Residual moveout in angle gathers for converted waves

Abstract

Multicomponent seismic data have been increasingly collected, for example, with ocean-bottom node/cable surveys. Although the converted waves recorded in multicomponent seismic data have the potential to better illuminate the areas underneath complex structures than P-waves, they have not been widely used in depth imaging. Common industry practice is still limited to P-waves only mainly because the successful imaging of converted waves in prestack depth migration relies on accurate velocity models for P- and S-waves. However, the S-wave velocity model estimation via analysis of converted-wave moveout and tomography is still immature. We derive a general residual moveout (RMO) relation as a function of incident angle or as a reflection angle for converted waves, which can be used for converted-wave tomography based on angle-domain common-image gathers. Our derivation does not have certain limitations, such as slowly changing reflection angles or constant P/S-wave velocity ratios, as in existing algorithms available in the literature. Therefore, the proposed RMO equations are more accurate and can be helpful for S-wave velocity model building. The derived equations are validated using different numerical tests.