earthquakes
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Earthquakes are the shaking of the earth. The study of earthquakes is a seismology. Earthquakes are complex, and they present many questions for seismolgist, which is a person who studies earthquakes. Most earthquakes take place near the edges of the tectonic plates. Tectonic plates are gaint pieces of earth's thin, outermost layer. A fault is a break in the Eath's crust along which blocks of the crust slide relative to one another. Earthquakes occur along faults becuase of this sliding. When a earthquake happens, vibration called seismic waves are produced. When an earthquake happens, machines called Seismographs measure the times at which seismic waves arrive at different distances from an earthquake.
Holt Science and Technology Earth Science pg. 224- 229 http://www.uh.edu/~jbutler/physical/chapter18.html
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