Earthquake Presentation 08 09
- 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
- 6. *due to one or a combination of more than one of three kinds of forces : 1. tension 2. compression 3. shearing
- 8. Forces may cause rock to: 1 . * Fracture breaks in rock where no movement has occurred
- 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
- 17. Reverse Fault
- 18. Reverse Fault
- 19. Reverse Fault
- 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
- 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
- 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
- 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