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EARTHQUAKES
Lesson 1 - Page 5

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These basic stresses caused by rotation and convection are just too much for the lithosphere. It relieves its stress by "cracking" or better known as faults. However, the movement along the faults cause energy to be released called seismic waves. When the waves reach the surface of the Earth it shakes, causing earthquakes.

Earthquakes are caused by the sudden movement and fracturing of rock masses along pre-existing faults. A fault is a broken surface within the Earth’s crust. The point on the fault at which the displacement begins is called the focus of the earthquake. The point on the surface of the earth directly above the focus is the epicenter. Faults can be caused by pull apart (extensional), compressional, or slip slide (transform) motion. 

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