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Earth Science Chapter 8
∑ Seismology is the study of earthquakes.
∑ Earthquakes occur mostly at the edges of tectonic plates, giant masses of solid rock that cover the earth.
∑ Faults, which are breaks in the Earthís crust, are especially present at tectonic plate boundaries.
∑ Rocks stretch and squeeze like a spring during an earthquake, which causes seismic waves.
∑ Seismic waves inside the Earth are body waves, and seismic waves on the Earthís surface are surface waves.† Surface waves are more destructive.
∑ Seismographs help to locate earthquakes, determine when they occurred, and measure their strength.
∑ The Richter scale is used to measure earthquake strength.† A one point increase on the scale indicates a 31.7 times increase in energy release.
∑ On the Richter scale, a magnitude of 2.0 is small and canít be felt by humans.† A magnitude of 4.0 can be felt by most in the area.† A magnitude of 6.0 causes widespread damage, and a magnitude of 7.0 causes the greatest damage.
∑ Buildings are often constructed to resist earthquakes.† Flexible pipes prevent water and gas lines from breaking.† Base isolators use steel and rubber to absorb shock.
∑ In the event of an earthquake, the best thing to do is lie or crouch under cover in the center of the room.† If youíre in a car outside, remain in the car.
∑ Seismographs left on the moon have detected moonquakes.
∑ Sunquakes are caused by solar flares, powerful magnetic disturbances in the sun.