| This thesis develops a new computation of the objective function and gradient for normal moveout-based differential semblance (DS). The DS principle underlies a class of algorithms for seismic velocity analysis. The simplest variant of DS is based on a drastic approximation to the scattering of waves, called "normal moveout" (NMO) in the seismic literature. This simple NMO-driven DS algorithm is very fast relative to other variants based on more faithful approximations to wave physics, but nonetheless accurate enough to be used to process field data. A recent implementation of NMO-based DS demonstrated these capabilities, but it also exhibited numerical irregularity which may have affected the stability of its velocity estimates. My alternative approach avoids interpolation noise that existed in previous work and so results in more stable numerical optimization. |
