1 / 25

Seismic refraction method

Seismic refraction method. Snell's law sin(i p )/  1 = sin(i s )/  1 = sin(r p )/  2 = sin(r s )/  2 = p, the ray parameter. Ray paths in 1 layer. Note V 1 > V 0 required for head wave. Waves in a 1 layer* model: V 1 < V 0. * one layer above a halfspace. V 1 < V 0.

janetn
Download Presentation

Seismic refraction method

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. Seismic refraction method Snell's law sin(ip)/1 = sin(is)/1 = sin(rp)/2 = sin(rs)/2 = p, the ray parameter

  2. Ray paths in 1 layer Note V1 > V0 required for head wave

  3. Waves in a 1 layer* model: V1 < V0 * one layer above a halfspace V1 < V0

  4. The wavefield

  5. Waves in a 1 layer model: V1 > V0 V1 > V0

  6. Wavefield at 65 ms

  7. ... at 110 ms

  8. ... at 140 ms Direct, reflected, refracted and 'head' waves

  9. Refractions and reflections ...a ray model Snell's law in a 1-layer structure

  10. A seismic refraction survey

  11. First and later 'arrivals'

  12. A seismogram

  13. The 'spread'

  14. Travel-time curves

  15. Dipping layer?

  16. ... modified travel-times

  17. Down dip...

  18. Up dip...

  19. ... earlier head wave

  20. Two dipping layers...

  21. ... travel times

  22. A 2-layer survey

  23. The interpretation http://www.epa.gov/oust/pubs/esa-ch3.pdf

  24. Global refraction As seismic velocities generally increase with depth, the P-waves and S-waves are refracted back to the surface. We can interpret the travel-time curves as an infinite number of infinitesmally thin layers in spherical shells..

  25. Reference Some of the nice graphical images used in this presentation are taken from the seismic noteset: http://galitzin.mines.edu/INTROGP/MISC/seisnotes.pdf

More Related