The AMO operator presented in this paper is a new partial prestack-migration operator that can be efficiently applied to 3-D prestack seismic data to transform their effective offset and azimuth. AMO is a generalization of the migration-to-zero-offset operators (e.g. DMO) because it can transform data to arbitrary offsets and azimuths.

To derive the AMO operator we cascaded a 3-D prestack imaging operator with a 3-D prestack modeling operator. We used both DMO cascaded with inverse DMO and constant-velocity full prestack migration cascaded with constant-velocity prestack modeling. The constant-velocity assumption is necessary to an analytical derivation of the AMO operator and theoretically limits its range of potential application, because propagation velocity in the Earth is not constant. However, as shown in this paper, the results of processing a marine data set demonstrate that AMO can be effectively applied to data that were acquired over complex structures and whose proper imaging requires 3-D prestack depth migration.

This paper showed that AMO can successfully achieve a considerable reduction in the computational cost of 3-D prestack depth imaging, without sacrificing the accuracy of the results. The application of AMO improves the accuracy of partial stacking 3-D data over a range of offsets. In particular, the high-frequency steeply-dipping components of the reflected, or diffracted, energy benefit from the application of AMO. These components are crucial for the correct interpretation of complex fault systems, as well as for high-resolution imaging of complex reservoirs.

11/11/1997