Designing Explicit Wavefield Extrapolators For Depth Migration and Migration Velocity Analysis
Saleh M. Al-Saleh
Recursive explicit wavefield extrapolation methods are a powerful tool for imaging complex geological subsurface structures. These methods, however, have three major problems: (1) they require short, stable operators to be computationally efficient, (2) they assume that extrapolation proceeds from a flat surface, and (3) they are very sensitive to velocity models. In this thesis, some improvements to existing methods are proposed, and new algorithms are developed where appropriate.
A new technique for designing practically stable wavefield extrapolators is shown. This approach is then used to optimize the forward operator and conjugate inverse (FOCI) algorithm. Downward-continuation can be efficiently implemented directly from topography by building wavefield extrapolators that can handle lateral velocity and topography variations.
Three domains for migration velocity analysis (MVA) are derived in the same context and reformulated as mathematical hypotheses. Different aspects of these domains are combined into a unified domain that offers more prestack information than the three individual domains.