

Glacial isostatic rebound leads to sea level regression which can be measured using [[Radiocarbon dating|14C dating]] to determine the age of [[Littoral zone|sublittoral]] sediment in different regions along the seafloor.<ref name=":0" />

== See also ==
* [[Ground displacement]]

== Notes ==
{{reflist}}

[[Category:Plate tectonics]]
[[Category:Vertical position]]

Template:Geotechnical engineering

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OpenDEM 1: 1 revision imported from :wikipedia:en:Template:Geotechnical_engineering

{{Navbox
| name = Geotechnical engineering
| title = [[Geotechnical engineering]]
| state = {{{state|{{{1|}}}}}}
| above = [[Offshore geotechnical engineering]]
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| group1 = [[Geotechnical investigation|Investigation]] and instrumentation
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| group1 = Field (''in situ'')
| list1 =
{{div col|colwidth=33em|content=
* [[File:Core sample.svg|20x20px|class=noviewer]] [[Core drill]]

* [[File:Cone penetration test.svg|20x20px|class=noviewer]] [[Cone penetration test]]

* [[File:Geo-electrical sounding.svg|20x20px|class=noviewer]] [[Geo-electrical sounding]]

* [[File:In situ permeameter test.svg|20x20px|class=noviewer]] [[Permeability (Earth sciences)|Permeability test]]

* [[File:Load test.svg|20x20px|class=noviewer]] [[Load test]]
** [[Static load testing|Static]]
** [[Dynamic load testing|Dynamic]]
** [[Statnamic load test|Statnamic]]

* [[File:Pore pressure measurement.svg|20x20px|class=noviewer]] Pore pressure measurement
**[[Piezometer]]
**[[Well#Classification|Well]]

* [[File:Ram sounding.svg|20x20px|class=noviewer]] [[Ram sounding]]

* [[File:Rock control drilling.svg|20x20px|class=noviewer]] [[Rock control drilling]]

* [[File:Rotary pressure sounding.svg|20x20px|class=noviewer]] [[Rotary-pressure sounding]]

* [[File:Rotary weight sounding.svg|20x20px|class=noviewer]] [[Rotary weight sounding]]

* [[File:Sample series.svg|20x20px|class=noviewer]] [[Soil test#Soil testing|Sample series]]

* [[File:Screw plate test.svg|20x20px|class=noviewer]] [[Screw plate test]]

* [[Deformation monitoring]]
** [[File:Inclinometer.svg|20x20px|class=noviewer]] [[Inclinometer]]
** [[File:Settlement recordings.svg|20x20px|class=noviewer]] [[Soil consolidation|Settlement recordings]]

* [[File:Shear vane test.svg|20x20px|class=noviewer]] [[Shear vane test]]

* [[File:Simple sounding.svg|20x20px|class=noviewer]] [[Simple sounding]]

* [[File:Standard penetration test.svg|20x20px|class=noviewer]] [[Standard penetration test]]

* [[File:Total sounding.svg|20x20px|class=noviewer]] [[Total sounding]]

* [[File:Trial pit.svg|20x20px|class=noviewer]] [[Trial pit]]

* [[File:Visible rock.svg|20x20px|class=noviewer]] [[Bedrock|Visible bedrock]]

* [[Nuclear densometer|Nuclear densometer test]]

* [[Exploration geophysics]]

* [[Crosshole sonic logging]]

* [[Pile integrity test]]

* [[Wave equation analysis]]
}}
| group2 = [[Soil test|Laboratory testing]]
| list2 =
* [[Soil classification]]
* [[Atterberg limits]]
* [[California bearing ratio]]
* [[Direct shear test]]
* [[Hydrometer]]
* [[Proctor compaction test]]
* [[R-value (soils)|R-value]]
* [[Sieve analysis]]
* [[Triaxial shear test]]
* [[Oedometer test]]
* [[Hydraulic conductivity#Experimental approach|Hydraulic conductivity tests]]
* [[Water content#Measurement|Water content tests]]
}}

| group2 = [[Soil]]
| list2 =

{{Navbox |child
| groupwidth = 10.0em
| groupstyle = font-weight: normal;

| group1 = Types
| list1 =
* [[Clay]]
* [[Silt]]
* [[Sand]]
* [[Gravel]]
* [[Peat]]
* [[Loam]]
* [[Loess]]

| group2 = Properties
| list2 =

* [[Hydraulic conductivity]]
* [[Water content]]
* [[Void ratio]]
* [[Bulk density]]
* [[Thixotropy]]
* [[Reynolds' dilatancy]]
* [[Angle of repose]]
* [[Friction#Angle_of_friction|Friction angle]]
* [[Cohesion (geology)|Cohesion]]
* [[Porosity]]
* [[Permeability (earth sciences)|Permeability]]
* [[Specific storage]]
* [[Shear strength (soil)|Shear strength]]
* [[Soil liquefaction|Sensitivity]]
}}



| group4 = Structures ([[Soil-structure interaction|Interaction]])
| list4 =
{{Navbox |child
| groupwidth = 10.0em
| groupstyle = font-weight: normal;
| group1 = Natural features
| list1 =
*[[Topography]]
*[[Vegetation]]
*[[Terrain]]
*[[Topsoil]]
*[[Water table]]
*[[Bedrock]]
*[[Subgrade]]
*[[Subsoil]]

| group2 = [[Earthworks (engineering)|Earthworks]]
| list2 =
* Shoring structures
** [[Retaining wall]]s
** [[Gabion]]
** [[Ground freezing]]
** [[Mechanically stabilized earth]]
** [[Pressure grouting]]
** [[Slurry wall]]
** [[Soil nailing]]
** [[Tieback (geotechnical)|Tieback]]
*[[Land development]]
*[[Landfill]]
*[[Digging|Excavation]]
*[[Trench]]
*[[Embankment (earthworks)|Embankment]]
*[[Cut (earthworks)|Cut]]
*[[Causeway]]
*[[Terrace (earthworks)|Terracing]]
*[[Tunnel#Cut-and-cover|Cut-and-cover]]
*[[Cut and fill]]
*[[Fill dirt]]
*[[Grading (engineering)|Grading]]
*[[Land reclamation]]
*[[Track bed]]
*[[Erosion control]]
*[[Earth structure]]
*[[Expanded clay aggregate]]
*[[Crushed stone]]
*[[Geosynthetics]]
** [[Geotextile]]
** [[Geomembrane]]
** [[Geosynthetic clay liner]]
** [[Cellular confinement]]
*[[Infiltration (hydrology)|Infiltration]]

| group3 = [[Foundation (engineering)|Foundation]]s
| list3 =
* [[Shallow foundation|Shallow]]
* [[Deep foundation|Deep]]

}}
| group5 = [[Soil mechanics|Mechanics]]
| list5 =
{{Navbox |child
| groupwidth = 10.0em
| groupstyle = font-weight: normal;

| group1 = Forces
| list1 =
* [[Effective stress]]
* [[Pore water pressure]]
* [[Lateral earth pressure]]
* [[Overburden pressure]]
* [[Preconsolidation pressure]]
| group2 = Phenomena/ problems
| list2 =
* [[Permafrost]]
* [[Frost heaving]]
* [[Consolidation (soil)|Consolidation]]
* [[Soil compaction|Compaction]]
* [[Earthquake]]
** [[Response spectrum]]
** [[Seismic hazard]]
** [[S wave|Shear wave]]
* [[Landslide]] analysis
** [[Slope stability analysis|Stability analysis]]
** [[Landslide mitigation|Mitigation]]
** [[Landslide classification|Classification]]
** [[Sliding criterion (geotechnical engineering)|Sliding criterion]]
** [[Road#Slab_stabilization|Slab stabilisation]]
* [[Bearing capacity]] * [[Stress distribution in soil]]
}}

| group6 = [[Software|Numerical analysis software]]
| list6 =
* [[SEEP2D]]
* [[STABL]]
* [[SVFlux]]
* [[SVSlope]]
* [[UTEXAS]]
* [[Plaxis]]

| group7 = [[Geoprofessions|Related fields]]
| list7 =
* [[Geology]]
* [[Geochemistry]]
* [[Petrology]]
* [[Earthquake engineering]]
* [[Geomorphology]]
* [[Soil science]]
* [[Hydrology]]
* [[Hydrogeology]]
* [[Biogeography]]
* [[Earth materials]]
* [[Archaeology]]
* [[Agricultural science]]
** [[Agrology]]

}}<noinclude>
{{Navbox doc|3=
==See also==
* [[:Category:Geotechnical engineering]]
[[Category:Engineering navigational boxes]]
[[Category:Geology navigational boxes|Engineering]]
}}</noinclude>

Template:Earthquakes

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OpenDEM 1: 1 revision imported from :wikipedia:en:Template:Earthquakes

#REDIRECT [[Template:Earthquake sidebar]]

{{Redirect category shell|
{{R from move}}
}}

Seismotectonics

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OpenDEM 1: 1 revision imported from :wikipedia:en:Seismotectonics

'''Seismotectonics''' is the study of the relationship between the [[earthquakes]], active [[tectonics]] and individual [[Fault (geology)|faults]] of a region. It seeks to understand which faults are responsible for seismic activity in an area by analysing a combination of regional tectonics, recent instrumentally recorded events, accounts of historical earthquakes and [[Geomorphology|geomorphological]] evidence. This information can then be used to quantify the [[seismic hazard]] of an area.<ref name="Slejko_2012">{{Cite book |title=Recent Evolution and Seismicity of the Mediterranean Region |date=2012 |publisher=Springer |isbn=9789401120166 |editor-last=E. Boschi |editor-first=E. |chapter=A review of the Eastern Alps – Northern Dinarides Seismotectonics |editor-last2=Mantovani |editor-first2=E. |editor-last3=Morelli |editor-first3=A. |chapter-url=https://books.google.com/books?id=gbbvCAAAQBAJ&dq=seismotectonics+definition&pg=PA251}}</ref>

==Methodology==
A seismotectonic analysis of an area often involves the integration of disparate datasets.

===Regional tectonics===
An understanding of the regional tectonics of an area is likely to be derived from published [[geological map]]s, research publications on the [[structural geology|geological structure]] and [[seismic reflection]] profiles, where available, augmented by other [[geophysics|geophysical]] data.

In order to understand the seismic hazard of an area it is necessary not only to know where potentially active faults are, but also the orientation of the [[stress field]]. This is normally derived from a combination of earthquake data, borehole breakout analysis, direct stress measurement and the analysis of geologically young fault networks. The World Stress Map Project provides a useful online compilation of such data.<ref>[http://www.world-stress-map.org Website for the World Stress Map Project]</ref>

===Earthquakes===
====Instrumentally recorded events====
Since the early 20th century, sufficient information has been available from [[seismometers]] to allow the location, depth and magnitude of earthquakes to be calculated. In terms of identifying the fault responsible for an earthquake where there is no clear surface trace, recording the locations of [[aftershocks]] generally gives a strong indication of the strike of the fault.

In the last 30 years, it has been possible to routinely calculate [[focal mechanism]]s from teleseismic data. Catalogues of events with calculated focal mechanisms are now available online, such as the searchable catalogue from the [[National Earthquake Information Center|NEIC]].<ref>[https://web.archive.org/web/20070513001010/http://neic.usgs.gov/neis/sopar/ NEIC Moment Tensor and Broadband Source Parameter Search ]</ref> As focal mechanisms give two potential active fault plane orientations, other evidence is required to interpret the origin of an individual event. Although only available for a restricted time period, in areas of moderate to intense seismicity there is probably sufficient data to characterise the type of seismicity in an area, if not all the active structures.

