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Imaging via Subgrid Upscaling and Reverse Time Migration

Reverse time migration produces an image by crosscorrelating the solution of the wave equation solved forward in time with the wave equation solved backwards in time. Solution of the wave equation can be computationally prohibitive for large subsurface regions. Therefore one typically combines a finite difference discretization of the wave equation with a parallel computing paradigm such as domain decomposition. Operator or subgrid upscaling is an alternate technique which produces a coarse scale solution of the wave equation that captures fine scale information. In the computationally intensive part of the algorithm one achieves ideal speedup without ghost cell allocation or communication. In this work we show the first images from reverse time migration (RTM) combined with operator upscaling. These upscaled images capture essentially the same velocity heterogeneities as RTM using the full fine grid solution.