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Optimal Source-Receiver Spacings for Improved Tomograms in Geophysical Exploration

This study by Zhiyong Jiang at the University of Utah explores the influence of source-receiver spacings on tomograms using refraction tomography. The research aims to find the best spacings for accurate imaging of subsurface interfaces in geophysical exploration. The results reveal that spacings between 1-4 meters provide good resolution, while spacings above 24 meters result in poor quality tomograms. By optimizing spacings, both vertical and horizontal resolution can be enhanced in geological imaging. The study recommends using spacings within the 1-4 meter range for optimal results in subsurface mapping.

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Optimal Source-Receiver Spacings for Improved Tomograms in Geophysical Exploration

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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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