Nguyen, B. and McMechan, G.A., 2009. Options for source wavefield reconstruction in prestack reverse-time migration. Journal of Seismic Exploration, 18: 305-314. One of the main steps in prestack reverse-time migration is recovery of the source wavefield at each time step during the reverse-time extrapolation of the receiver wavefield. This recovery can be accomplished in a number of ways, each of which has it’s advantages, disadvantages, and computational and data storage requirements. Two types of source wavefield recovery exist. The most common (and the most expensive) approach to source wavefield recovery is computing and saving the wavefield snapshots and accessing them in reverse-time order; the most economical approaches involve reconstruction of the source wavefield, at each time step, from boundary or initial conditions (or a combination of these). The advantages of reconstruction are most obvious in 3D, where the disk storage requirement is reduced by at least two orders of magnitude compared to saving all the time snapshots.