====Historical records====
Attempts to understand the seismicity of an area require information from earthquakes before the era of instrumental recording.<ref>{{cite book|url=http://assets.cambridge.org/97805210/21876/frontmatter/9780521021876_frontmatter.pdf|last=Ambraseys|first=Nicolas|authorlink=Nicholas Ambraseys|author2=Melville, C.P. |year=1982|title=A History of Persian Earthquakes|publisher=Cambridge University Press|isbn=9780521021876}}</ref>{{rp|viii}} This requires a careful assessment of historical data in terms of their reliability. In most cases, all that can be derived is an estimate of the location and magnitude of the event. However, such data is needed to fill the gaps in the instrumental record, particularly in areas with either relatively low seismicity or where the repeat periods for major earthquakes is more than a hundred years.<ref>[http://faust.ingv.it/reports/1998-01-15/paola.htm Historical data on earthquakes and active faulting. The contribution of IRRS and IC to EC project FAUST (Contract ENV4-CT97-0428) ]</ref>

===Field investigations===
Information on the timing and magnitude of seismic events that occurred before instrumental recording can be obtained from excavations across faults that are thought to be seismically active and by studying recent sedimentary sequences for evidence of seismic activity such as [[seismite]]s<ref name="Migowski">{{cite journal|last=Migowski|first=C. |author2=Agnon A. |author3=Bookman R. |author4=Negendank J.F.W. |author5=Stein M|year=2004|title=Recurrence pattern of Holocene earthquakes along the Dead Sea transform revealed by varve-counting and radiocarbon dating of lacustrine sediments|journal=Earth and Planetary Science Letters|volume=222|issue=1 |pages=301–314|url=http://marsci.haifa.ac.il/margeo/bookmanLINK%203.PDF|accessdate=2009-12-29|bibcode = 2004E&PSL.222..301M |doi = 10.1016/j.epsl.2004.02.015 }}</ref> or [[tsunami deposit]]s.<ref name="Luque">{{cite journal|last=Luque|first=L. |author2=Lario J. |author3=Zazo C. |author4=Goy J.L. |author5=Dabrio C.J. |author6=Silva P.G.|year=2001|title=Tsunami deposits as paleoseismic indicators: examples from the Spanish coast|journal=Acta Geológica Hispánica|volume=36|issue=3–4|pages=197–211|url=http://www.raco.cat/index.php/ActaGeologica/article/viewFile/75644/107101|accessdate=2009-12-29}}</ref>

===Geomorphology===
Seismically [[active fault]]s and related fault generated [[Fold (geology)|folds]] have a direct effect on the geomorphology of a region. This may allow the direct identification of active structures not previously known. In some cases such observations can be used quantitatively to constrain the repeat period of major earthquakes, such as the [[raised beach]]es of [[Turakirae Head]] recording the history of coseismic uplift of the [[Rimutaka Range]] due to displacement on the [[Wairarapa Fault]] in [[North Island]], [[New Zealand]].<ref>[http://www.royalsociety.org.nz/Site/publish/Journals/nzjgg/2006/029.aspx McSaveney, M.J., Graham, I.J., Begg, J.G., Beu, A.G., Hull, A.G., Kyeong, K. & Zondervan, A. 2006. Late Holocene uplift of beach ridges at Turakirae Head, south Wellington coast, New Zealand. New Zealand Journal of Geology and Geophysics abstracts, 49, 337–358].</ref>

==See also==
*[[Seismology]]
*[[Plate tectonics]]

==References==
{{reflist}}

==External links==
*[http://www.geophysik.uni-muenchen.de/~igel/Lectures/Sedi/sedi_tectonics.ppt Presentation on Seismotectonics from Department of Geophysics, University of Munich]

{{Authority control}}

[[Category:Seismology]]
[[Category:Tectonics]]
[[Category:Structural geology]]

Seismological Society of America

2025-08-25T16:12:24Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Seismological_Society_of_America

{{Short description|International scientific society}}
{{Infobox organization
|name = Seismological Society of America
|image = Seismological Society of America (logo).jpg
|image_border =
|size =
|caption =
|map =
|msize =
|mcaption =
|abbreviation = SSA
|motto =
|formation = 1906
|extinction =
|type = Non-profit
|status =
|purpose = An international society devoted to the advancement of seismology and its applications in understanding and mitigating earthquake hazards and in imaging the structure of the Earth.
|headquarters = Albany, California
|location =
|region_served = global
|membership = 2,500 individuals; corporate members
|language =
|leader_title = President
|leader_name = Susan Bilek<ref>{{cite news
| title=NMT professor is president-elect of Seismological Society of America
| date=July 29, 2024 | work=New Mexico Tech
| url=https://www.nmt.edu/news/2024/susan-bilek-SSA.php
| access-date=2025-08-23 }}</ref>
|main_organ =
|parent_organization =
|affiliations =
|num_staff = 8
|num_volunteers =
|budget =
|website = http://www.seismosoc.org
|remarks =
}}

The '''Seismological Society of America''' ('''SSA''') is an international [[Learned society|scientific society]] devoted to the advancement of seismology and the understanding of earthquakes for the benefit of society. Founded in 1906, the society has members throughout the world representing seismologists and other geophysicists, geologists, engineers, insurers, and policy-makers in preparedness and safety.

== History ==
The society was established by academic, government, and other scientific and engineering professionals in the months following the April 18th [[1906 San Francisco earthquake|San Francisco earthquake]], with the first meeting of the Board of Directors taking place on December 1, 1906.<ref>{{cite journal
| title=History of the Seismological Society of America
| first=B. F. Jr. | last=Howell
| journal=Seismological Research Letters
| year=2002 | volume=73 | issue=1 | pages=70–83
| doi=10.1785/gssrl.73.1.70 | bibcode=2002SeiRL..73...70H }}</ref>

== Publications ==
The Seismological Society of America publishes the ''[[Bulletin of the Seismological Society of America]]'' (''BSSA''), a journal of research in earthquake seismology and related disciplines since 1911, and ''Seismological Research Letters'' (''SRL''), which serves as a forum for informal communication among seismologists, as well as between seismologists and those non-specialists interested in seismology and related disciplines.

The ''Bulletin of the Seismological Society of America'' (''BSSA''), first issued in 1911, is a bimonthly peer-reviewed journal of original seismological research as well as reviews which summarize topics of seismic research. Offering highly detailed, in-depth, and theoretical treatment of its subject matter by international authors, this journal appeals to an audience of specialists in the field of seismology.

''Seismological Research Letters'' (''SRL''), first issued in 1987, is a peer-reviewed journal published bimonthly both in print and online.<ref>{{Cite web |title=Seismological Research Letters {{!}} Seismological Society of America |url=https://www.seismosoc.org/publications/srl/ |access-date=2023-02-22 |publisher=Seismological Society of America }}</ref> This journal appeals to a broader international audience of geoscientists beyond seismology as well as a possible crossover audience beyond the geoscientific specialties. As such, this journal publishes both original research and, to a lesser degree, educational, historical, and emerging topics of seismological science. Original research of similar scope can be found in both journals (''BSSA'' above and ''SRL''), but ''SRL'' papers tend to be less theoretical and more experimental in nature, as well as more timely.

''The Seismic Record'' (TSR), established in 2021, publishes short peer-reviewed articles on the breadth of seismology and earthquake science. The articles, each no more than six published pages in total, cover recent events and current topics of strong significance, warranting rapid peer review and publication.

SSA follows a general policy of online open access permitting authors to post their work online at their discretion anytime 12 months after its initial publication by SSA.

== Meetings ==
The society hosts an annual meeting every April. The meeting is open to anyone. SSA members receive a discount on their meeting registration. The Eastern Section of SSA hosts an annual meeting each fall.

=== Past and future annual meetings ===
{{div col}}
* 27–30 April 2021 – Virtual
* 23–26 April 2019 – Seattle, Washington
* 14–17 May 2018 – Miami, Florida
* 18–20 April 2017 – Denver, Colorado
* 20–22 April 2016 – Reno, Nevada
* 21–23 April 2015 – Pasadena, California
* 30 April-2 May 2014 – Anchorage, Alaska
* 17–19 April 2013 – Salt Lake City, Utah
* 17–19 April 2012 – San Diego, California
* 13–15 April 2011 – Memphis, Tennessee
* 21–23 April 2010 – Portland, Oregon
* 8–10 April 2009 – Monterey, California
* 16–18 April 2008 – Santa Fe, New Mexico
* 11–13 April 2007 – Kona, Hawaii
* 18–22 April 2006 – San Francisco, California
* 27–29 April 2005 – Lake Tahoe, Nevada
* 14–16 April 2004 – Palm Springs, California
* 30 April-3 May 2003 – San Juan, Puerto Rico
* 17–19 April 2002 – Victoria, British Columbia (Canada)
* 18–20 April 2001 – San Francisco, California
* 10–12 April 2000 – San Diego, California
* 3–5 May 1999 – Seattle, Washington
* 16–18 March 1998 – Boulder, Colorado
* 9–11 April 1997 – Honolulu, Hawaii
* 1–3 April 1996 – St. Louis, Missouri
* 22–24 March 1995 – El Paso, Texas
* 5–7 April 1994 – Pasadena, California
* 14–16 April 1993 – Ixtapa-Zihuatanejo, Mexico
* 14–16 April 1992 – Santa Fe, New Mexico
* 25–27 March 1991 – San Francisco, California
* 2–4 May 1990 – Santa Cruz, California
* 16–19 May 1973 – Golden, Colorado
*
{{div col end}}

==Past presidents==
Past presidents of the Seismological Society of America:<ref>{{cite web
| title=Presidents of the Society
| publisher=Seismological Society of America
| url=https://www.seismosoc.org/inside/history/presidents-society/
| access-date=2024-03-01
}}</ref>
<div style="column-width:15em">
* Heather DeShon, 2024<ref>{{cite news
| title=Congratulations to Heather DeShon, recently elected president of the Seismological Society of America
| date=April 24, 2023 | publisher=SMU, Dedman College of Humanities and Sciences
| url=https://blog.smu.edu/dedmancollege/2023/04/24/congratulations-to-heather-deshon-recently-elected-president-of-the-seismological-society-of-america/
| access-date=2024-03-01 }}</ref>
* Ruth Harris, 2023
* Peggy Hellweg, 2022<ref name=SSA_2022>{{cite web
| title=2022 Annual Meeting | date=April 19, 2022
| publisher=Seismological Society of America
| url=https://meetings.seismosoc.org/wp-content/uploads/2022/07/SSA_2022AM-Program-final.pdf
| access-date=2024-03-01 }}</ref>
* John Townend, 2021<ref name=SSA_2022/>
* Bill Walter, 2020
* [[Susan Hough]], 2019
* Peter Shearer, 2018
* Andy Michael, 2017
* Jim Mori, 2016
* [[Ruth Harris (scientist)|Ruth Harris]], 2015
* Lisa Grant Ludwig, 2014
* Tom Jordan, 2013
* Christa von Hillebrandt–Andrade, 2011–12
* [[Richard Aster|Richard C. Aster]], 2009–10
* [[William Ellsworth (geophysicist)|William L. Ellsworth]], 2007–08
* Michael Fehler, 2005–06
* Stephen D. Malone, 2003–04
* [[Gail Atkinson|Gail M. Atkinson]], 2001–02
* [[Terry Wallace (geophysicist)|Terry C. Wallace Jr.]], 1999–2000
* Ralph Archuleta, 1997–98
* Steve Wesnousky, 1995–96
* Tom Heaton, 1993–94
* Arch C. Johnston, 1992
* Robin K. McGuire, 1991
* Charles A. Langston, 1990
* John Filson, 1989
* Shelton S. Alexander, 1988
* David G. Harkrider, 1987
* [[C. Allin Cornell]], 1986
* [[Hiroo Kanamori]], 1985
* Gilbert A. Bollinger, 1984
* Robert M. Hamilton, 1983
* Lloyd S. Cluff, 1982
* Alan S. Ryall Jr., 1981
* Paul C. Jennings, 1980
* [[Keiiti Aki]], 1979
* James C. Savage, 1978
* [[George W. Housner]], 1977
* Otto W. Nuttli, 1976
* [[Clarence Allen (geologist)|Clarence R. Allen]], 1975
* [[Bruce Bolt|Bruce A. Bolt]], 1974
* Don Tocher, 1973
* Carl Kisslinger, 1972
* [[Donald E. Hudson]], 1971
* James N. Brune, 1970
* [[Norman Haskell|Norman A. Haskell]], 1969
* Joseph W. Berg Jr., 1968
* Karl V. Steinbrugge, 1967
* [[Jerry P. Eaton]], 1966
* William U. Stauder, S.J., 1965
* [[Jack Oliver (scientist)|Jack E. Oliver]], 1964
* B. F. Howell Jr., 1963
* [[Frank Press]], 1962
* Dean S. Carder, 1961
* James T. Wilson, 1960
* [[Charles Richter|Charles F. Richter]], 1959
* [[Hugo Benioff]], 1958
* [[Perry Byerly]], 1957
* [[Maurice Ewing]], 1955–56
* Lydik S. Jacobsen, 1953–54
* John P. Buwalda, 1951–52
* Frank Neumann, 1949–50
* [[Eliot Blackwelder]], 1948
* [[Beno Gutenberg]], 1945–47
* Walter H. Kirkbride, 1943–44
* Ernest A. Hodgson, 1941–42
* Robert E. Andrews, 1939–40
* [[Nicholas H. Heck]], 1936–38
* [[Sidney Dean Townley|Sidney D. Townley]], 1935
* [[George Louderback|George D. Louderback]], 1930–34
* [[James B. Macelwane]], S.J., 1928–29
* [[Bailey Willis]], 1921–27
* [[Otto Julius Klotz|Otto Klotz]], 1920
* [[Charles F. Marvin]], 1918–19
* [[Jay Backus Woodworth]], 1916–17
* [[Alexander George McAdie|Alexander G. McAdie]], 1915
* [[George Louderback|George D. Louderback]], 1914
* [[Harry Fielding Reid|Harry F. Reid]], 1912–13
* [[John Casper Branner|John C. Branner]], 1911
* [[Andrew Lawson|Andrew C. Lawson]], 1910
* [[George Davidson (geographer)|George Davidson]], 1906–09
</div>

