Velocity continuation and the anatomy of residual prestack time migration

摘要

Velocity continuation is an imaginary continuous process of seismic image transformation in the postmigra-tion domain. It generalizes the concepts of residual and cascaded migrations. Understanding the laws of velocity continuation is crucially important for a successful application of time-migration velocity analysis. These laws predict the changes in the geometry and intensity of reflection events on migrated images with the change of the migration velocity. In this paper, I derive kinematic and dynamic laws for the case of prestack residual migration from simple geometric principles. The main theoretical result is a decomposition of prestack velocity continuation into three different components corresponding to residual normal moveout, residual dip moveout, and residual zero-off set migration. I analyze the contribution and properties of each of the three components separately. This theory forms the basis for constructing efficient finite-difference and spectral algorithms for time-migration velocity analysis.