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Earth Science Prentice Hall Upper Saddle River, NJ 1997 7:13 PM 10/9/2003
Earthquakes What an earthquake is made of and how it happens The Earth's crust is made of many tectonic plates that are floating on a layer of magma. The plates tend to crack and break. These cracks are known as faults. There are 4 major types of faults. These faults are normal faults, reverse faults, thrust faults, and lateral faults. Any movement of the tectonic plates along these faults will create an earthquake. Points of the earthquakes The point where the plates move or break is known as the focus point. It is generally beneath the surface and is the origin of the earthquake. On the surface is where the shaking takes place. This is known as the epicenter. Seismic energy waves are produced at the focus point and felt at the epicenter. Earthquakes under water Earthquakes that occur under the ocean floor send seismic waves to the surface. This energy creates giant ocean waves that move toward shore. These giant waves are known as tsunamis. Home |