Download Earthquake Notes

Earthquakes
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Earthquakes occur when vast plates, or rocks, within the Earth suddenly break or shift under stress,
sending shock waves rippling.
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Sudden movement along the fault causes the ground to shake.
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Most earthquakes occur along fractures in the Earth's crust called faults.
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Intraplate quakes occur far from plate edges and happen when stress builds up and the Earth's
crust is stretched or squeezed together until it rips.
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There are several different types of faults. Each can be a few inches or many hundreds of miles
long. They can be horizontal, vertical, or at an angle.
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Earthquake waves are measured on sensitive instruments called seismographs.
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The Richter scale assigns quakes a number based on the power of its seismic waves.
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Thousands of quakes occur every day around the globe, most of them too weak to be felt.
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Every year about 10,000 people, on average, die as a result of earthquakes