==See also==
*[[American Geological Institute]]
*[[Geological Society of America]]
*[[IRIS Consortium]]
*[[List of geoscience organizations]]

==References==
{{reflist}}

'''Sources'''
{{refbegin}}
* {{citation|title=History of the Seismological Society of America|url=http://www.seismosoc.org/inside/history/byerly_history.php|first=P.|last=Byerly|year=1964|journal=[[Bulletin of the Seismological Society of America]]|publisher=Seismological Society of America|volume=54|number=6|pages=1723–1741|doi=10.1785/BSSA05406A1723|bibcode=1964BuSSA..54.1723B|url-access=subscription}}
{{refend}}

==External links==
*[http://www.seismosoc.org SSA official website]

{{authority control}}

[[Category:Geology societies]]
[[Category:Geophysics societies]]
[[Category:Non-profit organizations based in California]]
[[Category:Scientific societies based in the United States]]
[[Category:Organizations based in Alameda County, California]]
[[Category:Albany, California]]
[[Category:Scientific organizations established in 1906]]
[[Category:1906 establishments in California]]

IRIS Consortium

2025-08-25T16:12:23Z

OpenDEM 1: 1 revision imported from :wikipedia:en:IRIS_Consortium

{{Short description|Former research group using seismographic data}}
{{Infobox organization
| name = Incorporated Research Institutions for Seismology
| image_size = 180px
| logo = LOGO_Iris_color_screen.png
| map =
| map_size = 
| map_alt = 
| map_caption =
| map2 =
| type = [[501(c)(3)]]
| tax_id = 
| registration_id =
| founded_date = {{Start date and age|1984|10}}
| founder =
| dissolved = 
| location = [[William T. Golden Center for Science and Engineering]] Washington, D.C.
| addnl_location =
| coordinates = 
| origins =
| key_people = Robert Woodward, President; Richard C. Aster, Chair of the Board of Directors
| area_served =
| products =
| services = [[Research]], [[education]]
| focus =
| mission =
| method =
| revenue =
| disbursed =
| expenses =
| num_volunteers =
| num_employees =
| num_members = 290 (2018)
| affiliations =
| subsid =
| languages = [[English language|English]]
| website = {{URL|https://www.iris.edu/}}
| footnotes =
}}

'''IRIS''' (Incorporated Research Institutions for Seismology) was a university research consortium dedicated to exploring the Earth's interior through the collection and distribution of seismographic data. It operated the U.S. National Science Foundation's [[Seismological Facility for the Advancement of Geoscience]] (SAGE Facility) until 2023. IRIS programs contributed to scholarly research, [[education]], [[earthquake]] hazard mitigation, and the verification of a [[Comprehensive Nuclear-Test-Ban Treaty]]. Support for IRIS came from the [[National Science Foundation]], other federal agencies, universities, and private [[foundation (charity)|foundations]]. IRIS supported five major components:

* The Data Management Center (DMC<ref>{{Cite web|url=http://ds.iris.edu/ds/nodes/dmc/|title=IRIS: Data Management Center|website=ds.iris.edu|access-date=2019-12-24}}</ref>)
* The Portable Array Seismic Studies of the Continental [[Lithosphere]] ([[EarthScope Primary Instrument Center|PASSCAL]]<ref>{{Cite web|url=https://www.iris.edu/hq/programs/passcal|title=Portable Array Seismic Studies of the Continental Lithosphere {{!}} IRIS|publisher=IRIS Consortium|access-date=2019-12-24}}</ref>)
* The [[Global Seismographic Network]] (GSN<ref>{{Cite web|url=https://www.iris.edu/hq/programs/gsn|title=Global Seismographic Network {{!}} IRIS|publisher=IRIS Consortium|access-date=2019-12-24}}</ref>)
* The Transportable Array ([[USArray|USARRAY]]<ref>{{Cite web|url=http://www.usarray.org/|title=USArray|website=usarray.org|access-date=2019-12-24}}</ref>)
* Education and Public Outreach Program (EPO<ref>{{Cite web|url=https://www.iris.edu/hq/programs/epo|title=Education and Public Outreach {{!}} IRIS|publisher=IRIS Consortium|access-date=2019-12-24}}</ref>)

IRIS maintained a corporate office in Washington, D.C.

IRIS's Education and Public Outreach Program offered animations, videos, lessons, software, posters, and fact sheets to help teachers and the general public learn more about seismology and earth science and understand it better. The goal is to get more people interested in careers in geophysics.

IRIS is listed in the [[Registry of Research Data Repositories]] re3data.org.<ref>{{cite web|title=IRIS Entry in re3data.org|url=http://service.re3data.org/repository/r3d100010268|website=re3data.org|access-date=21 August 2014}}</ref>

On January 1, 2023, IRIS merged with [[UNAVCO]] to form the [[EarthScope Consortium]] that now operates both the U.S. National Science Foundation's [[Seismological_Facility_for_the_Advancement_of_Geoscience|SAGE]] and [[Geodetic_Facility_for_the_Advancement_of_Geoscience|GAGE]] Facilities through 2025.<ref>{{Cite web|title=Joining Forces|url=https://sites.google.com/iris.edu/united/home|access-date=2023-08-08|website=sites.google.com}}</ref>

==History==
{{Unreferenced section|date=November 2022}}
In 1959, the United States Government launched a research effort aimed at improving national capabilities to detect and identify foreign nuclear explosions detonated underground and at high altitudes. The resultant [[World-Wide Standardized Seismograph Network]] (WWSSN) was a program successful beyond its original remit. It provided seismological data for its intended purpose as well as for the emerging concept of [[plate tectonics]]. Initially operated by the Defense Department, by 1973 operations were transferred to the [[United States Geological Survey]] (USGS). A collaboration with the IRIS Consortium began in 1984 as a result of a need to expand and succeed the WWSSN with the Global Seismographic Network (GSN). The GSN, originally funded entirely by the USGS under the [[National Earthquake Hazards Reduction Program]] (NEHRP), is now jointly supported by the [[National Science Foundation]].

==See also==
{{div col}}
*[[EarthScope]]
*[[Geophysics]]
*[[POLARIS (seismology)|POLARIS]]
*[[Reflection seismology]]
*[[Seismology]]
*[[Seismometer]]
*[[UNAVCO]]
*[[Volcanology]]
{{div col end}}

==References==
{{Reflist}}

==Further reading==
* {{cite journal|last=Aster|first=R.|last2=Beaudoin|first2=B.|last3=Hole|first3=J.|last4=Fouch|first4=M.|last5=Fowler|first5=J.|last6=James|first6=D.|title=IRIS Seismology Program marks 20 years of discovery|journal=Eos, Transactions American Geophysical Union|volume=86|issue=17|date=2005-04-26|issn=0096-3941|doi=10.1029/2005EO170002|doi-access=free|pages=171–172|url=https://onlinelibrary.wiley.com/doi/pdfdirect/10.1029/2005EO170002|url-access=subscription}}
* {{cite journal|last=Smith|first=Stewart W.|title=IRIS—A university consortium for seismology|journal=Reviews of Geophysics|volume=25|issue=6|date=1987|issn=8755-1209|doi=10.1029/RG025i006p01203|pages=1203–1207}}
* {{cite journal|author=van der Vink GE|title=The role of seismologists in debates over the Comprehensive Test Ban Treaty|journal=Annals of the New York Academy of Sciences|year=1998|volume=866|issue=1|pages=84–113|doi=10.1111/j.1749-6632.1998.tb09148.x}}

==External links==
*{{Official website|http://www.iris.edu}}

{{Authority control}}

[[Category:Seismological observatories, organisations and projects]]
[[Category:Research organizations in the United States]]
[[Category:College and university associations and consortia in the United States]]

Helioseismology

2025-08-25T16:12:23Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Helioseismology

{{Short description|Study of the structure and dynamics of the Sun through its oscillation}}
'''Helioseismology''' is the study of the structure and dynamics of the [[Sun]] through its oscillations. These are principally caused by sound waves that are continuously driven and damped by convection near the Sun's surface. It is similar to [[seismology|geoseismology]], or [[asteroseismology]], which are respectively the studies of the [[Earth]] or [[star]]s through their oscillations. While the Sun's oscillations were first detected in the early 1960s, it was only in the mid-1970s that it was realized that the oscillations propagated throughout the Sun and could allow scientists to study the Sun's deep interior. The term was coined by [[Douglas Gough]] in the 90s. The modern field is separated into '''global helioseismology''', which studies the Sun's resonant modes directly,<ref>{{Citation | last1 = Gough | first1 = D.O. | last2 = Kosovichev | first2 = A.G. | last3 = Toomre | first3 = J. | last4 = Anderson | first4 = E.R. | last5 = Antia | first5 = H.M. | last6 = Basu | first6 = S. | last7 = Chaboyer | first7 = B. | last8 = Chitre | first8 = S.M. | last9 = Christensen-Dalsgaard | first9 = J. | last10 = Dziembowski | first10 = W.A. | last11 = Eff-Darwich | first11 = A. | last12 = Elliott | first12 = J.R. | last13 = Giles | first13 = P. | last14 = Goode | first14 = P.R. | last15 = Guzik | first15 = J.A. | last16 = Harvey | first16 = J.W. | last17 = Hill | first17 = F. | last18 = Leibacher | first18 = J.W. | last19 = Montiero | first19 = M.J.P.F.G. | last20 = Richard | first20 = O. | last21 = Sekii | first21 = T. | last22 = Shibahashi | first22 = H. | last23 = Takata | first23 = M. | last24 = Thompson | first24 = M.J. | last25 = Vauclair | first25 = S. | last26 = Vorontsov | first26 = S.V. |display-authors=3 | title = The seismic structure of the Sun | volume = 272 | pages = 1296–1300 | year = 1996 | doi = 10.1126/science.272.5266.1296 | journal = Science | issue = 5266 | pmid = 8662458 | bibcode = 1996Sci...272.1296G | s2cid = 15996636 }}</ref> and '''local helioseismology''', which studies the propagation of the component waves near the Sun's surface.<ref name="gb2005">{{Citation | last1 = Gizon | first1 = L. | last2 = Birch | first2 = A. C. | title = Local Helioseismology | year = 2005 | journal = Living Reviews in Solar Physics | volume = 2 | issue = 1 | page = 6| bibcode = 2005LRSP....2....6G| doi = 10.12942/lrsp-2005-6 | doi-access = free }}</ref>

