What is an earthquake and what causes them to happen?

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Hello and welcome to CoreFacts, where we're always short on time and big on science. I'm Steve Sobieszczyk. Today we're looking at some introductory geology with:

What is an earthquake and what causes them to happen?

One of the most frightening and destructive phenomena of nature is a severe earthquake and its terrible aftereffects. An earthquake is caused by a sudden slip on a fault, often abruptly releasing strain that has accumulated over a long period. For hundreds of millions of years, the forces of plate tectonics have shaped the Earth as the huge plates that form the Earth's surface slowly move over, under, and past each other. The tectonic plates are always moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel. If the earthquake occurs in a populated area, it may cause many deaths and injuries and extensive property damage.

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