Lowrank RTM for converted wave imaging

This paper is an attempt to fill the technology gap existing between pure P- and PS-wave imaging. Full wavefield extrapolation techniques are well developed for P-wave and RTM has been now available for almost a decade. Conversely, ray based migration algorithms are still the workhorse for converted-wave (PS-wave) depth imaging. Here, we introduce a new converted-wave anisotropic RTM, using a low-rank decomposition of mixed-domain space-wavenumber propagators for quasi-P and quasi-S waves. These operators are formal integral solutions of the pure-mode wave equations which guarantee stable and dispersion-free time extrapolation for coarse time steps in anisotropic, heterogeneous media. The puremode extrapolators are attractive for both PS-wave structural imaging and velocity analysis. An ocean bottom cable synthetic example illustrates the effectiveness of low-rank PS-wave RTM when compared against state-of-the-art Gaussian beam and finite difference RTM algorithms.