Two assumptions are made here: first, rays traveling through the subsurface are confined to the vertical plane that contains the sources and receivers (a 2-D assumption). Second, no lateral velocity variation exists in the region of the analysis (a time-processing assumption). However, some treatment to lateral inhomogeneity is applied in the NMO correction stage. Violating the first assumption will degrade the anisotropic processing result and generally reduce the degree of anisotropy measured. Therefore, measurements from out-of-plane reflections will not be mistaken for anisotropy (Lynn et. al., 1991). If anything, measurements from out-of-plane reflections will lower the value of due to the lower NMO velocities associated with out-of-plane reflections. Violating the second assumption will result in errors similar to those encountered using isotropic time processing in areas of lateral inhomogeneity. These errors are dependent on the degree of lateral inhomogeneity, and as is likely here, such errors are expected to be small.