Interferometric Extraction of SSP from Passive Seismic Data Yanwei Xue Feb. 7, 2008
OUTLINE Motivation Theory Field data test Conclusions and the way ahead
Motivation No individual experiment required Can get Green’s function between two randomly selected receivers Why? How? Interferometric Transform
OUTLINE Motivation Theory Field data test Conclusions and the way ahead
Random Sources =δ(x-x’)S(ω) =δ(x-x’)S(ω) P(B) = P(B) = ∫ G(B|x)N(x)d x 2 S src Im[G(A|B)] = k Im[G(A|B)] = k = k = k ∫ G(B|x)G(A|x)*d x2 S src A B..S0 S src x x’ z
Random Scatterers
Workflow Input data d Truncate d in time into several data panels Truncate d in time into several data panels Crosscorrelate each trace with a given trace at x Crosscorrelate each trace with a given trace at x Sum and average the crosscorrelation panels Sum and average the crosscorrelation panels Output
OUTLINE Motivation Theory Field data test Conclusion and the way ahead
Data Introduction 8 receiver lines 779 receivers Receiver interval: m X (m) Y (m) Receiver position
Amplitude Time (s)0960 Trace Example
Virtual Shot Gather Receiver line 6 90 receivers Frequency used to do the interferometry is Hz Event velocity 1450 m/s Time (s) X (m)
Time (s) X (m) Receiver line 6 90 receivers Frequency used: 1 – 9 Hz Event velocity 1450 m/s Virtual Shot Gather
Time (s) X (m) Receiver line 8 95 receivers Frequency used: Hz Event velocity 1455 m/s
Time (s) X (m) Virtual Shot Gather Receiver line 2 90 receivers Frequency used: Hz
Receiver line 2 90 receivers Frequency used: Hz Left-going events removed Time (s) X (m) Virtual Shot Gather
OUTLINE Introduction Theory Field data test Conclusions and the way ahead
Conclusions Field data test gives continuous events Low frequency results have a velocity of 1450 m/s High frequency ( Hz) results look like reflections We need records with longer time to get better results
Road Ahead Test the data with longer time records Velocity analysis of the virtual gathers Migrate the virtual data
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