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[[File:Eq-prob.jpg|thumb|right|250px|[[San Francisco]] Bay earthquake prediction]]

{{complex|date=November 2019}}

[[File:Sanfranciscoearthquake1906.jpg|thumb|250px|Damage from the [[San Francisco]], [[California]] earthquake in 1906]]

[[File:Sanfranciscoearthquake1906.jpg|thumb|250px|Damage from the [[San Francisco]], [[California]] earthquake, sometime in 1906.]]

[[File:EastHanSeismograph.JPG|thumb|Replica of ancient [[seismometer]] with pendulum sensitive to ground tremors. In [[Luoyang]] in 133 AD, it detected an earthquake 400 to 500 km (250 to 310 mi) away]]

An '''earthquake''' (also known as a quake, or tremor) is a violent movement of the rocks in the [[Crust (geology)|Earth's crust]]. Earthquakes are usually quite brief, but may repeat over a long period of time. They are the result of a sudden release of energy in the [[Earth's crust]]. This creates seismic waves, waves of energy that travel through the Earth.  

An '''earthquake''' is the sudden movement of the Earth's [[tectonic plates]], resulting in shaking of the ground. This shaking can result in the damage of various structures such as buildings and further breakdown of the Earth's surface.  

There are [[large]] earthquakes and [[small]] earthquakes. Big earthquakes can take down buildings and cause death and injury. The study of earthquakes is called [[seismology]].<ref name=camilla>{{cite book | last = | first = | authorlink = | coauthors = | title = Earth Science| publisher = Holt, Rinehart Winston| date = 2001| location = Austin, [[Texas]] 78746-6487| pages = | url = | doi = | id = | isbn = 0-03-055667-8}}</ref> Seismology studies the frequency, type and size of earthquakes over a period of time.

The study of earthquakes is called [[seismology]].<ref name="camilla">{{cite book | last = | first = | authorlink = | coauthors = | title = Earth Science| publisher = Holt, Rinehart Winston| date = 2001| location = Austin, [[Texas]] 78746-6487| pages = | url = | doi = | id = | isbn = 0-03-055667-8}}</ref> Earthquakes are usually quite brief, but there may be many over a short time frame. The sudden release of tension in the [[tectonic plates]] sends waves of energy that travel through the Earth. [[Seismology]] studies the cause, frequency, type and size of earthquakes.

When the earth moves offshore in the [[ocean]], it can cause a [[tsunami]]. This can cause just as much death and destruction as an earthquake. [[Landslide]]s can happen, too. This is an important part of the Earth's [[rock cycle]].

There are [[large]] earthquakes and [[small]] earthquakes. Large earthquakes can take down buildings and cause death and injury. Earthquakes are measured using observations from [[seismograph]]s. The magnitude of an earthquake and the intensity of shaking is usually reported on the [[Richter scale]]. The Richter Scale was invented by Charles Francis Richter in 1935. On the scale, 2 is scarcely noticeable, and magnitude 5 (or more) causes damage over a wide area.

Earthquakes are measured using observations from [[seismometer]]s. The magnitude of an earthquake, and the intensity of shaking, is usually reported on the [[Richter scale]]. On the scale, 3 or less is scarcely noticeable, and magnitude 7 (or more) causes damage over a wide area.

An earthquake under the [[ocean]] can cause a [[tsunami]], which can cause just as much destruction as the earthquake itself in mountainous areas. Earthquakes can also cause [[Landslide|landslides]]. Earthquakes are part of the Earth's natural [[rock cycle]].

The impact of an earthquake can be measured by a seismometer. It detects the vibrations caused and it puts these movements on a seismograph. The strength, or magnitude, of an earthquake, is measured using the Richter scale. The Richter scale is numbered 0-9. The largest earthquake ever measured was a 9.5 on the scale a 10 has never been recorded.

 

Scientists cannot predict an earthquake before it happens. But we do know where earthquakes might happen in the future, like close to [[fault (geology)|fault lines]].An earthquake under the ocean can cause a tsunami, this can cause just as much destruction as the earthquake itself.

