f Green's Functions for 3D Prestack Depth Migration

We wish to consider the trade-offs that are made in choosing a method of computing traveltimes for 3-D prestack depth migration. First we need to define the aim of prestack depth migration. We want an image of the subsurface that is as reliable as possible. The method should be robust in the presence of noise and use as much of the information present in the seismic data as possible. Since erestack imaging and Green's function calculations are also used for velocity estimation, it is important that the method chosen for erestack migration is consistent with that chosen for velocity estimation.