Prestack migration to an unmigrated zero offset section

Hugh D. Geiger, John C. Bancroft

The process of prestack migration of a 2D seismic data set using equivalent offset and CSP gathers creates an intermediate collection of traces - the CSP gather - that can easily be sorted and stacked to create an unmigrated section. Creation of the unmigrated section is insensitive to velocity except at steep dips. Thus the unmigrated equivalent offset section may be the ideal brute stack. In the process of full prestack time migration using the equivalent offset method, the unmigrated stack is useful for the identification of seismic events and structure for velocity analysis.

An unmigrated stack of a portion of the Marmousi model created with a single velocity function compares well with the best unmigrated section created by one of the original Marmousi participants.