1 / 49

Three Worlds to Explore

Look Up? (Astronomy). Three Worlds to Explore. Look at Surface? (Geology). Look Down? (Geophysics). The Earth ’ s Interior. Deep wells and boreholes (4 to 12 km). Astronomical Observations. The Earth: What ’ s it made of?. Gravity. Seismology. N. S. Magnetism. Heat Flow.

norm
Download Presentation

Three Worlds to Explore

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Look Up? (Astronomy) Three Worlds to Explore Look at Surface? (Geology) Look Down? (Geophysics)

  2. The Earth’s Interior Deep wells and boreholes (4 to 12 km)

  3. Astronomical Observations The Earth: What’s it made of? Gravity Seismology N S Magnetism Heat Flow

  4. Density of Water 1 gm/cm3 Crust 2.6-3.1 gm/cm3 Mantle 3.3-5.7 gm/cm3 Outer Core 10-12 gm/cm3 Inner Core 13-14 gm/cm3

  5. The primary “tool” for investigating the physical properties of the Earth’s interior isseismology. Seismology

  6. What is a Seismic Wave? Epicenter • Seismic waves are vibrations that travel through the Earth carrying the energy released during an earthquake. • Seismic waves travel outward in all directions, like ripples in a pond. Seismic Waves

  7. Seismology = The study of seismic waves. • Seismograph = Instrument that records seismic waves. • Seismogram = The record of ground motion that is produced by a seismograph.

  8. Two main groups of seismic waves. • Body waves travel through the Earth’s interior. • Surface waves are guided by the outer layers of the Earth.

  9. Two types of body waves. • P-waves = • Primary Waves = • first arrival • S-waves = • Secondary Waves = second arrival

  10. P-waves and S- waves are distinguished from each other by the way they propagate through the Earth. P-waves push (compress) and pull (dilate) rocks in the direction the wave is traveling.

  11. S-waves “shake” the material at right angles to their direction of travel.

  12. Slide courtesy of Seth Stein

  13. Slide courtesy of Seth Stein

  14. Slide courtesy of Seth Stein

  15. Slide courtesy of Seth Stein

  16. P-waves can travel through solids, liquids, and gases because matter in all three of these states resists being compressed and will elastically spring back once the force is removed. • S-waves can only travel through solids, because fluids do not resist shearing motion. So, fluids do not transmit S-waves.

  17. The Earth’s Interior Deep wells and boreholes (4 to 12 km)

  18. Two main groups of seismic waves. • Body waves travel through the Earth’s interior. • Surface waves are guided by the outer layers of the Earth.

  19. Two types of body waves. • P-waves = • Primary Waves = • first arrival • S-waves = • Secondary Waves = second arrival

  20. Two types of surface waves. • Rayleigh waves: Discovered by Lord Rayleigh (1887). • Love waves: Discovered by A.E.H. Love (1911).

  21. minutes hours days weeks months Slide courtesy of Seth Stein

  22. minutes hours days weeks months Slide courtesy of Seth Stein

  23. Data from station MBWA (Marble Bar, Western Australia) last updated at Thu 10/30/03 12:53 GMT

  24. Magnitude 7.1 Earthquake in Taiwan - December 26, 2006

  25. Magnitude 7.1 Earthquake in Taiwan - December 26, 2006

  26. Rayleigh Radial Love Transverse Rayleigh Vertical Slide courtesy of Seth Stein

  27. In the case of surface waves, the ground motion is concentrated near the surface of the Earth, and the wave motion is similar to that of water waves in the ocean.

  28. In the case of water waves, a particle of water (or a toy boat) at the surface moves in a circular pattern, but stays at the same location. At greater depth, the water particles also move in circles, but the circles are smaller.

  29. Rayleigh wave motion is similar to water wave motion, except that for Rayleigh waves, the circles are “retrograde”. < >

  30. Love waves have side-to-side ground motion, similar to S-waves, except that the ground motion decays with depth in a manner similar to Rayleigh waves and water waves.

  31. Granite (and Average Continental Crust) 6.0 km/sec 2.5 km/sec 3.5 km/sec 3.0 km/sec Differences in density and other physical properties affect the velocity of seismic waves.

  32. Oceanic Crust: P-wave Velocity = 7 km/sec “Basalt” Continental Crust: P-wave Velocity = 6 km/sec “Granite”

  33. Density of Water 1 gm/cm3 Crust 2.6-3.1 gm/cm3 Mantle 3.3-5.7 gm/cm3 Outer Core 10-12 gm/cm3 Inner Core 13-14 gm/cm3

  34. 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

More Related