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Time-reversal acoustics, virtual source imaging, and seismic interferometry

Time-reversal acoustics, virtual source imaging, and seismic interferometry. Haijiang Zhang University of Science and Technology of China. Time-reversal acoustics. Fink, 1997. Time-reversal and super resolution.

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Time-reversal acoustics, virtual source imaging, and seismic interferometry

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  1. Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China

  2. Time-reversal acoustics Fink, 1997

  3. Time-reversal and super resolution More heterogeneous and scattered the medium between the source and the TRM, the more focused the time-reversed signal.

  4. Time-reversed seismic location • No picking required • Automatic (real-time) location • Using full waveforms

  5. Virtual source method Sources Sk on the surface Receivers in the borehole The goal is to construct seismic record from virtual source to receivers. Bakulin and Calvert, 2006

  6. Synthetic velocity models

  7. Virtual source gather (at 900 m) Real source gather (at 900 m)

  8. Constructing virtual source (VS) data Bakulin and Calvert, 2006

  9. Applications Problem: Overburden+statics defocus VSP migration Solution: VSP -> SWP Transform (Calvert, Bakulin) VSP VSP SWP Redatum sources below overburden Local VSP migration Shuster, SEG 09

  10. 0 Reflection wavefield Time (s) 3 VSP Geometry 1500 Depth (m) 3500 Offset (m) 1000 0 (He , 2006)

  11. 0 Reflection wavefield Time (s) 3 VSP Geometry 1500 Depth (m) superresolution 3500 Offset (m) 1000 0 China (He , 2006)

  12. 120 shots ? 98 geophones Poor image of flank by standard migration VSP Salt Flank Imaging (Hornby & Yu, 2006) Overburden

  13. Interferometric Migration Result

  14. Seismic Interferometry • Interferometry is a family of techniques in which waves, are superimposedin order to extract information about the waves (from wikipedia). • Seismic Interferometry involves cross correlating and stacking diffusive waves to extract Green’s functions.

  15. Cross-correlation and stacking Gsa(t): Green’s function from source s to a. e(t): Source time function. Cross-correlation Stacking: source averaging

  16. Homogeneous medium • Circular sources • τ= -3T0 • τ= -T0 • Τ=10T0 Larose et al., 2005

  17. Homogeneous medium • 800 sources (partially covered) • τ= -3T0 • τ= -T0 • Τ=10T0

  18. Heterogeous medium 800 sources (partially covered) a) first-part coda b) late coda

  19. Time-reversal interpretation of the correlation process Treat a as the virtual source

  20. (Weaver and Lobkis, Ultrasonics, 40, 435-439, 2002)

  21. (Weaver and Lobkis, Ultrasonics, 40, 435-439, 2002)

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