Seismic traces synthesizing the response of subsurface formations to a cylindrical or plane wave are obtained for a succession of shotpoint locations along a seismic line of profile. The traces obtained are then wavefront steered and the steered traces and original trace for each shotpoint are summed. Groups of these traces for a line of profile are assembled to form a steered section. A number of these sections are then individually imaged or migrated, and the migrated sections are summed to form a migrated two-dimensional stack of data from cylindrical or plane wave exploration. Reflectors may then be located by finding common tangents.The traces for those shotpoints of the several lines which lie in planes perpendicular to the lines are then assembled and processed in the foregoing manner to obtain three dimension migrated seismic data.