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SOURCE/RECEIVER SPACINGS AND THEIR INFLUENCE ON TOMOGRAMS

SOURCE/RECEIVER SPACINGS AND THEIR INFLUENCE ON TOMOGRAMS. Zhiyong Jiang. Geology and Geophysics Department University of Utah. Outline. Motivation Forward Modeling Refraction Tomography Optimal S/R Spacings Conclusions. Goal: Find the Optimal S/R Spacings. Interfaces. 220.

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SOURCE/RECEIVER SPACINGS AND THEIR INFLUENCE ON TOMOGRAMS

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  1. SOURCE/RECEIVER SPACINGS AND THEIR INFLUENCE ON TOMOGRAMS Zhiyong Jiang Geology and Geophysics Department University of Utah

  2. Outline • Motivation • Forward Modeling • Refraction Tomography • Optimal S/R Spacings • Conclusions

  3. Goal: Find the Optimal S/R Spacings Interfaces 220 Elevation (m) 130 X (m) 3290m 3360m

  4. INCO Velocity Model 0m V (m/s) 4500 Depth (m) 0 100m X (m) 0m 590m

  5. Outline • Motivation • Forward Modeling • Refraction Tomography • Optimal S/R Spacings • Conclusions

  6. Source at (200m, 3.003m) Source at (400m, 0.427m) 0 Time (s) 0.3 0 590 0 590 X (m) X (m)

  7. First Arrivals Auto Picked 0 Time (s) 0.15 0 590 X (m)

  8. Outline • Motivation • Forward Modeling • Refraction Tomography • Optimal S/R Spacings • Conclusions

  9. Smoothing Size (in grid points) Iterations Grid Size (m) Schedule 1: 48*24 11 0.5 Schedule 2: 32*16 11 0.5 Schedule 3: 16*8 11 0.5 Dynamic Smoothing The schedules for dg=4m and ds=8m

  10. dg=4m, ds=8m Schedule 1 0m V (m/s) 4500 0 120m 0m 590m

  11. dg=4m, ds=8m Schedule 2 0m V (m/s) 4500 0 120m 0m 590m

  12. dg=4m, ds=8m Schedule 3 0m V (m/s) 4500 0 120m 0m 590m

  13. dg=4m, ds=8m Schedule 1 0m Num. of Rays 4000 0 120m 0m 590m

  14. dg=4m, ds=8m Schedule 2 0m Num. of Rays 4000 0 120m 0m 590m

  15. dg=4m, ds=8m Schedule 3 0m Num. of Rays 4000 0 120m 0m 590m

  16. Sche 1 Sche 2 Sche 3 Residual vs. Iteration Number 0.014 Residual 0 0 35 Iteration Number

  17. Outline • Motivation • Forward Modeling • Refraction Tomography • Optimal S/R Spacings • Conclusions

  18. dg (m) ds (m) 1 2, 4 2 2, 4 4 4, 8 8 8, 16 12 12, 24 24 24, 48 S/R Spacings Tested

  19. dg=1m, ds=2m 0m 120m 0m 590m

  20. dg=1m, ds=4m 0m 120m 0m 590m

  21. dg=2m, ds=2m 0m 120m 0m 590m

  22. dg=2m, ds=4m 0m 120m 0m 590m

  23. dg=4m, ds=4m 0m 120m 0m 590m

  24. dg=8m, ds=8m 0m 120m 0m 590m

  25. dg=12m, ds=12m 0m 120m 0m 590m

  26. dg=12m, ds=24m 0m 120m 0m 590m

  27. dg=24m, ds=24m 0m 120m 0m 590m

  28. dg=24m, ds=48m 0m 120m 0m 590m

  29. dg (m) ds (m) 1 2, 4 2 2, 4 High Res. 4 4, 8 8 8, 16 12 12, 24 Intermediate Res. 24 24, 48 Poor Res. S/R Spacings Categorized

  30. dg=2m, ds=2m High Res. 0m 120m 0m 590m

  31. dg=12m, ds=12 m Interm Res. 0m 120m 0m 590m

  32. dg=24m, ds=24m Poor Res. 0m 120m 0m 590m

  33. Zoom View, X: 0~200m

  34. dg=2m, ds=2m High Res. 0m 120m 0m 200m

  35. dg=12m, ds=12m Interm Res. 0m 120m 0m 200m

  36. dg=24m, ds=24m Poor Res. 0m 120m 0m 200m

  37. Zoom View, X: 200~400m

  38. dg=2m, ds=2m High Res. 0m 120m 200m 400m

  39. dg=12m, ds=12m Interm Res. 0m 120m 200m 400m

  40. dg=24m, ds=24m Poor Res. 0m 120m 200m 400m

  41. Zoom View, X 400m~590m

  42. dg=2m, ds=2m High Res. 0m 120m 400m 590m

  43. dg=12m, ds=12m Interm Res. 0m 120m 400m 590m

  44. dg=24m, ds=24m Poor Res. 0m 120m 400m 590m

  45. Outline • Motivation • Forward Modeling • Refraction Tomography • Optimal S/R Spacings • Conclusions

  46. When ds, dg <= 12m, tomograms acceptable, resolution high When ds, dg > 24m, resolution very poor Recommend using ds, dg between 1~4 m for good vertical and horizontal resolution Conclusion

  47. Acknowledgements We thank Utah Tomography and Modeling/Migration Consortium sponsors for their financial support

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