Helioseismology has contributed to a number of scientific breakthroughs. The most notable was to show that the anomaly in the predicted neutrino flux from the Sun could not be caused by flaws in stellar models and must instead be a problem of [[particle physics]]. The so-called [[solar neutrino problem]] was ultimately resolved by [[neutrino oscillations]].<ref>{{Citation | last1 = Fukuda | first1 = Y. | last2 = Super-Kamiokande Collaboration | title = Evidence for oscillation of atmospheric neutrinos | journal = Phys. Rev. Lett. | volume = 81 | number = 8 | pages = 1562–1567 | year = 1998 | doi = 10.1103/PhysRevLett.81.1562 | arxiv = hep-ex/9807003 | doi-access = free | bibcode = 1998PhRvL..81.1562F }}</ref><ref>{{Citation | last1 = Bahcall | first1 = J. N. | last2 = Concha | first2 = Gonzalez-Garcia M. | last3 = Pe | first3 = na-Garay C. | s2cid = 6595480 | title = Global analysis of solar neutrino oscillations including SNO CC measurement | year = 2001 | journal = Journal of High Energy Physics | volume = 2001 | issue = 8 | page = 014| arxiv = hep-ph/0106258 | bibcode = 2001JHEP...08..014B| doi = 10.1088/1126-6708/2001/08/014 }}</ref><ref>{{Citation | last1 = Bahcall | first1 = J. N. | s2cid = 205018839 | title = High-energy physics: Neutrinos reveal split personalities | year = 2001 | journal = Nature | volume = 412 | issue = 6842 | pages = 29–31| bibcode = 2001Natur.412...29B| pmid = 11452285 | doi = 10.1038/35083665 }}</ref> The experimental discovery of neutrino oscillations was recognized by the 2015 [[Nobel Prize for Physics]].<ref>{{cite news | url=https://www.bbc.com/news/science-environment-34443695 | title=Neutrino 'flip' wins physics Nobel Prize | journal=BBC News | date=6 October 2015 | author=Webb, Jonathan}}</ref> Helioseismology also allowed accurate measurements of the quadrupole (and higher-order) moments of the Sun's gravitational potential,<ref name= "natureomega">{{Citation | last1 = Duvall | first1 = T.L. Jr | last2 = Dziembowski | first2 = W.A. | last3 = Goode | first3 = P.R. | last4 = Gough | first4 = D.O. | last5 = Harvey | first5 = J.W. | last6 = Leibacher | first6 = J.W. | s2cid = 4310140 | title = The internal rotation of the Sun | year = 1984 | journal = Nature | volume = 310 | issue = 5972 | pages = 22–25| doi = 10.1038/310022a0 | bibcode = 1984Natur.310...22D }}</ref><ref>{{Citation | last1 = Pijpers | first1 = F.P. | journal = Mon. Not. R. Astron. Soc. | volume = 297 | issue = 3 | pages = L76–L80 | year = 1998 | title = Helioseismic determination of the solar gravitational quadrupole moment | doi = 10.1046/j.1365-8711.1998.01801.x | doi-access = free | arxiv = astro-ph/9804258 | bibcode = 1998MNRAS.297L..76P | s2cid = 14179539 }}</ref><ref>{{Citation | last1 = Antia | first1 = H.M. | last2 = Chitre | first2 = S.M. | last3 = Gough | first3 = D.O. | journal = Astron. Astrophys. | volume = 477 | pages = 657–663 | year = 2008 | title = Temporal variations in the Sun's rotational kinetic energy | issue = 2 | bibcode = 2008A&A...477..657A | doi = 10.1051/0004-6361:20078209 | arxiv = 0711.0799 | doi-access = free }}</ref> which are consistent with [[General Relativity]]. The first helioseismic calculations of the Sun's internal rotation profile showed a rough separation into a rigidly-rotating core and differentially-rotating envelope. The boundary layer is now known as the [[tachocline]]<ref>{{Citation | last1 = Spiegel | first1 = E. A. | last2 = Zahn | first2 = J.-P. | title = The solar tachocline | year = 1992 | journal = Astronomy and Astrophysics | volume = 265 | page = 106| bibcode = 1992A&A...265..106S}}</ref> and is thought to be a key component for the [[solar dynamo]].<ref>{{Citation | last1 = Fan | first1 = Y. | title = Magnetic Fields in the Solar Convection Zone | year = 2009 | journal = Living Reviews in Solar Physics | volume = 6 | issue = 1 | article-number = 4| bibcode = 2009LRSP....6....4F| doi = 10.12942/lrsp-2009-4 | doi-access = free }}</ref> Although it roughly coincides with the base of the solar convection zone — also inferred through helioseismology — it is conceptually distinct, being a boundary layer in which there is a meridional flow connected with the convection zone and driven by the interplay between baroclinicity and Maxwell stresses.<ref>{{Citation | last1 = Gough |first1 = D.O. |last2 = McIntyre | first2 = M.E. | author2-link=Michael E. McIntyre | s2cid = 1365619 | title = Inevitability of a magnetic field in the Sun's interior | year = 1998 | journal = Nature | volume = 394 |issue = 6695 | page = 755 | bibcode = 1998Natur.394..755G | doi = 10.1038/29472 }}</ref>

Helioseismology benefits most from continuous monitoring of the Sun, which began first with uninterrupted observations from near the [[South Pole]] over the austral summer.<ref name = "Grecsouthpole">{{Citation |last1 = Grec | first1 = G. | last2 = Fossat | first2 = E. | last3 = Pomerantz | first3 = M. |author-link3=Martin A. Pomerantz | s2cid = 4345313 | title = Solar oscillations: full disk observations from the geographic South Pole | journal = Nature | volume = 288 | pages = 541–544 | year = 1980 | issue = 5791 | doi = 10.1038/288541a0 | bibcode = 1980Natur.288..541G }}</ref><ref name="duvall_southpole1983">{{Citation | last1 = Duvall | first1 = Jr. T. L. | last2 = Harvey | first2 = J. W. | s2cid = 4274994 | title = Observations of solar oscillations of low and intermediate degree | year = 1983 | journal = Nature | volume = 302 | issue = 5903 | page = 24| bibcode = 1983Natur.302...24D| doi = 10.1038/302024a0 }}</ref> In addition, observations over multiple solar cycles have allowed helioseismologists to study changes in the Sun's structure over decades. These studies are made possible by global telescope networks like the [[Global Oscillations Network Group]] (GONG) and the [[Birmingham Solar Oscillations Network]] (BiSON), which have been operating for over several decades.

== Types of solar oscillation ==

[[File:ModelS pmode n14 l20 m16.png|thumb|Illustration of a solar pressure mode (p mode) with radial order n=14, angular degree l=20 and azimuthal order m=16. The surface shows the corresponding spherical harmonic. The interior shows the radial displacement computed using a standard solar model.<ref>{{Citation | last1 = Christensen-Dalsgaard | first1 = J. | last2 = Dappen | first2 = W. | last3 = Ajukov | first3 = S. V. | last4 = Anderson | first4 = E. R. | last5 = Antia | first5 = H. M. | last6 = Basu | first6 = S. | last7 = Baturin | first7 = V. A. | last8 = Berthomieu | first8 = G. | last9 = Chaboyer | first9 = B. | last10 = Chitre | first10 = S. M. | last11 = Cox | first11 = A. N. | last12 = Demarque | first12 = P. | last13 = Donatowicz | first13 = J. | last14 = Dziembowski | first14 = W. A. | last15 = Gabriel | first15 = M. | last16 = Gough | first16 = D. O. | last17 = Guenther | first17 = D. B. | last18 = Guzik | first18 = J. A. | last19 = Harvey | first19 = J. W. | last20 = Hill | first20 = F. | last21 = Houdek | first21 = G. | last22 = Iglesias | first22 = C. A. | last23 = Kosovichev | first23 = A. G. | last24 = Leibacher | first24 = J. W. | last25 = Morel | first25 = P. | last26 = Proffitt | first26 = C. R. | last27 = Provost | first27 = J. | last28 = Reiter | first28 = J. | last29 = Rhodes | first29 = Jr. E. J. | last30 = Rogers | first30 = F. J. | last31 = Roxburgh | first31 = I. W. | last32 = Thompson | first32 = M. J. | last33 = Ulrich | first33 = R. K. | title = The Current State of Solar Modeling | year = 1996 | journal = Science | volume = 272 | issue = 5266 | pages = 1286–92| bibcode = 1996Sci...272.1286C| pmid = 8662456 | doi = 10.1126/science.272.5266.1286 | s2cid = 35469049 }}</ref> Note that the increase in the speed of sound as waves approach the center of the Sun causes a corresponding increase in the acoustic wavelength.]]

Solar oscillation modes are interpreted as resonant vibrations of a roughly spherically symmetric self-gravitating fluid in hydrostatic equilibrium. Each mode can then be represented approximately as the product of a function of radius <math>r</math> and a spherical harmonic <math>Y^m_l(\theta,\phi)</math>, and consequently can be characterized by the three quantum numbers which label:

* the number of nodal shells in radius, known as the ''radial order'' <math>n</math>;
* the total number of nodal circles on each spherical shell, known as the ''angular degree'' <math>\ell</math>; and
* the number of those nodal circles that are longitudinal, known as the ''azimuthal order'' <math>m</math>.

It can be shown that the oscillations are separated into two categories: interior oscillations and a special category of surface oscillations. More specifically, there are:

=== Pressure modes (p modes) ===

Pressure modes are in essence standing sound waves. The dominant restoring force is the pressure (rather than buoyancy), hence the name. All the solar oscillations that are used for inferences about the interior are p modes, with frequencies between about 1 and 5 millihertz and angular degrees ranging from zero (purely radial motion) to order <math>10^3</math>. Broadly speaking, their energy densities vary with radius inversely proportional to the sound speed, so their resonant frequencies are determined predominantly by the outer regions of the Sun. Consequently it is difficult to infer from them the structure of the solar core.

[[File:Propagation diagram.png|thumb|A propagation diagram for a standard solar model<ref>{{Citation | last1 = Christensen-Dalsgaard | first1 = J. | last2 = Dappen | first2 = W. | last3 = Ajukov | first3 = S. V. and | title = The Current State of Solar Modeling | year = 1996 | journal = Science | volume = 272 | issue = 5266 | pages = 1286–1292| bibcode = 1996Sci...272.1286C|doi = 10.1126/science.272.5266.1286 | pmid = 8662456 | s2cid = 35469049 }}</ref> showing where oscillations have a g-mode character (blue) or where dipole modes have a p-mode character (orange). The dashed line shows the acoustic cut-off frequency, computed from more precise modelling, and above which modes are not trapped in the star, and roughly-speaking do not resonate.]]

