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Earthquake
E
Earthquake
The sudden movement of a plate along a fault and the ground shaking that is caused by it.
An earthquake is a tear in
the rock, often called a rupture. Earthquakes can occur as deep as 750km below the surface. Most, however, are more shallow, being less than 70km deep.
There are 500,000 detectable earthquakes in the world each year. Of those, 100,000 can be felt, and about 100 cause damage. Ten per cent of all the world’s earthquakes occur in Japan.
The largest recorded earthquake in the United States was one of magnitude 9.2 that struck Prince William Sound, Alaska, on March 28, 1964. The largest recorded earthquake in the world was one
of magnitude 9.5 in Chile on May 22, 1960. The earliest reported earthquake in California was felt in 1769 by the expedition of Gaspar de Portola while the group was camping near Los Angeles.
The world’s most destructive earthquake in historic times occurred in central China in 1557. It happened in a region of soft
 Earthquake – Sometimes a fault can be seen at the surface, but more often it is a blind fault that never reaches the surface, and cracks are movements of the soil rather than the actual fault.
 Earthquake – The focus of an earthquake is usually where two crustal
rock. The houses and caves where people lived simply crumbled away during the earthquake and some 830,000 people died. In 1976 another deadly earthquake struck in Tangshan, China, and more than 250,000 people were killed.
Most earthquakes occur where great slabs of the Earth’s surface, called plates, move past one another. The majority of earthquakes occur where the Pacific Ocean plate pushes under the surrounding continents (part
of which includes California). Earthquakes are often accompanied
plates are moving relative to one another. This diagram shows an earthquake on the Benioff Zone, the region separating a continental from an oceanic plate.
Waves sent out from an earthquake
Shallow
100km Medium 200km
300km Deep 400km
0km
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