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An '''earthquake''' is the shaking caused when [[plate tectonics|tectonic]] activity in an area causes the release of stored [[energy]] from the rock. Most commonly occurring on tectonic plate boundaries, earthquakes also occur along [[fault]]s where previous movement has occurred.

An '''earthquake''' is when the [[Earth]] shakes, caused by [[plate tectonics|tectonic]] activity in an area after the release of stored [[energy]] from the [[rock]]. Earthquakes most commonly occur on tectonic plate boundaries, and also occur along [[fault|faults]] where previous movement has occurred. There are 500,000 detectable earthquakes in the world each year.  

Earthquakes are a significant natural [[hazard]] to populations living in areas prone to earthquakes and responses to the hazard vary with economic development. The most powerful and destructive earthquakes occur at tectonic plate boundaries like the [[San Andreas Fault]].

Earthquakes are a significant natural [[hazard]] to populations living in areas prone to them, and emergency responses to the hazard vary with economic development. The most powerful and destructive earthquakes occur at tectonic plate boundaries like the [[San Andreas Fault]].

The severity of earthquakes is measured using the [[Richter scale]].

The severity of earthquakes is measured using the [[Richter scale]].

* [[seismic]]

* [[seismic]]

* [[Loma Prieta Earthquake]]

* [[Loma Prieta Earthquake]]

==External links==

==External links==

*[http://www.drgeorgepc.com/EarthquakesChina.html Historical Earthquakes in China]

*[http://www.drgeorgepc.com/EarthquakesChina.html Historical Earthquakes in China]

[[Category:Seismology]]

[[Category:Seismology]]

[[Category:Natural Disasters]]

[[Category:Natural Disasters]]