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Understanding Earthquakes: Causes, Waves, & Effects

Learn about earthquakes caused by tectonic plate movements, deformation of rocks, and seismic waves. Discover how seismic waves travel and the types of waves produced during earthquakes.

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Understanding Earthquakes: Causes, Waves, & Effects

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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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