=== {{anchor|g modes}}Gravity modes (g modes) ===

Gravity modes are confined to convectively stable regions, either the radiative interior or the atmosphere. The restoring force is predominantly buoyancy, and thus indirectly gravity, from which they take their name. They are [[evanescent wave|evanescent]] in the convection zone, and therefore interior modes have tiny amplitudes at the surface and are extremely difficult to detect and identify.<ref>{{Citation | last1 = Appourchaux | first1 = T. | last2 = Belkacem | first2 = K. | last3 = Broomhall | first3 = A.-M. | last4 = Chaplin | first4 = W. J. | last5 = Gough | first5 = D. O. | last6 = Houdek | first6 = G. | last7 = Provost | first7 = J. | last8 = Baudin | first8 = F. | last9 = Boumier | first9 = P. | last10 = Elsworth | first10 = Y. | last11 = Garc\'\ia | first11 = R. A. | last12 = Andersen | first12 = B. N. | last13 = Finsterle | first13 = W. | last14 = Fr\ohlich | first14 = C. | last15 = Gabriel | first15 = A. | last16 = Grec | first16 = G. | last17 = Jiménez | first17 = A. | last18 = Kosovichev | first18 = A. | last19 = Sekii | first19 = T. | last20 = Toutain | first20 = T. | last21 = Turck-Chi\`eze | first21 = S. | s2cid = 119272874 | title = The quest for the solar g modes | year = 2010 | journal = Astronomy and Astrophysics Review | volume = 18 | issue = 1–2 | page = 197| arxiv = 0910.0848 | bibcode = 2010A&ARv..18..197A| doi = 10.1007/s00159-009-0027-z }}</ref> It has long been recognized that measurement of even just a few g modes could substantially increase our knowledge of the deep interior of the Sun.<ref name = "snowmass">{{Citation | last1 = Gough | first1 = D.O. | title = Solar inverse theory | journal = Solar Seismology from Space (Ed. R.K. Ulrich, JPL Publ., Pasadena) | volume = 84-84 | pages = 49–78 | year = 1984 |
bibcode = 1984sses.nasa...49G }}</ref> However, no individual g mode has yet been unambiguously measured, although indirect detections have been both claimed<ref>{{Citation | last1 = Garc\'\ia | first1 = R. A. | last2 = Turck-Chi\`eze | first2 = S. | last3 = Jiménez-Reyes | first3 = S. J. | last4 = Ballot | first4 = J. | last5 = Pallé | first5 = P. L. | last6 = Eff-Darwich | first6 = A. | last7 = Mathur | first7 = S. | last8 = Provost | first8 = J. | s2cid = 35285705 | title = Tracking Solar Gravity Modes: The Dynamics of the Solar Core | year = 2007 | journal = Science | volume = 316 | issue = 5831 | pages = 1591–3| bibcode = 2007Sci...316.1591G| pmid = 17478682 | doi = 10.1126/science.1140598 }}</ref><ref>{{Citation | last1 = Fossat | first1 = E. | last2 = Boumier | first2 = P. | last3 = Corbard | first3 = T. | last4 = Provost | first4 = J. | last5 = Salabert | first5 = D. | last6 = Schmider | first6 = F. X. | last7 = Gabriel | first7 = A. H. | last8 = Grec | first8 = G. | last9 = Renaud | first9 = C. | last10 = Robillot | first10 = J. M. | last11 = Roca-Cortés | first11 = T. | last12 = Turck-Chi\`eze | first12 = S. | last13 = Ulrich | first13 = R. K. | last14 = Lazrek | first14 = M. | s2cid = 53498421 | title = Asymptotic g modes: Evidence for a rapid rotation of the solar core | year = 2017 | journal = Astronomy and Astrophysics | volume = 604 | pages = A40| arxiv = 1708.00259 | bibcode = 2017A&A...604A..40F| doi = 10.1051/0004-6361/201730460 }}</ref> and challenged.<ref>{{Citation | last1 = Schunker | first1 = H. | last2 = Schou | first2 = J. | last3 = Gaulme | first3 = P. | last4 = Gizon | first4 = L. | journal = Solar Physics | volume = 293 | page = 95| year = 2018 | title = Fragile Detection of Solar g-Modes by Fossat et al. | issue = 6 | doi = 10.1007/s11207-018-1313-6 | arxiv = 1804.04407 | bibcode = 2018SoPh..293...95S | doi-access = free }}</ref><ref>{{Citation | last1 = Scherrer | first1 = P. H. | last2 = Gough | first2 = D. O. | s2cid = 102351083 | journal = Astrophysical Journal | title = A critical evaluation of recent claims concerning solar rotation | volume = 877 | pages =42–53 | year = 2019 | issue = 1 | doi = 10.3847/1538-4357/ab13ad | arxiv = 1904.02820 | bibcode = 2019ApJ...877...42S | doi-access = free }}</ref> Additionally, there can be similar gravity modes confined to the convectively stable atmosphere.
{{For|more|Phoebus group}}

=== Surface gravity modes (f modes) ===

Surface gravity waves are analogous to waves in deep water, having the property that the Lagrangian pressure perturbation is essentially zero. They are of high degree <math>\ell</math>, penetrating a characteristic distance <math>R/\ell</math>, where <math>R</math> is the solar radius. To good approximation, they obey the so-called deep-water-wave dispersion law: <math>\omega^2=gk_{\rm h}</math>, irrespective of the stratification of the Sun, where <math>\omega</math> is the angular frequency, <math>g</math> is the surface gravity and <math>k_{\rm h} = \ell/R</math> is the horizontal wavenumber,<ref>{{Citation | last1 = Gough | first1 = D.O. | title = A review of the theory of solar oscillations and its implications concerning the internal structure of the Sun | journal = In Pulsations in Classical and Cataclysmic Variable Stars (Ed. J.P. Cox & C.J. Hansen, JILA, Boulder) | pages = 117–137 | year = 1982 | bibcode = 1982pccv.conf..117G }}</ref> and tend asymptotically to that relation as <math>k_{\rm h} \rightarrow \infty</math>.

== What seismology can reveal ==

The oscillations that have been successfully utilized for seismology are essentially adiabatic. Their dynamics is therefore the action of pressure forces <math>p</math> (plus putative Maxwell stresses) against matter with inertia density <math>\rho</math>, which itself depends upon the relation between them under adiabatic change, usually quantified via the (first) adiabatic exponent <math>\gamma_1</math>. The equilibrium values of the variables <math>p</math> and <math>\rho</math> (together with the dynamically small angular velocity <math>\Omega</math> and magnetic field <math>\rm B</math>) are related by the constraint of hydrostatic support, which depends upon the total mass <math>M</math> and radius <math>R</math> of the Sun. Evidently, the oscillation frequencies <math>\omega</math> depend only on the seismic variables <math>\rho(p,\Omega,\rm B)</math>, <math>\gamma_1</math>, <math>\Omega</math> and <math>\rm B</math>, or any independent set of functions of them. Consequently it is only about these variables that information can be derived directly. The square of the adiabatic sound speed, <math>c^2 = \gamma_1 p/\rho</math>, is such commonly adopted function, because that is the quantity upon which acoustic propagation principally depends.<ref name = "learned">{{Citation | last1 = Gough | first1 = D.O. | s2cid = 119291920 | title = What have we learned from helioseismology, what have we really learned, and what do we aspire to learn? | journal = Solar Physics | volume = 287 | pages = 9–41 | year = 2003 | issue = 1–2 | doi = 10.1007/s11207-012-0099-1 | arxiv = 1210.0820 }}</ref> Properties of other, non-seismic, quantities, such as helium abundance,<ref>{{Citation | last1 = Kosovichev | first1 = A.G. | last2 = Christensen-Dalsgaard | first2 = J. | last3 = Däeppen | first3 = W. | last4 = Dziembowski | first4 = W.A. | last5 = Gough | first5 = D.O. | last6 = Thompson | first6 = M.J.| journal = Mon. Not. R. Astron. Soc. | volume = 259 | pages = 536–558 | year = 1992 | title = Sources of uncertainty in direct seismological measurements of the solar helium abundance | issue = 3 | doi = 10.1093/mnras/259.3.536 | bibcode = 1992MNRAS.259..536K | doi-access = free | url = http://cds.cern.ch/record/235661/files/CM-P00068017.pdf }}</ref> <math>Y</math>, or main-sequence age<ref>{{Citation | last1 = Houdek | first1 = G. | last2 = Gough | first2 = D.O. | journal = Mon. Not. R. Astron. Soc. | volume = 418 | pages = 1217–1230 | title = On the seismic age and heavy-element abundance of the Sun | doi = 10.1111/j.1365-2966.2011.19572.x | doi-access = free | year = 2011 | issue = 2 | arxiv = 1108.0802 | bibcode = 2011MNRAS.418.1217H }}</ref> <math>t_\odot</math>, can be inferred only by supplementation with additional assumptions, which renders the outcome more uncertain.

== Data analysis ==

=== Global helioseismology ===
[[File:Sun combined power spectrum loglog.png|thumb|Power spectrum of the Sun using data from instruments aboard the [[Solar and Heliospheric Observatory]] on double-logarithmic axes. The three passbands of the VIRGO/SPM instrument show nearly the same power spectrum. The line-of-sight velocity observations from GOLF are less sensitive to the red noise produced by [[granulation (solar physics)|granulation]]. All the datasets clearly show the oscillation modes around 3mHz.]]
[[File:Sun combined power spectrum modes around max power.png|thumb|Power spectrum of the Sun around where the modes have maximum power, using data from the GOLF and VIRGO/SPM instruments aboard the Solar and Heliospheric Observatory. The low-degree modes (l<4) show a clear comb-like pattern with a regular spacing.]]
[[File:MDI medium angular degree power spectrum.png|thumb|Power spectrum of medium angular degree (<math>0\leq\ell<300</math>) solar oscillations, computed for 144 days of data from the MDI instrument aboard [[Solar and Heliospheric Observatory|SOHO]].<ref>{{Citation | last1 = Rhodes | first1 = Jr. E. J. | last2 = Kosovichev | first2 = A. G. | last3 = Schou | first3 = J.| s2cid = 51790986 |display-authors=etal | title = Measurements of Frequencies of Solar Oscillations from the MDI Medium-l Program | year = 1997 | journal = Solar Physics | volume = 175 | issue = 2 | page = 287| bibcode = 1997SoPh..175..287R|doi = 10.1023/A:1004963425123 }}</ref> The colour scale is logarithmic and saturated at one hundredth the maximum power in the signal, to make the modes more visible. The low-frequency region is dominated by the signal of granulation. As the angular degree increases, the individual mode frequencies converge onto clear ridges, each corresponding to a sequence of low-order modes.]]

The chief tool for analysing the raw seismic data is the [[Fourier transform]]. To good approximation, each mode is a damped harmonic oscillator, for which the power as a function of frequency is a [[Lorentz function]]. Spatially resolved data are usually projected onto desired spherical harmonics to obtain time series which are then Fourier transformed. Helioseismologists typically combine the resulting one-dimensional power spectra into a two-dimensional spectrum.

The lower frequency range of the oscillations is dominated by the variations caused by [[granulation (solar physics)|granulation]]. This must first be filtered out before (or at the same time that) the modes are analysed. Granular flows at the solar surface are mostly horizontal, from the centres of the rising granules to the narrow downdrafts between them. Relative to the oscillations, granulation produces a stronger signal in intensity than line-of-sight velocity, so the latter is preferred for helioseismic observatories.

