C020 Model-Based Decimation of Input Data for P- Migration for the Purpose of Subsalt Velocity Model Building B. Wang* (CGGVeritas) F. Gao (CGGVeritas) D. Wheaton (CGGVeritas) & V. Dirks (CGGVeritas) SUMMARY The process of subsalt velocity model building often requires multiple prestack depth migration runs either for salt geometry scan or subsalt sediment velocity scan. Historically and from a practical point of view decimation of the input data using a regular or random pattern of data selection is frequently applied but does not make use of any available illumination criteria. In this paper we present an alternative methodology that offers