1. Interferometric Traveltime Tomography M. Zhou & G.T. Schuster Geology and Geophysics Department University of Utah

2. Interferometry In Phase Out of Phase oil Film

3. Interferometry

4. Outline Objective Objective Interferometry Methodology Interferometry Methodology Numerical Results Numerical Results Refraction Data Refraction Data Crosswell Data Crosswell Data Conclusions Conclusions

5. Objective Eliminate Shot / Receiver Eliminate Shot / Receiver Static Errors in Seismic Data Static Errors in Seismic Data

6. Outline Objective Objective Interferometry Methodology Interferometry Methodology Numerical Results Numerical Results Conclusions Conclusions

7. Methodology  t ij = (t i - t j ) obs - (t i - t j ) cal - (t i - t j ) cal Standard Tomography Interferometric Tomography Smear residual  t i along raypath t i obs  t i = t i obs - t i cal Smear residual  t ij along raypaths t j obs t i obs

8. Why Interferometry?  t ij = (t i - t j ) obs - (t i - t j ) cal t i ’ =t i+  t t j ’ =t j+  t tttt Source timing error Eliminate the source timing error

9.  t ij = (t i - t j ) obs - (t i - t j ) cal t j ’ =t j+  t tttt Receiver-timing error t i ’ =t i+  t Eliminate the receiver timing error

10.  t =  t 1 +  t 2 +  t 3 = t 11 - t 12 + t 23 - t 21 + t 32 - t 33 t 11 ’ =t 11+  t s1+  t r1  t s1  t r1  t s2  t r3  t r2  t s3  t 1 = t 11 - t 12 +  t r1 -  t r2 t 11 t 12 ’ =t 12+  t s1+  t r2  t 2 = t 23 - t 21 +  t r3 -  t r1  t 3 = t 32 - t 33 +  t r2 -  t r3 “Phase closure“ Theorem Eliminate both the source and receiver timing errors

11. ITT Can Eliminate source and receiver static errors

12. Problem with ITT Smear residual  t ij along raypaths  t ij = (t i - t j ) - (t i - t j ) cal tjtjtjtj titititi Lose Resolution

13. Outline Objective Objective Methodology Methodology Numerical Results Numerical Results Synthetic Refraction Data Synthetic Refraction Data Synthetic Crosswell Data Synthetic Crosswell Data Little Cottonwood Field Data Little Cottonwood Field Data Kidd Creek Crosswell Data Kidd Creek Crosswell Data Conclusions Conclusions

14. Surface-refraction Experiment Synthetic Model Depth (m) 0 100 5000 km/sec 4 2 1 3 Offset (m) Shot/receiver interval 2 m No. of shots/receivers 251 Master trace

15. Inversion Results (Refraction Data) b) Standard Method km/sec4 1 2 3 Offset (m) d) ITT + timing shifts km/sec4 2 3 1 0500 100 a) Synthetic model Depth (m) 0 20 40 c) Standard + timing shifts Depth (m) Offset (m) 0 100 0500 20 40

16. Outline Objective Objective Methodology Methodology Numerical Results Numerical Results Synthetic Refraction Data Synthetic Refraction Data Synthetic Crosswell Data Synthetic Crosswell Data Little Cottonwood Field Data Little Cottonwood Field Data Kidd Creek Crosswell Data Kidd Creek Crosswell Data ConclusionsConclusions

17. Crosswell Experiment Shot/receiver interval 4 m No. of shots/receivers 301 Synthetic Model Depth (m) 0 1200 500 0 km/sec 4.5 4.0 3.5 3.0 Offset (m) 400 600 Master trace

18. Inversion Results (Crosswell Data) a) Synthetic model Depth (m) 0 1200 c) Standard + shifts Depth (m) Offset (m) 0 1200 0500 b) Standard Method km/sec4.5 3.0 3.5 4.0 d) ITT + shifts Offset (m) 0500km/sec4.5 3.0 3.5 4.0

19. Outline Objective Objective Methodology Methodology Numerical Results Numerical Results Synthetic Refraction Data Synthetic Refraction Data Synthetic Crosswell Data Synthetic Crosswell Data Little Cottonwood Field Data Little Cottonwood Field Data Kidd Creek Crosswell Data Kidd Creek Crosswell Data Conclusions Conclusions

20. Recording Geometry 12 3 48 97 144 Shot / geophone Ground Surface 56.71 feet 214.5 feet Shot / geophone interval 1.5 feet No. of shots / geophones 144

21. Inversion Results a) Standard method Depth (ft) 0 150 c) Standard + timing shifts Depth (ft) Offset (ft) 0 150 0200 0 1 2 b) ITT kft/sec 0 d) ITT + timing shifts Offset (ft) 200 0 1 2kft/sec

22. Outline Objective Objective Methodology Methodology Numerical Results Numerical Results Synthetic Refraction Data Synthetic Refraction Data Synthetic Crosswell Data Synthetic Crosswell Data Little Cottonwood Field Data Little Cottonwood Field Data Kidd Creek Crosswell Data Kidd Creek Crosswell Data Conclusions Conclusions

23. Recording Geometry Y (km) 65.7765.78 Source Hole Receiver Hole X (km) Z (km) 1.09 65.81 65.74 1.12

24. Inversion Results Offset (m) b) Standard 050 7.0km/sec8.0 6.0 9.0 Ore body km/sec5.0 7.0 a) ITT Depth (m) Offset (m) 0 30 60 050 Source hole receiver hole 6.0 Ore body

25. Inversion Results a) Standard + 3.5 ms Depth (m) Offset (m) 0 30 60 050 Source hole receiver hole Ore body b) ITT Offset (m) km/sec050 6.0 5.0 7.0

26. Outline Objective Objective Methodology Methodology Numerical Results Numerical Results Conclusions Conclusions

27. Conclusions ITT is effective and stable in eliminating ITT is effective and stable in eliminating shot-timing shifts, shot-timing shifts, At the cost of reduced model resolution At the cost of reduced model resolution

28. Future Work Improve slowness resolutionImprove slowness resolution Recover the DC componentRecover the DC component Regularization Methods Regularization Methods Develop ‘Phase Closure’ for CDP Data Eliminate source- and receiver-Eliminate source- and receiver- static errors simultaneously static errors simultaneously

29. Acknowledgements I am grateful for the financial I am grateful for the financial support from the members of support from the members of the 1999 UTAM consortium. the 1999 UTAM consortium.