Prestack depth migration has become almost mandatory in areas of complex geology for reasons that are abundantly clear. In structurally complex media, CMP traveltime curves differ significantly from hyperbolae. Thus, when using standard time-processing techniques, we cannot produce a time section containing all information related to the medium that is in the prestack gathers.

Depth migration has, in fact, quite a limited purpose—to convert seismic data from one form to another for a given velocity model. Possible variants of migration include conversion of a time section to a depth section (poststack depth migration) or of prestack gathers to a depth...

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