=== Local helioseismology ===

Local helioseismology—a term coined by Charles Lindsey, Doug Braun and Stuart Jefferies in 1993<ref>{{cite book | author1=Lindsey, C. | author2=Braun, D.C. | author3=Jefferies, S.M. | title= "Local Helioseismology of Subsurface Structure" in "GONG 1992. Seismic Investigation of the Sun and Stars" | journal= GONG 1992. Seismic Investigation of the Sun and Stars. Proceedings of a Conference Held in Boulder | date= January 1993 | series= Astronomical Society of the Pacific Conference Series | volume= 42 | editor= T.M. Brown | pages= 81–84 |isbn=978-0-937707-61-6 | bibcode= 1993ASPC...42...81L}}</ref>—employs several different analysis methods to make inferences from the observational data.<ref name="gb2005"/>

* The '''Fourier–Hankel spectral method''' was originally used to search for wave absorption by sunspots.<ref name=Braun1987>{{cite journal | author1=Braun, D.C. | author2=Duvall Jr., T.L. | author3=Labonte, B.J. |title= Acoustic absorption by sunspots | journal= The Astrophysical Journal | date= August 1987 | volume= 319 | pages= L27–L31 | doi= 10.1086/184949 | bibcode= 1987ApJ...319L..27B}}</ref>
* '''Ring-diagram analysis''', first introduced by Frank Hill,<ref>{{cite journal | author = Hill, F. | title = Rings and trumpets - Three-dimensional power spectra of solar oscillations | journal = Astrophysical Journal | date = October 1988 | volume = 333 | pages = 996–1013 | doi = 10.1086/166807 | bibcode = 1988ApJ...333..996H}}</ref> is used to infer the speed and direction of horizontal flows below the solar surface by observing the Doppler shifts of ambient acoustic waves from power spectra of solar oscillations computed over patches of the solar surface (typically 15° × 15°). Thus, ring-diagram analysis is a generalization of global helioseismology applied to local areas on the Sun (as opposed to half of the Sun). For example, the sound speed and [[adiabatic index]] can be compared within magnetically active and inactive (quiet Sun) regions.<ref>{{cite journal |author1=Basu, S. |author2=Antia, H.M. |author3=Bogart, R.S. |title= Ring-Diagram Analysis of the Structure of Solar Active Regions |journal= The Astrophysical Journal |date= August 2004 |volume= 610 |issue= 2 |pages= 1157–1168 |doi= 10.1086/421843 |bibcode= 2004ApJ...610.1157B|doi-access= free }}</ref>
*'''Time-distance helioseismology'''<ref>{{cite journal |author1=Duvall Jr., T.L. |author2=Jefferies, S.M. |author3=Harvey, J.W. |author4=Pomerantz, M.A. |s2cid=4244835 |title= Time-distance helioseismology |journal= Nature |date= April 1993 |volume= 362 |issue= 6419 |pages= 430–432 |doi= 10.1038/362430a0 |bibcode= 1993Natur.362..430D|hdl=2060/20110005678 |hdl-access= free }}</ref> aims to measure and interpret the travel times of solar waves between any two locations on the solar surface. Inhomogeneities near the ray path connecting the two locations perturb the travel time between those two points. An inverse problem must then be solved to infer the local structure and dynamics of the solar interior.<ref name=Jensen2003>{{Citation | last1 = Jensen | first1 = J. M. | title = Time-distance: what does it tell us? | journal = Gong+ 2002. Local and Global Helioseismology: The Present and Future | year = 2003 | volume = 517 | page = 61| bibcode = 2003ESASP.517...61J}}</ref>
*'''Helioseismic holography''', introduced in detail by Charles Lindsey and Doug Braun for the purpose of far-side (magnetic) imaging,<ref>{{Citation | last1 = Braun | first1 = D. C. | last2 = Lindsey | first2 = C. | title = Seismic Imaging of the Far Hemisphere of the Sun | year = 2001 | journal = Astrophysical Journal Letters | volume = 560 | issue = 2 | pages = L189| bibcode = 2001ApJ...560L.189B| doi = 10.1086/324323 | doi-access = free }}</ref> is a special case of phase-sensitive holography. The idea is to use the wavefield on the visible disk to learn about [[active region]]s on the far side of the Sun. The basic idea in helioseismic holography is that the wavefield, e.g., the line-of-sight Doppler velocity observed at the solar surface, can be used to make an estimate of the wavefield at any location in the solar interior at any instant in time. In this sense, holography is much like [[seismic migration]], a technique in geophysics that has been in use since the 1940s. As another example, this technique has been used to give a seismic image of a solar flare.<ref>{{cite journal |author1=Donea, A.-C. |author2=Braun, D.C. |author3=Lindsey, C. |title= Seismic Images of a Solar Flare |journal= The Astrophysical Journal |date= March 1999 |volume= 513 |issue= 2 |pages= L143–L146 |doi= 10.1086/311915 |bibcode= 1999ApJ...513L.143D|doi-access= free }}</ref>
*In '''direct modelling''', the idea is to estimate subsurface flows from direct inversion of the frequency-wavenumber correlations seen in the wavefield in the Fourier domain. Woodard<ref name=Woodard2002>{{cite journal
|author= Woodard, M. F. |title= Solar Subsurface Flow Inferred Directly from Frequency-Wavenumber Correlations in the Seismic Velocity Field |journal= The Astrophysical Journal |date= January 2002 |volume= 565 |issue= 1 |pages= 634–639 |doi= 10.1086/324546 |bibcode= 2002ApJ...565..634W|citeseerx= 10.1.1.513.1704 |s2cid= 122970114 }}</ref> demonstrated the ability of the technique to recover near-surface flows the f modes.

== Inversion ==

=== Introduction ===

The Sun's oscillation modes represent a discrete set of observations that are sensitive to its continuous structure. This allows scientists to formulate [[inverse problem]]s for the Sun's interior structure and dynamics. Given a reference model of the Sun, the differences between its mode frequencies and those of the Sun, if small, are weighted averages of the differences between the Sun's structure and that of the reference model. The frequency differences can then be used to infer those structural differences. The weighting functions of these averages are known as ''kernels''.

=== Structure ===

The first inversions of the Sun's structure were made using Duvall's law<ref>{{Citation | last1 = Christensen-Dalsgaard | first1 = J. | last2 = Duvall | first2 = Jr. T. L. | last3 = Gough | first3 = D. O. | last4 = Harvey | first4 = J. W. | last5 = Rhodes | first5 = Jr. E. J. | s2cid = 4338576 | title = Speed of sound in the solar interior | year = 1985 | journal = Nature | volume = 315 | issue = 6018 | page = 378| bibcode = 1985Natur.315..378C| doi = 10.1038/315378a0 }}</ref> and later using Duvall's law linearized about a reference solar model.<ref>{{Citation | last1 = Christensen-Dalsgaard | first1 = J. | last2 = Thompson | first2 = M. J. | last3 = Gough | first3 = D. O. | title = Differential asymptotic sound-speed inversions | year = 1989 | journal = MNRAS | volume = 238 | issue = 2 | pages = 481–502| bibcode = 1989MNRAS.238..481C| doi = 10.1093/mnras/238.2.481 | doi-access = free }}</ref> These results were subsequently supplemented by analyses that linearize the full set of equations describing the stellar oscillations about a theoretical reference model <ref name = "snowmass" /><ref>{{Citation | last1 = Dziembowski | first1 = W.A. | last2 = Pamyatnykh | first2 = A.A. | last3 = Sienkiewicz | first3 = R. | journal = Mon. Not. R. Astron. Soc. | volume = 244 | pages = 542–550 | year = 1990 | title = Solar model from helioseismology and the neutrino flux problem | bibcode = 1990MNRAS.244..542D }}</ref><ref>{{Citation | last1 = Antia | first1 = H. M. | last2 = Basu | first2 = S. | title = Nonasymptotic helioseismic inversion for solar structure. | year = 1994 | journal = Astronomy & Astrophysics Supplement Series | volume = 107 | page = 421| bibcode = 1994A&AS..107..421A}}</ref> and are now a standard way to invert frequency data.<ref>{{Citation | last1 = Gough | first1 = D.O. | last2 = Thompson | first2 = M.J. | chapter= The inversion problem | title= Solar interior and atmosphere |editor1=A. N. Cox |editor2=W. C. Livingston |editor3=M. S. Matthews |publisher=University of Arizona Press |location=Tucson | pages = 519–561 | year = 1991 | bibcode = 1991sia..book..519G }}</ref><ref>{{Citation | last1 = Basu | first1 = S. | s2cid = 118486913 | title = Global seismology of the Sun | year = 2016 | journal = Living Reviews in Solar Physics | volume = 13 | issue = 1 | article-number = 2| arxiv = 1606.07071 | bibcode = 2016LRSP...13....2B| doi = 10.1007/s41116-016-0003-4 }}</ref> The inversions demonstrated differences in solar models that were greatly reduced by implementing ''gravitational settling'': the gradual separation of heavier elements towards the solar centre (and lighter elements to the surface to replace them).<ref>{{Citation | last1 = Cox | first1 = A. N. | last2 = Guzik | first2 = J. A. | last3 = Kidman | first3 = R. B. | title = Oscillations of solar models with internal element diffusion | year = 1989 | journal = Astrophysical Journal | volume = 342 | page = 1187| bibcode = 1989ApJ...342.1187C| doi = 10.1086/167675 | osti = 5776275 | s2cid = 122535514 | url = https://digital.library.unt.edu/ark:/67531/metadc1103544/ }}</ref><ref>{{Citation | last1 = Christensen-Dalsgaard | first1 = J. | last2 = Proffitt | first2 = C. R. | last3 = Thompson | first3 = M. J. | title = Effects of diffusion on solar models and their oscillation frequencies | year = 1993 | journal = Astrophysical Journal Letters | volume = 403 | pages = L75| bibcode = 1993ApJ...403L..75C| doi = 10.1086/186725 | url = https://cds.cern.ch/record/243236/files/CM-P00068027.pdf }}</ref>

=== Rotation ===
[[File:HMI 2D solar rotation profile.png|thumb|The internal rotation profile of the Sun inferred using data from the [[Helioseismic and Magnetic Imager]] aboard the [[Solar Dynamics Observatory]]. The inner radius has been truncated where the measurements are less certain than 1%, which happens around 3/4 of the way to the core. The dashed line indicates the base of the solar convection zone, which happens to coincide with the boundary at which the rotation profile changes, known as the tachocline.]]

If the Sun were perfectly spherical, the modes with different azimuthal orders ''m'' would have the same frequencies. Rotation, however, breaks this degeneracy, and the modes frequencies differ by ''rotational splittings'' that are weighted-averages of the angular velocity through the Sun. Different modes are sensitive to different parts of the Sun and, given enough data, these differences can be used to infer the rotation rate throughout the Sun.<ref>{{Citation | last1 = Thompson | first1 = M. J. | last2 = Christensen-Dalsgaard | first2 = J. | last3 = Miesch | first3 = M. S. | last4 = Toomre | first4 = J. | s2cid = 123622875 | title = The Internal Rotation of the Sun | year = 2003 | journal = Annual Review of Astronomy & Astrophysics | volume = 41 | pages = 599–643| bibcode = 2003ARA&A..41..599T| doi = 10.1146/annurev.astro.41.011802.094848 }}</ref> For example, if the Sun were rotating uniformly throughout, all the p modes would be split by approximately the same amount. Actually, the angular velocity is not uniform, as can be seen at the surface, where the equator rotates faster than the poles.<ref>{{Citation | last1 = Beck | first1 = J. G. | s2cid = 118030329 | title = A comparison of differential rotation measurements - (Invited Review) | year = 2000 | journal = Solar Physics | volume = 191 | issue = 1 | pages = 47–70| bibcode = 2000SoPh..191...47B| doi = 10.1023/A:1005226402796 }}</ref> The Sun rotates slowly enough that a spherical, non-rotating model is close enough to reality for deriving the rotational kernels.

Helioseismology has shown that the Sun has a rotation profile with several features:<ref>{{Citation | last1 = Howe | first1 = R. | s2cid = 10532243 | title = Solar Interior Rotation and its Variation | year = 2009 | journal = Living Reviews in Solar Physics | volume = 6 | issue = 1 | page = 1| arxiv = 0902.2406 | bibcode = 2009LRSP....6....1H| doi = 10.12942/lrsp-2009-1 | doi-access = free }}</ref>
* a rigidly-rotating radiative (i.e. non-convective) zone, though the rotation rate of the inner core is not well known;
* a thin shear layer, known as the ''tachocline'', which separates the rigidly-rotating interior and the differentially-rotating convective envelope;
* a convective envelope in which the rotation rate varies both with depth and latitude; and
* a final shear layer just beneath the surface, in which the rotation rate slows down towards the surface.

== Relationship to other fields ==

=== Geoseismology ===

{{Main|Seismology}}

Helioseismology was born from analogy with [[seismology|geoseismology]] but several important differences remain. First, the Sun lacks a solid surface and therefore cannot support [[shear wave]]s. From the data analysis perspective, global helioseismology differs from geoseismology by studying only normal modes. Local helioseismology is thus somewhat closer in spirit to geoseismology in the sense that it studies the complete wavefield.

