FIG. 2. Prestack depth migration common image point gathers showing residual moveout (RMO) sensitivity to small velocity (Vel.) errors, for a simple one-dimensional model simulating the water table reflection with a 0.12 m/ns vadose zone and 0.07 m/ns water-saturated zone. The RMO is negative when the velocity is too low, and positive when the velocity is too high.