Earthquakes are caused by sudden movements within Earth's crust that cause rocks to bend, break or fracture. Most earthquakes occur along the Ring of Fire, a belt circling the Pacific Ocean where 88% of all quakes take place, and also along other belts where tectonic plates meet. Forces like tension, compression and shearing cause three types of rock fractures - normal faults where the rock moves apart, reverse faults where it moves together, and strike-slip faults where it slides horizontally past another part of the crust.

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

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

17. Reverse Fault

18. Reverse Fault

19. Reverse Fault

21. Reverse Fault Structures

22. Strike-slip (Transform) Fault

23. Strike-slip (Transform) Fault

24. Strike-Slip Fault

26. Strike Slip 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

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

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

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