Apparatus, computer instructions and method for processing seismic data related to a subsurface of a body of water. The method includes inputting data indicative of recordings made by detectors disposed on a depth-changing profile in response to an acoustic wave reflected from the subsurface; applying a matched mirror migration procedure to the data, wherein the matched mirror migration procedure uses an up-traveling U wave and a down-traveling D wave, at least one of the up-traveling U wave or the down-traveling D wave being constructed based on (i) actual positions of the detectors disposed on the depth-changing profile and corresponding recordings, and (ii) fictitious mirror positions of the actual detectors on the depth-changing profile and corresponding recordings with a changed sign; and generating in a processor an image of the subsurface based on the matched mirror migration procedure.