Changes

[[File:lighterstill.jpg]][[File:San-Francisco-earthquake-of-1906.jpg|right|frame]]

[[File:lighterstill.jpg]][[File:San-Francisco-earthquake-of-1906.jpg|right|frame]]

*[http://en.wikipedia.org/wiki/14th_century 14th Century]

*[https://en.wikipedia.org/wiki/14th_century 14th Century]

==Definitions==

==Definitions==

*1: a shaking or trembling of the [[earth]] that is volcanic or [[tectonic]] in [[origin]]

*1: a shaking or trembling of the [[earth]] that is volcanic or [[tectonic]] in [[origin]]

*2: upheaval  

*2: upheaval  

==Description==

==Description==

An '''earthquake''' (also known as a quake, tremor or temblor) is the result of a sudden release of [[energy]] in the [[Earth]]'s [http://en.wikipedia.org/wiki/Crust_(geology) crust] that creates [http://en.wikipedia.org/wiki/Seismic_wave seismic waves]. The seismicity or seismic activity of an area refers to the [[frequency]], [[type]] and size of earthquakes experienced over a period of [[time]]. Earthquakes are [[measured]] with a [http://en.wikipedia.org/wiki/Seismometer seismometer]; a device which also records is known as a seismograph. The [http://en.wikipedia.org/wiki/Moment_magnitude_scale moment magnitude] (or the related and mostly obsolete [http://en.wikipedia.org/wiki/Richter_magnitude_scale Richter] magnitude) of an earthquake is conventionally reported, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. [[Intensity]] of shaking is [[measured]] on the modified [http://en.wikipedia.org/wiki/Mercalli_intensity_scale Mercalli scale]. The depth of the earthquake also matters: the more shallow the earthquake, the more damage to [[structures]] (all else being [[equal]]).

An '''earthquake''' (also known as a quake, tremor or temblor) is the result of a sudden release of [[energy]] in the [[Earth]]'s [https://en.wikipedia.org/wiki/Crust_(geology) crust] that creates [https://en.wikipedia.org/wiki/Seismic_wave seismic waves]. The seismicity or seismic activity of an area refers to the [[frequency]], [[type]] and size of earthquakes experienced over a period of [[time]]. Earthquakes are [[measured]] with a [https://en.wikipedia.org/wiki/Seismometer seismometer]; a device which also records is known as a seismograph. The [https://en.wikipedia.org/wiki/Moment_magnitude_scale moment magnitude] (or the related and mostly obsolete [https://en.wikipedia.org/wiki/Richter_magnitude_scale Richter] magnitude) of an earthquake is conventionally reported, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. [[Intensity]] of shaking is [[measured]] on the modified [https://en.wikipedia.org/wiki/Mercalli_intensity_scale Mercalli scale]. The depth of the earthquake also matters: the more shallow the earthquake, the more damage to [[structures]] (all else being [[equal]]).

At the [[Earth]]'s surface, earthquakes [[manifest]] themselves by shaking and sometimes displacing the ground. When a large earthquake [http://en.wikipedia.org/wiki/Epicenter epicenter] is located offshore, the seabed sometimes suffers sufficient displacement to cause a [http://en.wikipedia.org/wiki/Tsunami tsunami]. The shaking in earthquakes can also trigger landslides and occasionally volcanic activity.

At the [[Earth]]'s surface, earthquakes [[manifest]] themselves by shaking and sometimes displacing the ground. When a large earthquake [https://en.wikipedia.org/wiki/Epicenter epicenter] is located offshore, the seabed sometimes suffers sufficient displacement to cause a [https://en.wikipedia.org/wiki/Tsunami tsunami]. The shaking in earthquakes can also trigger landslides and occasionally volcanic activity.

In its most generic sense, the word earthquake is used to describe any seismic event—whether a [[natural]] [[phenomenon]] or an event caused by [[humans]]—that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults, but also by volcanic activity, landslides, mine blasts, and [http://en.wikipedia.org/wiki/Underground_nuclear_testing nuclear tests]. An earthquake's point of initial rupture is called its [[focus]] or [http://en.wikipedia.org/wiki/Hypocenter hypocenter]. The term [http://en.wikipedia.org/wiki/Epicenter epicenter] refers to the point at ground level directly above the hypocenter.[http://en.wikipedia.org/wiki/Earthquake]

In its most generic sense, the word earthquake is used to describe any seismic event—whether a [[natural]] [[phenomenon]] or an event caused by [[humans]]—that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults, but also by volcanic activity, landslides, mine blasts, and [https://en.wikipedia.org/wiki/Underground_nuclear_testing nuclear tests]. An earthquake's point of initial rupture is called its [[focus]] or [https://en.wikipedia.org/wiki/Hypocenter hypocenter]. The term [https://en.wikipedia.org/wiki/Epicenter epicenter] refers to the point at ground level directly above the hypocenter.[https://en.wikipedia.org/wiki/Earthquake]

[[Category: Earth Science]]

[[Category: Earth Science]]