Plane-wave migration in tilted coordinates

Abstract:

Most existing one-way wave-equation migration algorithms have difficulty in imaging steep dips in a medium with strong lateral velocity variation. We propose a new one-way wave-equation-based migration, called ``plane-wave migration in tilted coordinates.'' The surface data are converted to plane-wave source data by slant-stacking processing, and each resulting plane-wave source dataset is migrated independently in a tilted coordinate system with an extrapolation direction determined by the source plane-wave direction at the surface. For most waves illuminating steeply dipping reflectors, the extrapolation direction is closer to their propagation direction in the tilted coordinates. Therefore, plane-wave migration in tilted coordinates can correctly image steeply dipping reflectors, even by applying one-way extrapolators. In a well-chosen tilted coordinate system, waves that overturn in conventional vertical Cartesian coordinates do not overturn in the new coordinate system. Using plane-wave migration in tilted coordinates, we can image overturned energy with much lower cost compared to reverse-time migration.

Plane-wave migration in tilted coordinates