Anatomy of common scatterpoint (CSP) gathers formed during equivalent offset prestack migration (EOM)

John C. Bancroft, Hugh D. Geiger

The equivalent offset method of prestack migration (EOM) is a two step process: the first being a gathering process that forms common scatter point (CSP) gathers, and the second a simplified Kirchhoff NMO to zero offset performed on the CSP gathers.

CSP gathers contain a greater amount of information than conventional CMP gathers because they contain all input traces within the prestack migration aperture. These traces are sorted by an equivalent offset into bins in the CSP gather with no time shifting. The energy from these traces, which is typically associated with CMP gathers and poststack migration, is now combined into one CSP gather to produce a compounded distribution of energy. Understanding the distribution of energy on the CSP gather is essential to define parameters for a successful prestack migration.