Earthquake Presentation 08 09

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Earthquake Presentation 08 09

  1. 1. Earthquakes are the vibrations caused by sudden movements of Earth’s rocks. Forces within the crust cause rocks to bend or break .
  2. 2. Where do most Earthquakes occur?
  3. 3. Most Earthquakes occur: <ul><li>*along the “Ring of Fire” , a belt which circles the Pacific Ocean </li></ul><ul><li>*88% of all earthquakes occur here </li></ul>
  4. 4. Earthquake Belts <ul><li>along the belts which run through </li></ul><ul><ul><li>central Asia </li></ul></ul><ul><ul><li>mid-ocean ridges </li></ul></ul><ul><ul><li>Mediterranean Sea </li></ul></ul><ul><ul><li>Caribbean Sea </li></ul></ul>Each black dot represents one earthquake over a 10 year period
  5. 5. Earthquake Belts
  6. 6. <ul><li>*due to one or a combination of more than one of three kinds of forces : </li></ul><ul><li>1. tension 2. compression 3. shearing </li></ul>
  7. 7. Elastic Rebound
  8. 8. Forces may cause rock to: <ul><li>1 . * Fracture </li></ul><ul><ul><li>breaks in rock where no movement has occurred </li></ul></ul>
  9. 10. Forces may cause rock to: <ul><li>2 . * Fault </li></ul><ul><ul><li>fractures in rock where movement has occurred </li></ul></ul><ul><ul><li>may occur in any direction along the surface of the break ( fault plane ) </li></ul></ul>
  10. 11. *Fault Types <ul><ul><li>may be one of three types : </li></ul></ul><ul><ul><li>1. normal </li></ul></ul><ul><ul><li>2. reverse </li></ul></ul><ul><ul><li>3. strike-slip (transform) </li></ul></ul>
  11. 12. Normal Fault
  12. 13. Normal Fault
  13. 14. Normal Fault
  14. 15. Normal Fault Structures
  15. 17. Reverse Fault
  16. 18. Reverse Fault
  17. 19. Reverse Fault
  18. 21. Reverse Fault Structures
  19. 22. Strike-slip (Transform) Fault
  20. 23. Strike-slip (Transform) Fault
  21. 24. Strike-Slip Fault
  22. 26. Strike Slip Fault
  23. 28. Forces may cause rock to: <ul><li>3 . * Fold </li></ul><ul><ul><li>due to compression </li></ul></ul><ul><ul><li>may form one single bend ( monocline ) </li></ul></ul><ul><ul><li>or may form alternating ridges ( anticlines ) </li></ul></ul><ul><ul><li>and troughs ( synclines ) </li></ul></ul>
  24. 29. monocline
  25. 30. anticlines
  26. 31. synclines
  27. 32. Folded Rocks anticline syncline Where are the oldest rocks exposed at the surface?
  28. 33. Folded Rocks monocline rock has a gently dipping bend in the horizontal rock layer.
  29. 34. Seismic Waves <ul><li>originate from the * focus , the actual point on the fault where movement occurs </li></ul><ul><li>affect the point on the earth surface directly above the focus, called the * epicenter </li></ul>
  30. 35. Seismic Waves <ul><li>may be a * body wave : </li></ul><ul><li>1. * P- wave (primary) - rocks particles back and forth, fastest wave, first to arrive </li></ul><ul><li>2. * S - wave (secondary) - rocks move forward but vibrate at right angles to the direction of movement, slower than p - wave, arrives later </li></ul>
  31. 36. Seismic Waves <ul><li>may be a * surface wave : </li></ul><ul><li>3. * L- wave (longitudinal) - vibrates the earth’s crust like an ocean wave </li></ul><ul><li>is the most destructive </li></ul><ul><li>travels very slow compared to P & S – waves </li></ul><ul><li>last to reach the seismic station </li></ul>
  32. 37. Seismic Waves
