Conclusion

Fourier finite-difference (FFD) and generalized screen (GSP) are two of the most general members of the mixed-domain wave-equation migration family. For the same order of approximation, GSP can achieve a higher angular accuracy than FFD, although GSP's implementation is not as straightforward as that of FFD, and its stability is harder to ensure. Other members of the family can be easily obtained by simply neglecting some of the terms in the general equations. This paper serves as a tutorial that brings together all the members of the family in a unified framework.

By analogy with mixed-domain migration operators, I generalize the wave-equation migration velocity analysis operator. Many other approximate formulae can be derived from the general WEMVA equations. The approximations with the largest impact are those based only on the background slowness, which enable linearized image perturbation - slowness perturbation relationship.

Simple backprojection examples illustrate the band-limited character of velocity analysis using the wave-equation. I present WEMVA ``fat'' rays that are easy to correlate to high-frequency trajectories obtained by conventional ray-tracing.