I introduce a prestack generalization of exploding-reflectors modeling that has the potential to drastically reduce the computational cost of Migration Velocity Analysis (MVA) based on wavefield-continuation migration and modeling. The method aims at synthesizing, starting form a prestack migrated image, a limited number of independent experiments that contain all the velocity information needed for MVA.
The basic element of the method is the modeling of one isolated Subsurface-Offset Domain Common Image Gather (SODCIG) by using the prestack image as an initial condition. Taking advantage of the limited range of the subsurface offsets in the migrated image, we can combine many SODCIGs in the same modeling experiment without diminishing the velocity information contained in the data. The number of independent experiments required depends on how close we are to the correct migration velocity. In principle, this number is the same as the number of subsurface offsets needed to represent the prestack image from which we started the modeling. Several numerical examples illustrate the basic concepts of the proposed method, and demonstrate its potential usefulness for MVA.