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Earthquake Presentation 08 09

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Transcript

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