Lect 25 Earthquakes 1

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Lect 25 Earthquakes 1

  1. 2. Causes of Earthquakes <ul><li>Types and Behavior of Seismic Waves </li></ul><ul><li>Body Waves </li></ul><ul><ul><li>Primary or Compressional </li></ul></ul><ul><ul><li>Secondary or Shear </li></ul></ul><ul><li>Surface Waves </li></ul><ul><ul><li>Raleigh (large vertical displacements) </li></ul></ul><ul><ul><li>Love (shear) </li></ul></ul>
  2. 3. Elastic Rebound Theory 3 m offset
  3. 4. Earthquake Focus and Hypocenter
  4. 5. Seismic Wave Types Body Waves Surface Waves
  5. 6. V p = k + 4/3µ  1/2 equations for velocities  density µ shear modulus (rigidity) k bulk modulus (rigidity) V s = µ  1/2 because shear modulus (rigidity) for fluid is zero, S waves cannot propagate through a fluid consequence of equations is that P waves are 1.7x faster than S can infer physical properties from P and S waves
  6. 7. Locating and Measuring Earthquakes <ul><li>Determining the Location of an Earthquake </li></ul><ul><li>Measuring the Size of an Earthquake </li></ul><ul><li>Location and Size of Earthquakes in the United States </li></ul>
  7. 8. Vertical Component Seismometer
  8. 9. Horizontal Component Seismomter
  9. 10. Distance - Time Relations
  10. 11. Earthquake Location by Range
  11. 12. Effects of Earthquakes <ul><li>Tsunamis </li></ul><ul><li>World Distribution of Earthquakes </li></ul><ul><li>First-Motion Studies of Earthquakes </li></ul>
  12. 13. Modified Mercalli Intensity Index (1931) 1886 Charleston, SC earthquake
  13. 14. Pancaked Building - 1985 Mexico City Earthquakes don’t kill people - buildings do!

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