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Crust 6-7 km/sec

P-wave Velocities. Crust 6-7 km/sec. Mantle 8-13 km/sec. Outer Core 8-10 km/sec. Inner Core 10-11 km/sec. K = bulk modulus = resistance of material to squeezing. D = density. G = shear modulus = resistance of material to shearing. Seismological Results

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Crust 6-7 km/sec

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

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

  3. 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

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

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

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

  7. 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

  8. Slow Fast Slow Fast

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

  10. Travel-time versus Distance D Distanced measured in degrees from epicenter.

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

  12. 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)

  13. Travel Time Distance

  14. 1 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 2 3 6371 km

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

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

  17. Travel-time versus Distance Curves T D Distanced measured in degrees from epicenter. D

  18. Travel-time versus Distance Curves D Distanced measured in degrees from epicenter.

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

  20. Slow Fast

  21. “Moho” Andrija Mohorovicic Zagreb Seismological Observatory 1909

  22. “Moho” Andrija Mohorovicic Zagreb Seismological Observatory 1909

  23. Fast Slow

  24. Fast Slow

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

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

  27. Low Velocity Zone in Upper Mantle

  28. Low Velocity Zone in Upper Mantle Low Velocity Zone = Asthenosphere of Plate Tectonics

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

  30. Mechanism of Plate Tectonics

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

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

  33. Seismic Tomography

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