1. Fresnel-zone Traveltime Tomo. for INCO and Mapleton Data Fresnel-zone Traveltime Tomo. for INCO and Mapleton Data Jianming Sheng University of Utah Feb. 5, 2004

2. Motivation Ray-based Traveltime Tomo. Biased towards high-velocities High-frequency assumption

3. Ray Distribution 045 080 Depth (m) Distances (m) 8000 4000 0 6000 2000

4. Motivation Ray-based Traveltime Tomo. Biased towards high-velocities High-frequency assumption Solution 1: Wavepath traveltime tomo. Bandlimited, unbiased, multipath Wave-equation Solution 2: Fresnel-zone traveltime tomo. Paraxial ray approximation

5. Wavepath or Fresnel-zone s g Fresnel Zone x

6. First-break and first-peak Tomo. Outline Mapleton Data Summary INCO Synthetic Data

7. Principlesg First-break: high velocity First-peak: diffraction stacking First-arrivals result from First-arrivals result from diffraction stacking diffraction stacking

8. Misfit Function { { First-peakFirst-break

9. Fresnel-zone Traveltime Vasco et al. (1995) sg My Quick and dirty way: dirty way: t shift W(t)

10. Sensitivity Function (first-peak) Rytov Approx. (Woodward, 1992) Phaseresidual Slowness Geometricalspreading sg x t sg t sxg

11. Backprojecting First-break Res. 45 080 Depth (m) Distances (m) 4000 0 6000 20000 045 Depth (m) 2500 500 m/s 0 80 0 80045 2500 500 m/s 0 80 0 80 s g Smoothing along a fat-ray

12. First-break and first-peak Tomo. Outline Mapleton Data Summary INCO Synthetic Data

13. INCO Synthetic Model 080 Depth (m) X (m) 45003500 2500 1500 m/s 0590

14. INCO Synthetic Data 0 0.15 Time (sec.) 296 shots (2m) 591 rec. (1m) Dt: 0.05 ms Length: 0.3s 200 400 X (m) Freq.: 90Hz Zhiyong Jiang

15. INCO Synthetic Model 080 Depth (m) X (m) 45003500 2500 1500 m/s 0590 V=900 m/s L=10 m L=16.7 m V=1500 m/s V=2500 m/s L=28 m V=4500 m/s L=50 m

16. Ray-based Tomogram 080 Depth (m) X (m) 45003500 2500 1500 m/s 0590

17. INCO Synthetic Model 080 Depth (m) X (m) 45003500 2500 1500 m/s 0590 10 m 16.7 m 28 m 50 m

18. Fat-Ray Tomogram 080 Depth (m) X (m) 45003500 2500 1500 m/s 0590

19. First-break and first-peak Tomo. Outline Mapleton Data Summary INCO Synthetic Data

20. Mapleton, Utah Data 0 0.15 Time (sec.) 20160 168 shots 168 receiver Interval: 5m dt: 0.5 ms length: 1s

21. First-break Fat-ray Tomo. 0 45 Depth (m) 2500 500 m/s 080 Distances (m)

22. First-break + First-peak 0 45 Depth (m) 2500 500 m/s 080 Distances (m)

23. Migration Image 0 45 Depth (m) 300 080 Distances (m) 200 100 0 100 -200

24. First-break and first-peak Tomo. Outline Mapleton Data Summary INCO Synthetic Data

25. Summary A first-break and first-peak tomo. is designed. A first-break and first-peak tomo. is designed. Mapleton Data: Mapleton Data: INCO Synthetic data: INCO Synthetic data: Fat-ray tomo. provides a better tomogram This method can image complex models; More tests are necessary.

26. Acknowledgment I thank the sponsors of the 2003 UTAM Consortium for their financial support.