== History ==

== History ==

The [[Ancient China|ancient Chinese]] used a device that looked like a jar with [[dragon]]s on the top surrounded by frogs with their mouths open. When an earthquake occurred, a ball fitted into each dragon's mouth would drop out of the dragon's mouth into the frog's. The position of the frog which received a ball indicated the direction of the earthquake.

Earthquakes sometimes hit cities and kill hundreds or thousands of people. Most earthquakes happen along the [[Pacific Ring of Fire]] but the biggest ones mostly happen in other places. [[Tectonically]] active places are places where earthquakes or [[volcanic eruption]]s are frequent.

== Causes of earthquakes ==

== Causes of an earthquake ==

{{main|plate tectonics}}

{{main|plate tectonics}}

Earthquakes are caused by tectonic movements in the Earth's crust. The main cause is when [[Plate tectonics|tectonic plates]] ride one over the other, causing [[orogeny]] (mountain building), and severe earthquakes.

Earthquakes are caused by tectonic movements in the Earth's crust. The main cause is that when [[Plate tectonics|tectonic plates]] collide, one rides over the other, causing [[orogeny]] (mountain building), earthquakes and [[volcano]]es.  

 

The boundaries between moving plates form the largest [[Fault (geology)|fault]] surfaces on Earth. When they stick, motion between the plates leads to increasing stress. This continues until the stress rises and breaks, suddenly allowing sliding over the locked portion of the fault. This releases the [[Potential energy|stored energy]] as [[shock wave]]<nowiki/>s. The [[San Andreas Fault|San Andreas fault]] in [[San Francisco]], and [[Great Rift Valley|Rift valley]] fault in [[Africa]] are faults like this.

2. Collapse Earthquakes : In areas of intense mining activity, often the roofs of underground mines collapse and minor tremors take place. These are called collapse earthquakes.

== Earthquake fault types ==

== Earthquake fault types ==

There are three main types of fault that may cause an earthquake: normal, reverse (thrust) and strike-slip. Normal faults occur mainly in areas where the crust is being extended. Reverse faults occur in areas where the crust is being shortened. Strike-slip faults are steep structures where the two sides of the fault slip horizontally past each other.

[[File:EastHanSeismograph.JPG|thumb|Replica of ancient [[seismometer]] with pendulum sensitive to ground tremors. In [[Luoyang]] in 133&nbsp;AD, it detected an earthquake 400 to 500&nbsp;km (250 to 310&nbsp;mi) away|270x270px]]There are three main types of [[Fault (geology)|geological fault]] that may cause an earthquake: normal, reverse (thrust) and strike-slip. Normal faults occur mainly in areas where the crust is being extended. Reverse faults occur in areas where the crust is being shortened. Strike-slip faults are steep structures where the two sides of the [[Fault (geology)|fault]] slip horizontally past each other.

== Earthquake clusters ==

== Earthquake clusters ==

Most earthquakes form part of a sequence, related to each other in terms of location and time.<ref name=WAAFEC>{{Cite web|url=http://earthquake.usgs.gov/eqcenter/step/explain.php|title=What are aftershocks, foreshocks, and earthquake clusters?}}</ref> Most earthquake clusters consist of small tremors which cause little to no damage, but there is a theory that earthquakes can recur in a regular pattern.<ref>{{cite web|url=http://earthquake.usgs.gov/research/parkfield/repeat.php|title=Repeating earthquakes|publisher=[[United States Geological Survey]]|date=January 29, 2009|accessdate=May 11, 2009}}</ref>

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?}}</ref> Most earthquake clusters consist of small tremors which 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|accessdate=May 11, 2009}}</ref>

A '''[[foreshock]]''' is an earthquake that occurs before a larger earthquake, the mainshock. A foreshock is in the same area of the main shock but always of a smaller magnitude.<ref name="Gates">{{cite book|last1=Gates|first1=A.|last2=Ritchie|first2=D.|title=Encyclopedia of Earthquakes and Volcanoes|url=http://books.google.co.uk/books?id=b1sXfJCiCHQC&pg=PA89|year=2006|publisher=Infobase Publishing|isbn=978-0-8160-6302-4|page=89}}</ref>

A '''[[foreshock]]''' is an earthquake that occurs before a larger earthquake, called the mainshock.

