Increasing Illumination and Sensitivity of Reverse-time Migration with Internal Multiples

Reverse-time migration is a two-way time-domain finite-frequency technique that accurately handles the propagation of complex scattered waves and produces a band-limited high-frequency representation of the subsurface structure that is conventionally assumed to be linear in the model parameters. Because of this underlying linear single-scattering assumption, most implementations of this method paradoxically do not satisfy energy conservation and do not optimally use illumination and sensitivity of multiply scattered waves. Migrating multiply scattered waves requires preserving the nonlinear relation between image and model parameters. We modify the extrapolation of source and receiver wavefields to more accurately reconstruct multiply scattered waves. We extend the concept of imaging condition in order to map into the subsurface structurally coherent seismic events which correspond to the interaction of both singly and multiply scattered waves. This results in an imaging process that we refer to as nonlinear reverse-time migration. We propose a strategy to analyze separated contributions to the final nonlinear image. Our goal is to provide tools suitable for both interpretation and velocity analysis with multiply scattered seismic waves. We illustrate our technique with synthetic seismic imaging experiments.