3. Crust 6-7 km/sec Mantle 8-13 km/sec Outer Core 8-10 km/sec Inner Core 10-11 km/sec P-wave Velocities

7. K = bulk modulus = resistance of material to squeezing G = shear modulus = resistance of material to shearing D = density

9. Seismological Results Values of K, G and D at a given point in the Earth’s interior. Search for materials with appropriate values of K, G and D Estimates of composition of different parts of the Earth’s interior

10. G = 0 for liquids Outer Core of Earth is liquid

11. From: Understanding Earth by Press, Siever, Grotzinger and Jordan

14. From: www.yorku.ca/eye/refract.htm

15. speed of light in a vacuum = 300,000,000 m/s speed of light in glass = 200,000,000 m/s From: www.what-is-the-speed-of-light.com

16. Slow Fast

19. M=7.8, ∆=62° Magnitude 7.8 TARAPACA, CHILE, June 13, 2005 22:45 UTC Boston, Massachusetts - First Wave Arrives 22:55 (10 minutes)

20.  Distanced measured in degrees from epicenter. Travel-time versus Distance

21. M=7.6, ∆=97° Boston, Massachusetts - First Wave Arrives 4:04 (13 minutes) Magnitude 7.6 PAKISTAN, October 08, 2005 at 03:51 UTC

22. M=6.7, ∆=25° Magnitude 6.8 CAYMAN ISLANDS, December 14, 2004 at 23:20 UTC Boston, Massachusetts - First Wave Arrives 23:26 (6 minutes)

24. Distance Travel Time

25. 6371 km 1 2 3 Path Distance (km) Time (sec) Velocity 1 2,758 360 7.7 km/sec 2 6,563 600 10.9 km/sec 3 9,543 780 12.2 km/sec

26. Crust 6-7 km/sec Mantle 8-13 km/sec Outer Core 8-10 km/sec Inner Core 10-11 km/sec P-wave Velocities

27. Crust 6-7 km/sec Mantle 8-13 km/sec Outer Core 8-10 km/sec Inner Core 10-11 km/sec P-wave Velocities Air: 0.3 Water: 1.4 Concrete: 3.6 Granite: 5.5-6.0 Iron: 5.8 Aluminum: 6.6

28.   T Distanced measured in degrees from epicenter. Travel-time versus Distance Curves

29.  Distanced measured in degrees from epicenter. Travel-time versus Distance Curves

30. P-wave reflected from Core-Mantle Boundary PcP

31. Fast Slow

33. “Moho” Andrija Mohorovicic Zagreb Seismological Observatory 1909

35. “Moho” Andrija Mohorovicic Zagreb Seismological Observatory 1909

36. Slow Fast

38. Slow Fast

40. Inner Core discovered by Inge Lehmann in 1936 Copenhagen Seismological Observatory

41. Inner Core discovered by Inge Lehmann in 1936 Copenhagen Seismological Observatory

43. Low Velocity Zone in Upper Mantle

44. Low Velocity Zone = Asthenosphere of Plate Tectonics

45. From Understanding Earth by Press, Siever, Grotzinger and Jordan (2004).

46. Mechanism of Plate Tectonics

47. Crust 6-7 km/sec Mantle 8-13 km/sec Outer Core 8-10 km/sec Inner Core 10-11 km/sec P-wave Velocities

48. Variations in seismic velocity (+/- a few percent) are depicted by warm (low velocity) or cool (high velocity) colors. Seismic Tomography