DMO

DMO is much cheaper than full prestack migration because the spatial aperture of the DMO operator in constant offset sections is limited by the offset, while the corresponding full prestack migration operator has unlimited width. The gain in efficiency is important in a 2-D medium, but it is dramatic in a 3-D medium.

DMO is usually applied as a velocity independent processing. A velocity independent DMO is correct when the velocity is constant; it is approximately correct when the velocity varies with depth, but it produces wrong the results in the presence of strong lateral velocity variations. In these cases the standard processing of NMO followed by DMO cannot be used because the moveouts in common midpoint gathers are not any more hyperbolic, but the focusing can still be accomplished in the single step procedure which is the prestack partial migration (Yilmaz and Claerbout, 1980).