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Earthquakes

Earthquakes. What is an earthquake? . A vibration of the Earth produced by a rapid release of energy Often occur along faults – breaks in the Earths crust and mantle (plate boundaries). 2 important points. 1. Focus – Point within the Earth where the earthquake starts

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Earthquakes

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  1. Earthquakes

  2. What is an earthquake? • A vibration of the Earth produced by a rapid release of energy • Often occur along faults – breaks in the Earths crust and mantle (plate boundaries)

  3. 2 important points • 1. Focus – Point within the Earth where the earthquake starts • Energy moves in all directions from this point • 2. Epicenter – Point on the Earth’s surface directly above the focus • Most intense movement during the earthquake

  4. Causes of Earthquakes • The Elastic Rebound Hypothesis • Stress builds along an existing fault • Deformation of crustal rock – bent features of the rocks caused by increasing stress – elastic energy • Slippage (earthquake) – energy is stored in the rock overcomes frictional forces keeping crust in place • Energy released – rock returns to original shape

  5. Earthquake Waves • Measured by a seismograph(instrument) • Seismographs produce seismograms – the written record of the movement

  6. 3 Types of Earthquake Waves • Surface Waves – earthquake waves that travel along the Earth’s outer layer • Up and down, side to side, twisting motion • Most destructive of the waves • Slowest wave

  7. 3 Types of Earthquake Waves P waves: (Body waves) • Compression waves • Alternately expand and compress material they pass through • Travel the fastest of all three waves • Travels parallel to its movement

  8. 3 Types of Earthquake Waves S Waves (Body waves) • Transverse wave • Travel slower than P waves • Travels at a right angle to the direction of its movement • Will not travel through liquids and gases

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