2. EARTHQUAKES Chapter 15

3. Recent quakes (last 7 days) http://earthquake.usgs.gov/earthq uakes/recenteqsww/

5. LARGEST QUAKES SINCE 1900 Chile19609.5 Alaska19649.2 Alaska19579.1 Sumatra 20049.1 Japan20119.0 Chile 20108.8

6. MAJOR RECENT QUAKES China 7.9 5/12/08 87,000 Sumatra 7.0 12/26/04 230,000 Haiti 7.0 1/12/10 316,000 Chile 8.82/27/10 810 Japan 9.03/11/11 28,000 + Philippines 6.7 2/6/12113

7. Michigan earthquakes Year Date Mag. City 1877 Aug 17 3.2 Greenfield 1938 Mar 13 3.8 Gibralter 1938 Mar 14 ? Gibralter 1947 Aug 10 4.7 Coldwater 1977 Oct 26 2.7 L Superior 1980 Apr 29 0.5 L Superior 1982 Nov 26 2.5 Scotts 1994 Sep 02 3.4 Central Lansing 2001 Oct 23 2.9 Prairie L

8. What is an Earthquake? Vibration of earth from rapid release of energy Movement at focus above focus is the epicenter

9. Elastic rebound theory

11. Aftershocks “Readjustment” of the plate in it’s new position Due to Elastic rebound theory Bigger earthquakes= bigger aftershocks

12. Normal fault tensional stress footwall Hanging wall

13. Reverse (thrust) fault compressional stress footwall Hanging wall

15. Strike slip shearing stress

16. San Andreas Fault

20. EARTHQUAKE WAVES

21. Measured by a seismograph

23. P waves Primary travel fastest travels through liquids and solids compressional wave –push/pull

25. S waves Secondary travels only through solids shearing wave –back and forth motion

27. Surface waves Travel on surface slow similar to water waves Usually cause most damage

30. GPS seismometer

34. Label layers

35. Seismic waves S waves do NOT travel through liquids

36. Mantle= P + S waves= solid Outer core= P waves only= liquid Inner core-= solid

37. Locating an epicenter use lag time between P and S waves to calculate the distance the epicenter was from the seismograph Doesn’t tell direction

39. INTENSITY OF QUAKE Depends on –energy released (magnitude) –distance from epicenter –rock type (soft=worse) –depth

40. SCALES Mercalli –Created in 1902 (before seismographs) –measures damage –I- XII –Depends on population, building type

42. Coldwater, MI 1947

43. RICHTER SCALE Developed by Charles Richter (1935) Measures ground shaking- each step is 10x higher wave amplitude Each step is 32x more energy- logarithmic 4.5 compared to 6.5 energy=

45. Richter Scale (M L ) Under 2 not felt by humans Designed for California shallow quakes Not accurate for large quakes

46. Moment- Magnitude Scale (M w ) More accurate than Richter, especially for large quakes Mw= Area of fault’s rupture X slippage X rock resistance

47. Where do quakes happen? At plate boundaries (most of the time)

48. Quakes outline plate boundaries

49. Depth of quakes

50. PLATE BOUNDARIES Divergent –small –shallow –normal faults

52. PLATE BOUNDARIES CONVERGENT –Most major quakes –reverse faults –Shallow through deep

53. PLATE BOUNDARIES INTRAPLATE –asthenosphere causes vertical movement? –Ancient faults?

58. Earthquake hazards Structural damage –Most prevalent Tsunamis Fires (electrical lines + gas lines) landslides

67. Peru 2007

68. Pakistan 2005

76. Chile Feb. 27, 2010 8.8 Mw Depth 35 km 486 deaths Reverse fault Moved Santiago 11 inches to the west

79. Alaskan school, Good Friday 1964

80. Olympia WA, 1949