SURFACE WAVE ELIMINATION BY INTERFEROMETRY AND ADAPTIVE SUBTRACTION YANWEI XUE University of Utah

Outline Surface Wave Problem & Remedy Surface Wave Problem & Remedy Theory of Interferometric Filtering Theory of Interferometric Filtering 2D Field Data Results 2D Field Data Results 3D Field Data Results 3D Field Data Results Conclusions Conclusions

d Time (s) Receiver (m) A seismogram with surface waves and reflections 0 Problem: Surface waves blur the seismograms. d surf Surface waves =+ d ref Reflection waves Solution: Filter the surface waves by Non- Linear Filter (NLF) and interferometric method

Outline Surface Wave Problem & Remedy Surface Wave Problem & Remedy Theory of Interferometric Prediction Theory of Interferometric Prediction 2D Field Data Results 2D Field Data Results 3D Field Data Results 3D Field Data Results Conclusions Conclusions

Prediction of Surface Waves Near-Offset Surf. Wave A B Mid-Offset Surf. Wave AB Near-Offset Surf. Wave A B A B AB A B A B

Basic Strategy Surface waves are removed completely? No Input data d d Output data Yesr Interferometric prediction ^ s^ s ^^d Least squares subtraction ^ ^ ^

Time (s) Receiver (m) Nonlinear Local Filter

Outline Surface Wave Problem & Remedy Surface Wave Problem & Remedy Theory of Interferometric Filtering Theory of Interferometric Filtering 2D Field Data Results 2D Field Data Results 3D Field Data Results 3D Field Data Results Conclusions Conclusions

Time (s) Receiver (m) Raw Data

Remove Surface Waves by NLF Time (s) Receiver (m)

Remove Surface Waves by Int.+NLF Time (s) Receiver (m)

Time (s) Receiver (m) Raw Data

Time (s) Receiver (m) Remove Surface Waves by F-K

Remove Surface Waves by Int.+NLF Time (s) Receiver (m)

Time (s) Receiver (m) Surface Waves Predicted by F-K

Surface Waves Predicted by Int.+NLF Time (s) Receiver (m)

Outline Surface Wave Problem & Remedy Surface Wave Problem & Remedy Theory of Interferometric Filtering Theory of Interferometric Filtering 2D Field Data Results 2D Field Data Results 3D Field Data Results 3D Field Data Results Conclusions Conclusions

Line 9 Before and After Removal of Surface Waves 04.0 Time (s) Receiver(m) Receiver (m)04.0 Time (s) Receiver (m)

Line 11 Before and After Removal of Surface Waves 04.0 Time (s) Receiver (m) 04.0 Time (s) Receiver (m)

Line 13 Before and After Removal of Surface Waves 04.0 Time (s) Receiver (m) 04.0 Time (s) Receiver (m)

Line 14 Before and After Removal of Surface Waves Time (s) Receiver (m) Time (s) Receiver (m)

Outline Surface Wave Problem & Remedy Surface Wave Problem & Remedy Theory of Interferometric Filtering Theory of Interferometric Filtering 2D Field Data Results 2D Field Data Results 3D Field Data Results 3D Field Data Results Conclusions Conclusions

Conclusions This approach is effective for surface wave removal in both 2D and 3D cases.This approach is effective for surface wave removal in both 2D and 3D cases. Advantages:Advantages: Limitations:Limitations: Better than FK method for irregular acquisition geometry.Better than FK method for irregular acquisition geometry. No need for a near surface velocity model.No need for a near surface velocity model. Sensitive to the choice of NLF parameters.Sensitive to the choice of NLF parameters. Parameter selection can be expensive.Parameter selection can be expensive. Future Work:Future Work: Eliminate need for non-linear local filter.Eliminate need for non-linear local filter. More tests on 3D data.More tests on 3D data.

Acknowledgement I thank the sponsors of 2006 UTAM consortium for their financial support.

THANKS!