1. A computer-implemented method for target-oriented reverse time migration for prestack depth imaging, the method including: acquiring prestack seismic data for a subsurface region; determining, via a computer, an earth model for the subsurface region; determining, via a computer, an acquisition area within the earth model; determining, via a computer, a reference surface near a target within the earth model; exciting, via a computer, wavefields from the reference surface; propagating, via a computer, the excited wavefields through the earth model; recording, via a computer, the wavefields at receiver locations in the acquisition area and at the target; synthesizing, via a computer, wavefields along the reference surface to reconstruct Green's functions which relate the receiver locations in the acquisition area to the target; and utilizing, via a computer, the Green's functions and prestack seismic data to determine subsurface characteristics of the subsurface region.