TARGET-ORIENTED LEAST SQUARES MIGRATION

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

• Least Squares Migration
• Target-Oriented LSM
• Numerical Examples
• Conclusions

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Standard Migration
LSM
dLm
dLm
mmigLTd
mmigLTL-1LTd
d observed data m reflectivity model
L forward operator mmig migration image
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A Simple Model
Distance (km)
1
0
0
Depth (Km)
1.2
True Reflectivity Model
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Migration Results
Distance (km)
Distance (km)
1
0
1
0
0
0
Depth (Km)
Depth (Km)
1.2
1.2
LSM-20
Standard Migration
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Limitation of LSM

• 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

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Outline

• Least Squares Migration
• Target-Oriented LSM
• Numerical Examples
• Conclusions

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Target-Oriented LSM
LSM
Data
Model
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Outline

• Least Squares Migration
• Target-Oriented LSM
• Numerical Results
• Conclusions

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Unocal Poststack Data
Distance (km)
14.4
0
0
Depth (Km)
1.5
Standard Migration
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Unocal Poststack Data
Distance (km)
14.4
0
0
Depth (Km)
1.5
LSM-40
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Unocal Poststack Data
Distance (km)
14.4
0
0
Depth (Km)
1.5
LSM-80
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Unocal Poststack Data
Distance (km)
14.4
0
0
Depth (Km)
1.5
MD
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Target-Oriented LSM
Distance (km)
0
14.4
a
0.8
D (Km)
1.5
b
0.8
D (Km)
1.5
(a) Standard Migration (b) LSM-5
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Target-Oriented LSM
Distance (km)
0
14.4
a
0.8
D (Km)
1.5
b
0.8
D (Km)
1.5
(a) Standard Migration (b) LSM-10
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Outline

• Least Squares Migration
• Target-Oriented LSM
• Numerical Results
• Conclusions

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Conclusion

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

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Future Work

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

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