Iteration with CMP-stacked data

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Seismic Data Analysis
Seismic-data-analysis.jpg
Series Investigations in Geophysics
Author Öz Yilmaz
DOI http://dx.doi.org/10.1190/1.9781560801580
ISBN ISBN 978-1-56080-094-1
Store SEG Online Store


Depth migration of the CMP-stacked section in Figure 8.2-1 using Model A required two iterations to achieve convergence (Figure 8.2-21). The resulting image and the model inferred from it have some inaccuracies. It appears that starting with the true model (Model A), iterative poststack depth migration does not exactly reproduce the true model. For the zero-offset section, starting with the true model, convergence was achieved after one iteration and the resulting model was the same as the input model (Figure 8.2-11). Again, the reason for the less-than-ideal performance of poststack depth migration is that the CMP stack is only an approximation to the zero-offset wavefield. The more the stacked section departs from the zero-offset wavefield, the more the final model will depart from the true model.

Now consider Model D in Figure 8.2-22 in which the salt velocity and the base-salt boundary are incorrectly specified. After the third iteration with the stacked section, we find that convergence is achieved. Nevertheless, the final solution has converged to a velocity-depth model that is different from the true model.

If the initial model contains errors in reflector geometries only, and layer velocities are specified correctly, then convergence using the stacked section to the true velocity-depth model is nearly achievable (Figure 8.2-23).

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Iteration with CMP-stacked data
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