Download
seismicity n.
Skip this Video
Loading SlideShow in 5 Seconds..
Seismicity PowerPoint Presentation

Seismicity

223 Vues Download Presentation
Télécharger la présentation

Seismicity

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Seismicity

  2. Seismic Image of Venezuela Basin

  3. Seismic waves

  4. Seismic wave travel in a homogeneous Earth

  5. Seismic wave travel in which density increases monotonously

  6. Seismic wave travel in a layered Earth

  7. The P-wave shadow zone

  8. The S-wave shadow zone

  9. P and S-wave velocities

  10. The Earth Interior

  11. The Earth Interior

  12. The distribution of land

  13. Hypsographic Curve • Extreme elevations are rare • Two common elevations • Ocean basins (abyssal plains) • Continental interiors Why??

  14. The weight of an Object is determined by its mass and the force of gravity F = the force of gravity (weight) g = the gravitational constant (6.672 x 10-11 N · m2 · kg-2) m1 = the mass of the object m2 = the mass of the Earth r = the distance between the object and the center of the Earth

  15. Weight varies due to three factors 1. Altitude As altitude increases r increases, so F decreases

  16. 2. Latitude Weight varies due to three factors

  17. Weight varies due to three factors 3. Local variations in rock density

  18. Geographic Survey of India Mid-19th century Sir George Everest Triangulation systematically disagreed with astronomical near the Himalayas Why?

  19. Each block weighs 2 g density 0.3 0.3 = 0.1 0.5 0.5 0.2 0.2 Water density 1.0 Archdeacon Pratt’s theory of Isostasy

  20. Wood density 0.5 8 g 5 g 5 g 3 g 3 g 2 g 2 g Water density 1.0 Each block weighs 2 g density 0.3 0.3 = 0.1 0.5 0.5 0.2 0.2 Water density 1.0 Astronomer Royal Airy’s theory of Isostasy

  21. Free-Air correction to 0 ft. Uncorrected gravity profile at 20,000 ft. Bouguer Corrected profile

  22. Free-air and Bouguer gravity anomaly map of the Alps

  23. Isostasy and Erosion