Methods and systems are disclosed to enhance surveying techniques. In one embodiment, a virtual response is estimated that corresponds to energy propagated within a subsurface region between a virtual source and a virtual source estimation receiver, wherein the subsurface region corresponds to a survey zone including: a plurality of receivers deployed within the survey zone, a first subzone having at least one actual source, a second subzone within the first subzone; the virtual source is a first receiver disposed in the second subzone; and the virtual source estimation receiver is a second receiver.