DMO and NMO as applied in seismic data processing

Abstract

DMO (dip-moveout) is recognized as the technique to image the steep dip events which are indiscriminately smeared when the data are processed with the conventional seismic imaging method, which includes NMO, CMP stacking and zero offset migration. From these published papers, we may find many ways to do DMO, such as prestack partial migration, DMO by Fourier transform, offset continuation, single channel DMO ... etc, and the improvements of these techniques are widely recognized. But every technique is available only in two-dimensional case. To extend DMO to 3D (three dimensional) case, those techniques operating on constant offset section are generally available only when the feathering angle can be constrained within a very small value, but this condition is really hard to be achieved when the sea current is rough. In this paper the author is going to extend the Rocca's smile operator into 3D case, so that an easy way of doing DMO will be available to any 3D data. A further consideration is also given to mixing the NMO with the DMO in this paper. The reason for doing this is not only to simplfy the process and to save computer time, but also to search for more accurate velocity information for the NMO correction when the dip angle is large. This technique will be very effective compared to sole DMO, when the velocity changes very rapidly with depth.