  33. 38. Earthquake Destruction <ul><li>Intensity </li></ul><ul><li>is a measure of the physical damage or geologic change </li></ul><ul><li>measured by the </li></ul><ul><li>Mercalli Scale </li></ul><ul><li>Magnitude </li></ul><ul><li>is a measure of the strength of an earthquake recorded by seismographs </li></ul><ul><li>measured by the </li></ul><ul><li>Richter Scale </li></ul>
  34. 40. How Seismographs Work
  35. 41. Seismograph
  36. 42. Richter Scale For every increase in 1 on the Richter Scale…. there is an increase of 32 times the energy released!
  37. 43. Seismogram
  38. 44. P and S Wave Travel Time Curves Use the difference in P and S wave arrival times to calculate the distance from the epicenter.
  39. 45. Locating Earthquakes Station 1 Station 1
  40. 46. Locating Earthquakes Station 2
  41. 47. Locating Earthquakes Station 3
  42. 49. Locating Earthquakes - Depth
  43. 50. Seismic Waves in the Earth
  44. 51. Seismic Waves in the Earth
  45. 52. Earth’s Interior <ul><li>P & S waves slow when they hit the upper mantle (asthenosphere) </li></ul><ul><li>speed up again when they hit the solid lower mantle </li></ul><ul><li>P waves are slowed and deflected when they hit the liquid outer core </li></ul>
  46. 53. Earth’s Interior <ul><li>S waves do not travel through the liquid outer core </li></ul><ul><li>Shadow Zone results between 105 o and 140 o from an earthquake’s focus </li></ul>
  47. 54. Earth’s Interior
  48. 55. Earth’s Interior Why is the inner core a solid?
  49. 56. Earth’s Interior <ul><li>Crust: 3 – 60 miles thick, hard, brittle, continents are thicker than ocean </li></ul><ul><li>Mantle: thickest layer, denser than crust, upper mantle is plastic-like (flows under pressure) </li></ul><ul><ul><li>Separated from the crust by the Moho or Mohorovicic Discontinuity </li></ul></ul><ul><ul><li>Made of silicon, oxygen, magnesium, iron </li></ul></ul>
  50. 57. Earth’s Interior <ul><li>Core: innermost layer, made of iron and nickel </li></ul><ul><ul><li>Inner core is solid </li></ul></ul><ul><ul><li>Outer core is liquid </li></ul></ul>
  51. 59. Earthquake Damage
  52. 60. Earthquake Damage
  53. 61. Earthquake Damage
  54. 62. Earthquake Damage
  55. 63. Earthquake Damage
  56. 64. Earthquake Damage
  57. 65. Earthquake Damage
  58. 66. Earthquake Damage
  59. 67. Earthquake Damage
  60. 68. Earthquake Damage
  61. 69. Earthquake Damage
  62. 70. Earthquake Safety <ul><li>Outdoors – move to an open area </li></ul><ul><ul><li>Stay away from chimneys, buildings, trees </li></ul></ul><ul><ul><li>Stay away from beaches </li></ul></ul><ul><li>Indoors </li></ul><ul><ul><li>move away from windows, large objects </li></ul></ul><ul><ul><li>Seek shelter under table, desk, doorway, basement stairs </li></ul></ul><ul><ul><li>Turn off electricity, water, gas if possible </li></ul></ul>
  63. 71. Tsunamis <ul><li>Probably Caused by Submarine Landslides </li></ul><ul><li>Travel about 400 m.p.h. </li></ul><ul><li>Pass Unnoticed at Sea, Cause Damage on Shore </li></ul>
  64. 72. Tsunamis <ul><li>Whether or Not Damage Occurs Depends on: </li></ul><ul><ul><li>Direction of Travel </li></ul></ul><ul><ul><li>Harbor Shape </li></ul></ul><ul><ul><li>Bottom topography </li></ul></ul><ul><ul><li>Tide & Weather </li></ul></ul>
  65. 73. Tsunamis
  66. 74. Satellite images from NASA show the destruction caused by a tsunami to the Indonesian province of Aceh. The left photo shows the town of Lhoknga before the tsunami hit on Dec. 24, 2004.
  67. 75. Tsunamis
  68. 76. Tsunamis
  69. 77. Tsunamis

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