Where two or more reflections are more closely spaced than a quarter wavelength, a common situation for stratigraphic features of interest in petroleum exploration, the same half-cycles of the embedded wavelet tend to add; we call this the “thin-bed” case. In contrast, where they are close but separated by more than a quarter wavelength, different half-cycles tend to add; this is the “thick-bed” case. Many characteristics of seismic reflections differ in thinand thick-bed situations.
On unmigrated seismic sections the limits of horizontal resolvability are imposed by Fresnel-zone considerations. However, on migrated sections other factors become important, such as noise on the unmigrated section, spatial aliasing, migration aperture, and uncertainties imposed by velocity, stacking, and two-dimensional assumptions.