Essentially in this method, elastic properties of the geological subsurface are estimated. The method is carried out by minimizing the difference between simulated and recorded data. Hence, forward modeling is central in inversion & residual carried forth the iterative estimation process.
In this method, reflectivity of the geological boundaries is estimated by extrapolating the source and reflected wavefields into the subsurface using prespecified velocity model.
In the standard practice of migration, forward modelling of reflections is not done, neither is a residual calculated.