An '''[[aftershock]]''' is an earthquake that occurs after a previous earthquake, the mainshock. An aftershock is in the same region of the main shock but always of a smaller magnitude. Aftershocks are formed as the crust adjusts to the effects of the main shock.<ref name=WAAFEC/>

An '''[[aftershock]]''' is an earthquake that occurs after a previous earthquake, the mainshock. An [[aftershock]] is in the same region of the main shock but always of a smaller magnitude. Aftershocks are formed as the crust adjusts to the effects of the main shock.<ref name=WAAFEC/>

'''Earthquake swarms''' are sequences of earthquakes striking in a specific area within a short period of time. They are different from earthquakes followed by a series of aftershocks by the fact that no single earthquake in the sequence is obviously the main shock, therefore none have notable higher magnitudes than the other. 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=USGS|accessdate=2008-09-15}}</ref>

'''Earthquake swarms''' are sequences of earthquakes striking in a specific area within a short period of time. They are different from earthquakes followed by a series of aftershocks by the fact that no single earthquake in the sequence is obviously the main shock, therefore none have notably higher magnitudes than the other. 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=USGS|accessdate=2008-09-15}}</ref>

Sometimes a series of earthquakes occur in a sort of '''earthquake storm''', where the earthquakes strike a fault in clusters, each triggered by the shaking or stress redistribution of the previous earthquakes. Similar to aftershocks but on adjacent segments of fault, these storms occur over the course of years, and with some of the later earthquakes as damaging as the early ones. Such a pattern occurred in the North [[Anatolia]]n fault in [[Turkey]] in the 20th century.<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 | pages = 43–63 | url = http://water.stanford.edu/nur/EndBronzeage.pdf | doi = 10.1006/jasc.1999.0431 }}</ref><ref>{{cite web | url = http://www.bbc.co.uk/science/horizon/2003/earthquakestorms.shtml | title = Earthquake storms | work = Horizon (BBCtv series) | date = 9pm 1 April 2003 | accessdate = 2007-05-02 }}</ref>

Sometimes a series of earthquakes occur in a sort of '''earthquake storm''', where the earthquakes strike a fault in clusters, each triggered by the shaking or stress redistribution of the previous earthquakes. Similar to aftershocks but on adjacent segments of fault, these storms occur over the course of years, and with some of the later earthquakes as damaging as the early ones. Such a pattern occurred in the North [[Anatolia]]n fault in [[Turkey]] in the 20th century.<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 | pages = 43–63 | url = http://water.stanford.edu/nur/EndBronzeage.pdf | doi = 10.1006/jasc.1999.0431 }}</ref><ref>{{cite web | url = http://www.bbc.co.uk/science/horizon/2003/earthquakestorms.shtml | title = Earthquake storms | work = Horizon (BBCtv series) | date = 1 April 2003 | accessdate = 2007-05-02 }}</ref>

== Tsunami ==

== Tsunami ==

{{main|Tsunami}}

{{main|Tsunami}}

[[File:20110311Houshu.ogg|thumb|left|Animation of the 2011 Sendai [[tsunami]].]]

[[File:20110311Houshu.ogv|thumb|right|Animation of the 2011 Sendai [[tsunami]].]]

'''Tsunami''' or a [[chain]] of fast moving [[wave]]s in the [[ocean]] caused by powerful earthquakes is a very serious challenge for people's safety and for [[earthquake engineering]]. Those waves can inundate coastal areas, destroy [[house]]s and even swipe away whole [[town]]s.<ref>[http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc0001xgp.php USGS Poster of the Near the East Coast of Honshu, Japan Earthquake of 11 March 2011 - Magnitude 8.9]</ref>

'''[[Tsunami]]''' or a [[chain]] of fast moving [[wave]]s in the [[ocean]] caused by powerful earthquakes is a very serious challenge for people's safety and for [[earthquake engineering]]. Those waves can [[inundate]] coastal areas, destroy [[house]]s and even swipe away whole [[town]]s.<ref>[https://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc0001xgp.php USGS Poster of the Near the East Coast of Honshu, Japan Earthquake of 11 March 2011 - Magnitude 8.9]</ref> This is a danger for the whole mankind.

