Direct arrivals from walkaway vertical seismic profiling or VSP survey data are used to derive Green's functions representing the seismic wave amplitude and travel time information required to extrapolate the vertical seismic profiling survey data from individual wellbore receivers to the individual source locations. The derived Green's functions are employed in a convolution process with upcoming primary wavefields from the VSP survey data for other surface locations. The derived Green's functions are also used in a correlation process with downgoing wavefields from the VSP survey data to extend lateral coverage of the VSP image. The sets of VSP-CMP gathers so formed are then processed to obtain information about the subsurface formations.