DSR one-way wave equation prestack τ migration

By transforming the classical double-square-root(DSR) one-way wave equation from the depth domain to the two-way vertical traveltime(τ) domain,we derive an one-way DSR wave propagator which can be applied to mathematically implement sinking survey.Its algorithm to recursively continue the source and receiver wavefields,which includes a wavenumber domain phase shift in a constant background medium followed by a phase correction in the space domain that accommodates lateral velocity variations,can tackle the effects of lateral velocity variations for imaging under complex overburdens.Combing with the zero-offset and zero-time imaging condition,we develop a DSR equation prestack migration method that implements wavefield continuation and imaging in the τ space.To address the problems that full volume 3-D DSR equation migration could meet with in production application,we present a feasible common-azimuth prestack τ migration approach based on the theory of crossline common-offset migration.Numerical tests show that DSR equation prestack τ migration provides a significant improvement over the traditional prestack time migration technology in laterally varying media.