Unfortunately, tsunamis can not be prevented. However, there are warning systems<ref>[http://ptwc.weather.gov Pacific Tsunamy Warning Center]</ref> which may warn the [[population]] before the big waves reach the [[land]] to let them enough time to rush to safety.

Unfortunately, tsunamis can not be prevented. However, there are [[Tsunami warning system|warning systems]]<ref>[http://ptwc.weather.gov Pacific Tsunamy Warning Center]</ref> which may warn the [[population]] before the big waves reach the [[land]] to let them enough time to rush to safety.we aware of this tsunami

== Earthquake-proofing ==

== Earthquake-proofing ==

{{main|Earthquake engineering}}

{{main|Earthquake engineering}}

Earthquake-proof buildings are constructed to withstand the destructive force of an earthquake. This depends upon its type of construction, shape, [[mass]] distribution, and [[wikt:rigid|rigidity]]. Different combinations are used. Square, rectangular, and shell-shaped buildings can withstand earthquakes better than [[skyscraper]]s. To reduce stress, a building's ground floor can be supported by extremely rigid, hollow columns, while the rest of the building is supported by flexible columns inside the hollow columns. Another method is to use rollers or rubber pads to separate the base columns from the ground, allowing the columns to shake parallel to each other during an earthquake.

Earthquake-proof buildings are constructed to withstand the destructive force of an earthquake. This depends upon its type of construction, shape, [[mass]] distribution, and [[wikt:rigid|rigidity]]. Different combinations are used. Square, rectangular, and shell-shaped buildings can withstand earthquakes better than [[skyscraper]]s. To reduce stress, a building's ground floor can be supported by extremely rigid, hollow columns, while the rest of the building is supported by flexible columns inside the hollow columns. Another method is to use rollers or rubber pads to separate the base columns from the ground, allowing the columns to shake parallel to each other during an earthquake.

To help prevent a roof from collapsing, builders make the roof out of light-weight materials. Outdoor walls are made with stronger and more reinforced materials such as steel or [[reinforced concrete]]. During an earthquake flexible windows may help hold the windows together so they don’t break.

To help prevent a roof from collapsing, builders make the roof out of light-weight materials. Outdoor walls are made with stronger and more reinforced materials such as steel or [[reinforced concrete]]. During an earthquake flexible windows may help hold the windows together so they don’t break.

== Notes ==

== Sources ==

<references/>

<references/>

== Other websites ==

== Other websites ==

{{Commons category|Earthquake damage}}

{{Commons category|Earthquakes}}

* [http://www.pbs.org/newshour/science/earthquake/ PBS NewsHour - Predicting Earthquakes]

* [https://www.pbs.org/newshour/science/earthquake/ PBS NewsHour - Predicting Earthquakes]

* [http://neic.usgs.gov/neis/eqlists/10maps_world.html USGS – Largest earthquakes in the world since 1900]

* [http://neic.usgs.gov/neis/eqlists/10maps_world.html USGS – Largest earthquakes in the world since 1900]

* [http://www.armageddononline.org/earthquake.php The Destruction of Earthquakes] - a list of the worst earthquakes ever recorded

* [http://www.armageddononline.org/earthquake.php The Destruction of Earthquakes] - a list of the worst earthquakes ever recorded

* [http://earthquake.usgs.gov/eqcenter/recenteqsww/ Recent Quakes WorldWide]

* [https://earthquake.usgs.gov/eqcenter/recenteqsww/ Recent Quakes WorldWide]

[[Category:Earthquakes|*]]

[[Category:Earthquakes|*]]

[[Category:Plate tectonics]]

[[Category:Plate tectonics]]