Prestack depth migration velocity analysis: linear theory revised
, by John T. Etgen
A residual moveout correction applied to prestack-depth-migrated constant-
offset sections approximates remigrating the constant-offset sections with
a perturbed interval-slowness model. The residual moveout correction is
applied to each offset for all points in the migrated image, and a moveout
corrected stacked section is made for a range of residual slownesses. The
result constitutes the data space for an optimization problem that estimates
perturbations to the interval-slowness model that will result in the most
coherent migrated image. Changes in the interval-slowness model can be linearly
related to changes in the residual moveout curves that best approximate the
offset-stacking curves required to form the migrated image produced by the
perturbed interval-slowness model. The linear relation between changes in
the interval-slowness model and the best fitting residual moveout curves is
used to compute the gradient of the total coherence of the image with respect
to the interval-slowness model from the precomputed data space. An iterative
optimization alogrithm driven by this gradient will estimate the interval-
slowness model that produces the most coherent prestack depth migrated image
of the data.
STANFORD