f Pre-stack turning ray imaging with a 60° operator

Seismic energy traveling in an inhomogeneous medium may move along a curving ray path causing wavefronts which were originally going downward to turn through 90 degrees and move back toward the surface. Special algorithms are required to image reflectors which are illuminated by turning rays if the imaging is done poststack, since the only path between the surface and the reflector seen by the migration is a turning ray path.