Passive seismic imaging applied to synthetic data |
Cole (1995) tested this conjecture on both synthetic and real data. However his field data was very noisy, and he did not draw any solid conclusions.
With this as a starting point, however, I continued modeling a single
reflection, using a program based on the flow
loop over each plane wave {
calculate a random slowness,
calculate the time delay due to a reflection,
loop over each frequency, {
calculate a random amplitude
loop over each spatial location, x {
multiply each frequency by a factor
}
}
}
Having produced synthetics, it was then possible to go ahead and cross-correlate traces to try and create pseudo-reflection seismograms. Figure 3 is a pseudo-shot gather generated by cross-correlating one trace with every other. The center panel shows how the clarity of the signal was improved by applying a filter. The black line which has been overlain in the left panel corresponds to the expected hyperbola which would be observed in a real shot gather, offset by 0.05 s so it does not obscure the data. Therefore the kinematics in this case appear to be consistent with the conjecture.
first
Figure 3. Pseudo-shot gather over model with single horizontal layer and 200 incoming plane waves. The left panel is raw cross-correlations, the center panel has a half differentiation filter applied and the right panel is labeled with the correct kinematics shifted by 0.05 s. |
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Passive seismic imaging applied to synthetic data |