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Earthquakes

Earthquakes. October 31, 2013. What exactly is an earthquake?. Any rapid deformation of the earth caused by motion of tectonic plates Studied by seismologists Occur whenever plates move in different directions and at different speeds plates can push toward, pull away, or slide past

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Earthquakes

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  1. Earthquakes October 31, 2013

  2. What exactly is an earthquake? • Any rapid deformation of the earth caused by motion of tectonic plates • Studied by seismologists • Occur whenever plates move in different directions and at different speeds • plates can push toward, pull away, or slide past Produce faults which are breaks in the Earth’s crust

  3. What actually causes earthquakes? • Pressure created by tectonic plates can cause rocks to deform • 2 ways • Plastic deformation – changes shape of rock • Ex. Molded clay Elastic deformation – bending of rock that DOES lead to earthquakes • Ex. Branch breaking after bending

  4. How does elastic deformation produce earthquakes? • Elastic rebound theory – the sudden return to unstressed point • Releases huge amount of energy as seismic waves • Can produce damage depending on the amount of energy released and type of material it travels through

  5. How do seismic waves travel? • Seismic waves travel through the interior of the earth and are called body waves • 2 types • P waves (pressure or primary) • Can travel through solids, liquids, and gases • Fastest of seismic waves • Causes particles of rock to move in a back-and-forth motion

  6. What’s the second type? • S wave (shear or secondary) • Can not travel through liquids (proof that the earth is not completely solid) • Move in side-to-side motion • Move slower than P waves

  7. Is that all the waves? • No • Surface waves – move along the earth’s surface in the upper few kilometers of the earths crust • Move across surface like a ocean wave • Travel much slower and are much more destructive

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