=== Asteroseismology ===

{{Main|Asteroseismology}}

Because the Sun is a star, helioseismology is closely related to the study of oscillations in other stars, known as [[asteroseismology]]. Helioseismology is most closely related to the study of stars whose oscillations are also driven and damped by their outer convection zones, known as [[solar-like oscillations|solar-like oscillators]], but the underlying theory is broadly the same for other classes of variable star.

The principal difference is that oscillations in distant stars cannot be resolved. Because the brighter and darker sectors of the spherical harmonic cancel out, this restricts asteroseismology almost entirely to the study of low degree modes (angular degree <math>\ell\leq3</math>). This makes inversion much more difficult but upper limits can still be achieved by making more restrictive assumptions.

== History ==

Solar oscillations were first observed in the early 1960s<ref>{{Citation | last1 = Leighton | first1 = R. B. | last2 = Noyes | first2 = R. W. | last3 = Simon | first3 = G. W. | title = Velocity Fields in the Solar Atmosphere. I. Preliminary Report. | year = 1962 | journal = Astrophysical Journal | volume = 135 | page = 474| bibcode = 1962ApJ...135..474L| doi = 10.1086/147285 }}</ref><ref>{{Citation | last1 = Evans | first1 = J. W. | last2 = Michard | first2 = R. | title = Observational Study of Macroscopic Inhomogeneities in the Solar Atmosphere. III. Vertical Oscillatory Motions in the Solar Photosphere. | year = 1962 | journal = Astrophysical Journal | volume = 136 | page = 493| bibcode = 1962ApJ...136..493E| doi = 10.1086/147403 | doi-access = free }}</ref> as a quasi-periodic intensity and line-of-sight velocity variation with a period of about 5 minutes. Scientists gradually realized that the oscillations might be global modes of the Sun and predicted that the modes would form clear ridges in two-dimensional power spectra.<ref>{{Citation | last1 = Leibacher | first1 = J. W. | last2 = Stein | first2 = R. F. | title = A New Description of the Solar Five-Minute Oscillation | year = 1971 | journal = Astrophysical Letters | volume = 7 | page = 191| bibcode = 1971ApL.....7..191L}}</ref><ref>{{Citation | last1 = Ulrich | first1 = R. K. | s2cid = 17225920 | title = The Five-Minute Oscillations on the Solar Surface | year = 1970 | journal = Astrophysical Journal | volume = 162 | page = 993| bibcode = 1970ApJ...162..993U| doi = 10.1086/150731 }}</ref> The ridges were subsequently confirmed in observations of high-degree modes in the mid 1970s,<ref>{{Citation | last1 = Deubner | first1 = F.-L. | title = Observations of low wavenumber nonradial eigenmodes of the sun | year = 1975 | journal = Astronomy and Astrophysics | volume = 44 | issue = 2 | page = 371| bibcode = 1975A&A....44..371D}}</ref><ref name = "ejrrkugws">{{Citation | last1 = Rhodes | first1 = Jr. E. J. | last2 = Ulrich | first2 = R. K. | last3 = Simon | first3 = G. W. | s2cid = 115143527 | title = Observations of nonradial p-mode oscillations on the sun | year = 1977 | journal = Astrophysical Journal | volume = 218 | page = 901| bibcode = 1977ApJ...218..901R| doi = 10.1086/155745 }}</ref> and mode multiplets of different radial orders were distinguished in whole-disc observations.<ref name = "Grecsouthpole" /><ref>{{Citation | last1 = Claverie | first1 = A. | last2 = Isaak | first2 = G. R. | last3 = McLeod | first3 = C. P. | last4 = van | first4 = der Raay H. B. | last5 = Cortes | first5 = T. R. | s2cid = 4342247 | title = Solar structure from global studies of the 5-minute oscillation | year = 1979 | journal = Nature | volume = 282 | issue = 5739 | pages = 591–594| bibcode = 1979Natur.282..591C| doi = 10.1038/282591a0 }}</ref> At a similar time, [[Jørgen Christensen-Dalsgaard]] and [[Douglas Gough]] suggested the potential of using individual mode frequencies to infer the interior structure of the Sun.<ref>{{Citation | last1 = Christensen-Dalsgaard | first1 = J. | last2 = Gough | first2 = D. O. | s2cid = 10540902 | title = Towards a heliological inverse problem | year = 1976 | journal = Nature | volume = 259 | issue = 5539 | page = 89| bibcode = 1976Natur.259...89C| doi = 10.1038/259089a0 }}</ref> They calibrated solar models against the low-degree data<ref>{{Citation | last1 = Christensen-Dalsgaard | first1 = J. | last2 = Gough | first2 = D. O. | title = Comparison of the observed solar whole-disk oscillation frequencies with the predictions of a sequence of solar models | journal = Astron. Astrophys. | volume = 104 | pages = 173–176 | year = 1981 | issue = 2 | bibcode = 1981A&A...104..173C }}</ref> finding two similarly good fits, one with low <math>Y</math> and a corresponding low neutrino production rate <math>L_\nu</math>, the other with higher <math>Y</math> and <math>L_\nu</math>; earlier envelope calibrations against high-degree frequencies<ref>{{Citation | last1 = Gough | first1 = D.O. | title = Random remarks on solar hydrodynamics | journal = Proc. IAU Colloq. 36 | pages = 3–36 | year = 1977 | bibcode = 1977ebhs.coll....3G }}</ref><ref name = "ejrrku">{{Citation | last1 = Rhodes | first1 = Jr. E. J. | last2 = Ulrich | first2 = R. K. | title = The sensitivity of nonradial p mode eigenfrequencies to solar envelope structure | year = 1977 | journal = Astrophysical Journal | volume = 218 | pages = 521–529| bibcode = 1977ApJ...218..521U | doi = 10.1086/155705 | doi-access = free }}</ref> preferred the latter, but the results were not wholly convincing. It was not until Tom Duvall and Jack Harvey<ref name="duvall_southpole1983" /> connected the two extreme data sets by measuring modes of intermediate degree to establish the quantum numbers associated with the earlier observations that the higher-<math>Y</math> model was established, thereby suggesting at that early stage that the resolution of the neutrino problem must lie in nuclear or particle physics.

New methods of inversion developed in the 1980s, allowing researchers to infer the profiles sound speed and, less accurately, density throughout most of the Sun, corroborating the conclusion that residual errors in the inference of the solar structure is not the cause of the neutrino problem. Towards the end of the decade, observations also began to show that the oscillation mode frequencies vary with the [[solar cycle|Sun's magnetic activity cycle]].<ref>{{Citation | last1 = Libbrecht | first1 = K. G. | last2 = Woodard | first2 = M. F. | s2cid = 4305062 | title = Solar-cycle effects on solar oscillation frequencies | year = 1990 | journal = Nature | volume = 345 | issue = 6278 | page = 779| bibcode = 1990Natur.345..779L| doi = 10.1038/345779a0 }}</ref>

To overcome the problem of not being able to observe the Sun at night, several groups had begun to assemble networks of telescopes (e.g. the [[Birmingham Solar Oscillations Network]], or BiSON,<ref>{{Citation | last1 = Aindow | first1 = A. | last2 = Elsworth | first2 = Y. P. | last3 = Isaak | first3 = G. R. | last4 = McLeod | first4 = C. P. | last5 = New | first5 = R. | last6 = Vanderraay | first6 = H. B. | title = The current status of the Birmingham solar seismology network | journal = Seismology of the Sun and Sun-Like Stars | year = 1988 | volume = 286 | page = 157| bibcode = 1988ESASP.286..157A}}</ref><ref>{{Citation | last1 = Chaplin | first1 = W. J. | last2 = Elsworth | first2 = Y. | last3 = Howe | first3 = R. | last4 = Isaak | first4 = G. R. | last5 = McLeod | first5 = C. P. | last6 = Miller | first6 = B. A. | last7 = van | first7 = der Raay H. B. | last8 = Wheeler | first8 = S. J. | last9 = New | first9 = R. | title = BiSON Performance | year = 1996 | journal = Solar Physics | volume = 168 | issue = 1 | page = 1| bibcode = 1996SoPh..168....1C| doi = 10.1007/BF00145821 | s2cid = 189828557 }}</ref> and the [[Global Oscillation Network Group]]<ref>{{Citation | last1 = Harvey | first1 = J. W. | last2 = Hill | first2 = F. | last3 = Kennedy | first3 = J. R. | last4 = Leibacher | first4 = J. W. | last5 = Livingston | first5 = W. C. | title = The Global Oscillation Network Group (GONG) | year = 1988 | journal = Advances in Space Research | volume = 8 | issue = 11 | page = 117| bibcode = 1988AdSpR...8k.117H| doi = 10.1016/0273-1177(88)90304-3 }})</ref>) from which the Sun would always be visible to at least one node. Long, uninterrupted observations brought the field to maturity, and the state of the field was summarized in a 1996 special issue of ''[[Science (journal)|Science magazine]]''.<ref>{{Citation | journal = Science | title = Special Issue: GONG Helioseismology | volume = 272 | issue = 5266 | year = 1996 | url = https://www.science.org/toc/science/272/5266}}</ref> This coincided with the start of normal operations of the [[Solar and Heliospheric Observatory]] (SoHO), which began producing high-quality data for helioseismology.

The subsequent years saw the resolution of the solar neutrino problem, and the long seismic observations began to allow analysis of multiple solar activity cycles.<ref>{{Citation | last1 = Chaplin | first1 = W. J. | last2 = Elsworth | first2 = Y. | last3 = Miller | first3 = B. A. | last4 = Verner | first4 = G. A. | last5 = New | first5 = R. | title = Solar p-Mode Frequencies over Three Solar Cycles | year = 2007 | journal = Astrophysical Journal | volume = 659 | issue = 2 | page = 1749| bibcode = 2007ApJ...659.1749C| doi = 10.1086/512543 | doi-access = free }}</ref> The agreement between standard solar models and helioseismic inversions<ref>{{Citation | last1 = Bahcall | first1 = J. N. | last2 = Pinsonneault | first2 = M. H. | last3 = Basu | first3 = S. | s2cid = 13798091 | title = Solar Models: Current Epoch and Time Dependences Neutrinos and Helioseismological Properties | year = 2001 | journal = Astrophysical Journal | volume = 555 | issue = 2 | pages = 990–1012| arxiv = astro-ph/0010346 | bibcode = 2001ApJ...555..990B| doi = 10.1086/321493 }}</ref> was disrupted by new measurements of the heavy element content of the solar photosphere based on detailed three-dimensional models.<ref>{{Citation | last1 = Asplund | first1 = M. | last2 = Grevesse | first2 = N. | last3 = Sauval | first3 = A. J. | title = The Solar Chemical Composition | journal = Cosmic Abundances as Records of Stellar Evolution and Nucleosynthesis | year = 2005 | volume = 336 | page = 25| bibcode = 2005ASPC..336...25A}}</ref> Though the results later shifted back towards the traditional values used in the 1990s,<ref>{{Citation | last1 = Asplund | first1 = M. | last2 = Grevesse | first2 = N. | last3 = Sauval | first3 = A. J. | last4 = Scott | first4 = P. | s2cid = 17921922 | title = The Chemical Composition of the Sun | year = 2009 | journal = Annual Review of Astronomy & Astrophysics | volume = 47 | issue = 1 | pages = 481–522| arxiv = 0909.0948 | bibcode = 2009ARA&A..47..481A| doi = 10.1146/annurev.astro.46.060407.145222 }}</ref> the new abundances significantly worsened the agreement between the models and helioseismic inversions.<ref>{{Citation | last1 = Bahcall | first1 = J. N. | last2 = Basu | first2 = S. | last3 = Pinsonneault | first3 = M. | last4 = Serenelli | first4 = A. M. | s2cid = 2412268 | title = Helioseismological Implications of Recent Solar Abundance Determinations | year = 2005 | journal = Astrophysical Journal | volume = 618 | issue = 2 | pages = 1049–1056| arxiv = astro-ph/0407060 | bibcode = 2005ApJ...618.1049B| doi = 10.1086/426070 }}</ref> The cause of the discrepancy remains unsolved<ref name = "learned"/> and is known as the ''solar abundance problem''.

