Hybrid Velocity Model Prestack Imaging

Abstract

Deep-water marine seismic data often suffer from non-hyperbolic moveout distortions generated by highly variable seafloor topography. The non-hyperbolic moveout is a result of lateral velocity variations across the rugose/dipping water bottom. Time migration assumes no lateral velocity variations and hence is unable to deal with these variations. The result of using a time migration algorithm is both a substandard image and perhaps more importantly, significant lateral movement of events. To overcome this limitation a hybrid depth migration coupled with a time velocity model building procedure is proposed. With this procedure the non-hyperbolic moveout distortions caused by highly variable seafloors are accounted for. The only cost is in the added expense of running a Pre-Stack Depth algorithm rather than a Pre-Stack Time algorithm. The model building effort is comparable.