Generalized Diffraction-stack Migration: A Modified Form of Reverse-time Migration

The two end members of migration algorithms are diffraction-stack migration and reverse-time migration (RTM). The former is computationally inexpensive, flexible, but subject to the high-frequency approximation of ray tracing. Consequently, it has difficulty with complex velocity models that preclude the accurate use of ray tracing. To overcome this limitation, reverse-time migration uses finite-difference solutions to the wave equation to accurately propagate seismic energy through complex models. But the price we pay is a computationally expensive algorithm that appears inflexible to efficiency improvements or algorithmic tricks that suppress migration noise such as obliquity and intrinsic antialiasing filters. In this chapter, I will first overview these two migration algorithms and then reformulate the equations of reverse-time migration, so that they can be reinterpreted as a generalized diffraction-stack migration algorithm, which can partly remediate these deficiencies of RTM.