1. TARGET-ORIENTED LEAST SQUARES MIGRATION Zhiyong Jiang Geology and Geophysics Department University of Utah

2. Outline Least Squares Migration Least Squares Migration Target-Oriented LSM Target-Oriented LSM Numerical Examples Numerical Examples Conclusions Conclusions

3. Standard Migration d=Lm d=Lm m mig =[L T L] -1 L T d LSM d=Lm d=Lm m mig =L T d d : observed data m : reflectivity model L : forward operator m mig : migration image

4. A Simple Model True Reflectivity Model 0 1 Distance (km) 0 1.2 Depth (Km)

5. Migration Results Standard Migration LSM-20 0 1 Distance (km) 0 1.2 Depth (Km) Distance (km) 0 1 0 Depth (Km) 1.2

6. Limitation of LSM Requires 10 or more iterations,where each iteration requires several forward modeling and several migration steps Requires 10 or more iterations,where each iteration requires several forward modeling and several migration steps Impractical to implement for current 3-D prestack imaging of large data sets Impractical to implement for current 3-D prestack imaging of large data sets

7. Outline Least Squares Migration Least Squares Migration Target-Oriented LSM Target-Oriented LSM Numerical Examples Numerical Examples Conclusions Conclusions

8. Target-Oriented LSM LSM Data Model

9. Outline Least Squares Migration Least Squares Migration Target-Oriented LSM Target-Oriented LSM Numerical Results Numerical Results Conclusions Conclusions

10. Standard Migration Unocal Poststack Data 0 14.4 0 1.5 Distance (km) Depth (Km)

11. LSM-40 Unocal Poststack Data 0 14.4 0 1.5 Distance (km) Depth (Km)

12. LSM-80 Unocal Poststack Data 0 14.4 0 1.5 Distance (km) Depth (Km)

13. MD Unocal Poststack Data 0 14.4 0 1.5 Distance (km) Depth (Km)

14. Target-Oriented LSM (a) Standard Migration (b) LSM-5 a b 014.4 0.8 1.5 0.8 1.5 D (Km) Distance (km)

15. Target-Oriented LSM (a) Standard Migration (b) LSM-10 a b 014.4 0.8 1.5 0.8 1.5 D (Km) Distance (km)

16. Outline Least Squares Migration Least Squares Migration Target-Oriented LSM Target-Oriented LSM Numerical Results Numerical Results Conclusions Conclusions

17. Conclusion LSM is effective in suppressing the migration artifacts, but expensive LSM is effective in suppressing the migration artifacts, but expensive Target-oriented LSM improves the image quality in a few iterations Target-oriented LSM improves the image quality in a few iterations Target-oriented LSM greatly reduces CPU time Target-oriented LSM greatly reduces CPU time

18. Future Work How to better define the target data box How to better define the target data box Test the target-oriented LSM on prestack data Test the target-oriented LSM on prestack data Implement MD filter as a preconditioner to LSM Implement MD filter as a preconditioner to LSM

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