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 an earth model for the subsurface region; determining an acquisition area within the earth model and determining a reference surface near a target within the earth model; exciting wavefields from the reference surface and propagating the excited wavefields through the earth model; recording the wavefields at receiver locations in the acquisition area and at the target; synthesizing wavefields along the reference surface to reconstruct Green's functions which relate the receiver locations in the acquisition area to the target; and utilizing the Green's functions and prestack seismic data to determine subsurface characteristics of the subsurface region.