The last imaging operator that I describe is prestack depth migration. An ideal case would be to use a two-way wave-propagation operator, such as reverse-time migration or elastic wave-equation migration. These processes are very expensive and not yet practical for most data sizes. As an approximation to this process, I present an acoustic prestack wave-equation-based migration operator, using two propagation velocities, a P-velocity to propagate the source function and an S-velocity to propagate the receiver function. This approximation is valid, since the source for an OBS acquisition is acoustic, and I use the approximation that the elastic components of the seismic wavefield are produced at the reflections.
Chapter 2 describes the basic problems for imaging PS data. I conclude that the ideal domain to address most of the problems for PS imaging, is composed of depth, image-midpoint location, and subsurface offset.