1. Earthquakes I used to sleep nude - until the earthquake. --Alyssa Milano

2. Where?

3. http://www.iris.edu/dms/seismon.htm

4. Where?

5. --Mainly at plate boundaries –Convergent and transform, usually –Sometimes in the middle of a plate

6. How?

7. Pressure builds up Rocks break when their shear strength is overcome Rock layer snap back with elastic rebound

8. How? Rocks move at a fault

9. How? Rocks move at a fault This motion makes earthquake waves

10. The epicenter is over the focus

11. Earthquake waves 3 types of waves: (see diagram, p G-128)

12. Earthquake waves 3 types of waves: primary (P) secondary (S) and surface (L)

13. Earthquake waves 3 types of waves: primary (P) secondary (S) and surface (L) L waves cause most of the damage. S and P waves tell us about the interior of the Earth.

14. Secondary waves Direction Called Barrier Velocity

15. Secondary waves Direction Called Barrier Velocity Side to side motion

16. Secondary waves Direction Called Barrier Velocity Side to side motion Shear waves

17. Secondary waves Direction Called Barrier Velocity Side to side motion Shear Stops at solid/liquid barrier

18. Secondary waves Direction Called Barrier Velocity Side to side motion Shear Stops at solid/liquid barrier Slower

19. Secondary waves Direction Called Barrier Velocity Side to side motion Shear Stops at solid/liquid barrier Slower

20. Primary waves Direction Called Barrier Velocity

21. Primary waves Direction Called Barrier Velocity Parallel to direction of travel

22. Primary waves Direction Called Barrier Velocity Parallel to direction of travel Pressure waves

23. Primary waves Direction Called Barrier Velocity Parallel to direction of travel Pressure waves Passes solid/liquid barrier

24. Primary waves Direction Called Barrier Velocity Parallel to direction of travel Pressure waves Passes solid/liquid barrier Phaster than S waves

25. Primary waves Direction Called Barrier Velocity Parallel to direction of travel Pressure waves Passes solid/liquid barrier Phaster than S waves

26. Seismographs http://www.wwnorton.com/college/geo/egeo/ flash/8_3.swf

27. Seismographs The pen is steady, paper is pulled under it. If the paper shakes, the line swings P waves reach the seismograph first The time lag before the S waves reach it tell you how far away the earthquake was

28. EARTHQUAKE!

29. P waves lead S waves by 2:30 in Denver

30. Epicenter is 2000 km from Denver

31. P waves lead S waves by 1:05 in Seattle

32. Epicenter is 800 km from Seattle

33. P waves lead S waves by 1:15 in LA

34. Epicenter is 900 km from LA

35. Epicenter is in SE Oregon!

36. Seismic evidence explains the different layers of the Earth.

37. S waves bend, but don’t penetrate the outer core

38. The outer core must be liquid!

39. S waves bend, but don’t penetrate the outer core The amount of bending indicates density

40. P waves penetrate the outer core

41. They bend as they cross layers

42. How big was this earthquake? Two observations geoscientists make about earthquakes. Magnitude and intensity

43. Magnitude Measured on the Richter scale Indicates energy released Log scale: --A magnitude 4 quake has 10 times the energy of magnitude 3.

44. Intensity Measured on the Mercalli scale Indicates what is felt From I to XII --Intensity III can barely be felt, --Intensity VIII knocks down buildings

45. Earthquake Risk Small earthquakes are more common than large ones http://www.iris.edu/dms/seismon.htm Plate boundaries are at greatest risk.

46. Earthquake Hazards 1) 2) 3) 4) 5) 6) 7)

47. Earthquake Hazards 1)Buildings fall down 2)Fires start 3)Landslides occur 4)Tsunami are triggered 5)Pipelines break 6)Power lines fall/break 7)Roads and bridges are damaged