Double-square-root one-way wave equation prestack tau migration in heterogeneous media

In this paper, source-receiver migration based on the double-square-root one-way wave equation is modified to operate in the two-way vertical traveltime (tau) domain. This tau migration method includes reasonable treatment for media with lateral inhomogeneity. It is implemented by recursive wavefield extrapolation with a frequency-wavenumber domain phase shift in a constant background medium, followed by a phase correction in the frequency-space domain, which accommodates moderate lateral velocity variations. More advanced tau-domain double-square-root wave propagators have been conceptually discussed in this paper for migration in media with stronger lateral velocity variations. To address the problems that the full 3D double-square-root equation prestack tau migration could meet in practical applications, we present a method for downward continuing common-azimuth data, which is based on a stationary-phase approximation of the full 3D migration operator in the theoretical frame of prestack tau migration of cross-line constant offset data. Migrations of synthetic data sets show that our tau migration approach has good performance in strong contrast media. The real data example demonstrates that common-azimuth prestack tau migration has improved the delineation of the geological structures and stratigraphic configurations in a complex fault area. Prestack tau migration has some inherent robust characteristics usually associated with prestack time migration. It follows a velocity-independent anti-aliasing criterion that generally leads to reduction of the computation cost for typical vertical velocity variations. Moreover, this tau-domain source-receiver migration method has features that could be of help to speed up the convergence of the velocity estimation.