Space-based observations by SoHO have continued and SoHO was joined in 2010 by the [[Solar Dynamics Observatory]] (SDO), which has also been monitoring the Sun continuously since its operations began. In addition, ground-based networks (notably BiSON and GONG) continue to operate, providing nearly continuous data from the ground too.

==See also==
{{colbegin}}
*[[160-minute solar cycle]]
*[[Coronal seismology]]
*[[Differential rotation]]
*[[Diskoseismology]]
*[[Frequency separation]]
*[[Magnetogravity wave]]
*[[Moreton wave]]
*[[Solar neutrino problem]]
*[[Solar tower (astronomy)]]
*[[Stellar rotation]]
{{colend}}

==References==
{{Reflist|30em}}

==External links==
{{Commons category|Helioseismology}}
*[https://web.archive.org/web/20110719120639/http://ast.phys.au.dk/helio_outreach/english/ Non-technical description of helio- and asteroseismology] retrieved November 2009
*{{cite journal | last1 = Gough | first1 = D.O. | s2cid = 195335212 | title = Solar Neutrino Production | journal = Annales Henri Poincaré | volume = 4 | issue = S1 | pages = 303–317 | year = 2003 | bibcode = 2003AnHP....4..303G | doi = 10.1007/s00023-003-0924-z | doi-access = free }}
*{{cite journal | last1 = Gizon | first1 = Laurent | last2 = Birch | first2 = Aaron C. | year = 2005| title = Local Helioseismology | journal = Living Rev. Sol. Phys. | volume = 2| issue = 1| page = 6| doi = 10.12942/lrsp-2005-6 | bibcode = 2005LRSP....2....6G | doi-access = free }}
*[https://www.nsf.gov/news/news_summ.jsp?cntn_id=105844&org=olpa&from=news Scientists Issue Unprecedented Forecast of Next Sunspot Cycle] National Science Foundation press release, March 6, 2006
*{{cite journal | last1 = Miesch | first1 = Mark S. | year = 2005| title = Large-Scale Dynamics of the Convection Zone and Tachocline | journal = Living Rev. Sol. Phys. | volume = 2| issue = 1| page = 1| doi = 10.12942/lrsp-2005-1 | bibcode = 2005LRSP....2....1M | doi-access = free}}
*[https://web.archive.org/web/20080919115719/http://www.helas-eu.org/ European Helio- and Asteroseismology Network (HELAS)]
*[http://soi.stanford.edu/data/full_farside/ Farside and Earthside images of the Sun]
*[http://solarphysics.livingreviews.org/ Living Reviews in Solar Physics] {{Webarchive|url=https://web.archive.org/web/20100929001133/http://solarphysics.livingreviews.org/ |date=2010-09-29 }}
*[http://www.mps.mpg.de/helioseismology-asteroseismology/research Helioseismology and Asteroseismology] at [[Max Planck Institute for Solar System Research|MPS]]

===Satellite instruments===
*[http://www.ias.u-psud.fr/virgo VIRGO]
*[http://soi.stanford.edu SOI/MDI]
*[http://hmi.stanford.edu/ SDO/HMI]
*[https://web.archive.org/web/20120726082944/http://sunland.gsfc.nasa.gov/smex/trace/ TRACE]

===Ground-based instruments===
*[http://bison.ph.bham.ac.uk/ BiSON]
*Mark-1
*[http://gong.nso.edu/ GONG]
*[http://physics.usc.edu/solar HiDHN]

== Further reading ==

*{{cite web
| last = Christensen-Dalsgaard
| first = Jørgen
| title = Lecture notes on stellar oscillations
| url = http://astro.phys.au.dk/~jcd/oscilnotes/
| access-date = 5 June 2015
| archive-date = 1 July 2018
| archive-url = https://web.archive.org/web/20180701022710/http://astro.phys.au.dk/~jcd/oscilnotes/
| url-status = dead
}}
*{{cite book
| last1 = Pijpers | first1 = Frank P.
| title = Methods in Helio- and Asteroseismology
| publisher = Imperial College Press
| date = 2006
| location = London
| isbn = 978-1-8609-4755-1
}}

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[[Category:Fields of seismology]]
[[Category:Sun|Seismology]]
[[Category:Stellar phenomena]]
[[Category:Asteroseismology]]
[[Category:Concepts in stellar astronomy]]

European-Mediterranean Seismological Centre

2025-08-25T16:12:21Z

OpenDEM 1: 1 revision imported from :wikipedia:en:European-Mediterranean_Seismological_Centre

{{more footnotes|date=April 2014}}
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| location = [[Bruyères-le-Châtel]], [[Essonne]], [[France]]
| employees = 10 (2016)
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| region = [[Île-de-France]]
| services = Rapid Earthquake information
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| fields = [[Seismology]]
| membership = 85
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| website = {{URL|https://www.emsc-csem.org/}}
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}}

The '''European-Mediterranean Seismological Centre''' ('''EMSC'''; {{langx|fr|Centre Sismologique Euro-Méditerranéen}}, {{lang|fr|CSEM}}) is an international, [[Non-governmental organization|non-governmental]] and [[not-for-profit organisation]].

The European-Mediterranean region is prone to destructive earthquakes.<ref>{{Cite web|last=gisetc|title=European Earthquake Risk Concentrated Around the Mediterranean {{!}} GISetc|url=https://www.gisetc.com/european-earthquake-risk-concentrated-around-the-mediterranean/|access-date=2020-12-23|language=en}}</ref> When an [[earthquake]] occurs, a scientific organisation is needed to determine, as quickly as possible, the characteristics of the seismic event. The European-Mediterranean Seismological Centre (EMSC) receives seismological data from more than 65 national seismological agencies, mostly in the Euro-Mediterranean region. The most relevant earthquake parameters, such as the [[earthquake location]] and the [[earthquake magnitude]], and the shaking felt by the population are available within one hour from the earthquake onset.

== History ==
The European-Mediterranean Seismological Centre (EMSC) is a [[not-for-profit organisation]] with 84 member institutes from 55 different countries. The centre was established in 1975 under the request of the [[European Seismological Commission (ESC)]].

The EMSC became operational on 1 January 1975, at the [[Institut de Physique du Globe de Strasbourg]]. It received its final statute in 1983. In 1987, the EMSC was appointed by the [[Council of Europe]] as the main organisation to provide the [[European Alert System]] under the Open Partial Agreement (OPA) on Major Hazards.

In 1993, the EMSC statute and organisation were amended. Its headquarters moved to the Laboratoire de Détection et de Géophysique (LDG) within the Département Analyse, Surveillance, Environnement (DASE) of the French Atomic Energy Commission (CEA), in Bruyères-le-Châtel (Essonne, France).

As an international, non-governmental and non-profit organisation, the EMSC also focuses on promoting seismological research within and beyond its community. Hence, the EMSC is involved in many European (FP7 and H2020) projects:

FP7 projects:
* [https://web.archive.org/web/20161013093730/http://www.nera-eu.org/ NERA]
* [http://www.verce.eu VERCE]
* [http://marsite.eu/ MARsite]
* [http://www.reaktproject.eu/ REAKT]
[[Framework Programmes for Research and Technological Development#Horizon 2020|H2020 projects]]:
* [https://www.epos-ip.org/ EPOS-IP] {{Webarchive|url=https://web.archive.org/web/20160310122329/https://www.epos-ip.org/ |date=2016-03-10 }}
* [https://www.improverproject.eu/ IMPROVER]
* [http://www.carismand.eu/ CARISMAND]
* [http://www.envriplus.eu/ ENVRIplus]
* [http://arise-project.eu/ ARISE2]
Other projects:
* [http://www.projet-sigma.com/organisation.html SIGMA] {{Webarchive|url=https://web.archive.org/web/20160808064600/http://www.projet-sigma.com/organisation.html |date=2016-08-08 }}
* [http://international.usgs.gov/projects/prjrelemr.htm RELEMR]
* [http://aristotle.ingv.it/ ARISTOTLE]

== Objectives and activities ==
The main scientific objectives of the EMSC are:
* To establish and operate a system for rapid determination of the European and Mediterranean earthquake epicentres (location of major earthquakes within a delay of approximately one hour). EMSC, acting as the central authority, is responsible for transmitting these results immediately to the appropriate international authorities and to the members in order to meet the needs of protection of society, scientific progress and general information.
* To determine the main source parameters (epicentre coordinates, depth, magnitude, [[focal mechanism]]s, etc) of major seismic events located within the European-Mediterranean region, and to dispatch widely the corresponding results.
* To collect the data and make them available to other international, regional or national data centres such as the International Seismological Centre (ISC), the United States National Earthquake Information Center (NEIC), etc.
* To encourage scientific cooperation among European and Mediterranean countries in the field of earthquake research, and to develop studies of general interest such as: epicentre location methods, construction of local and regional travel-time tables, magnitude determination, etc.
* To promote seismological data exchange between laboratories in the European-Mediterranean area.
* To afford detailed studies of specific events.
* To build a European seismological data bank.
* To improve the observational systems in the European-Mediterranean region through a critical examination of the seismological coverage, and suggest methods in order to improve the quality of observations and their transmission to EMSC.

== Specific approaches ==
=== Flashsourcing ===
EMSC has developed a new approach based on internet traffic analysis: when an earthquake occurs, witnesses rush on the [https://www.emsc-csem.org/#2 EMSC website] to look for further explanation of the event. Therefore, they create a surge in the website traffic which can indicate that an earthquake just occurred, even before receiving data provided by national seismological institutes. By identifying the geographical origin of the website's visitors, the area where the earthquake was felt is mapped within a couple of minutes of its occurrence. This technique is named flashsourcing.<ref>{{Cite journal|last=Bossu|first=Rémy|last2=Gilles|first2=Sébastien|last3=Mazet-Roux|first3=Gilles|last4=Roussel|first4=Fréderic|last5=Frobert|first5=Laurent|last6=Kamb|first6=Linus|date=2012-01-14|title=Flash sourcing, or rapid detection and characterization of earthquake effects through website traffic analysis|url=https://www.annalsofgeophysics.eu/index.php/annals/article/view/5265|journal=Annals of Geophysics|language=en|volume=54|issue=6|doi=10.4401/ag-5265|issn=2037-416X|doi-access=free}}</ref>

=== Citizen seismology ===
Citizens are a primary source of information in the real-time earthquake detections. EMSC involves them in earthquake response by collecting in-situ information (e.g., questionnaires, pictures, videos) on the earthquake impact directly from the earthquake eyewitnesses. Consequently, by involving the citizens in the response, the EMSC paves the way for an efficient strategy to raise seismic risk awareness.<ref>{{Cite web|title=LastQuake: Felt an earthquake? Share your testimony and become a citizen seismologist!|url=https://m.emsc.eu/|access-date=2020-12-23|website=m.emsc.eu}}</ref>

== References ==
{{Reflist}}

* [https://www.science.org/doi/abs/10.1126/science.1214650?sid=bcc3535e-2686-4700-bcac-7e9f2108b987] Transforming Earthquake Detection?
* [https://www.wilsoncenter.org/publication/transforming-earthquake-detection-and-science-through-citizen-seismology] Transforming Earthquake Detection and Science through Citizen Seismology

== External links ==
* {{official website|https://www.emsc-csem.org/}}
* [https://www.citizenseismology.eu/ Citizen Seismology]

{{Authority control}}

[[Category:Earthquake and seismic risk mitigation]]
[[Category:Seismological observatories, organisations and projects]]
[[Category:Seismic networks]]
[[Category:Organizations based in Île-de-France]]

Template:Natural disasters

2025-08-25T16:12:20Z

OpenDEM 1: 1 revision imported from :wikipedia:en:Template:Natural_disasters

{{Navbox
|name = Natural disasters
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