What is DMO coverage?

'Coverage' or 'fold' is defined as the multiplicity of common-midpoint (CMP ) data. For CMP stacking the coverage is consistent with the number of trac es sharing a common reflection point on flat subsurface reflectors. This re lationship is not true for dipping reflectors. The deficiencies of CMP stac king with respect to imaging dipping events have long been overcome by the introduction of the dip-moveout (DMO) correction. However, the concept of c overage has not yet satisfactorily been updated to a 'DMO coverage' consist ent with DMO stacking. A definition of constant-velocity DMO coverage will be proposed here. A subsurface reflector will be illuminated from a given s ource and receiver location if the time difference between the reflector ze ro-offset traveltime and the NMO- and DMO-corrected traveltime of the refle ction event is less than half a dominant wavelength. Due to the fact that a subsurface reflector location is determined by its zero-offset traveltime, its strike and its dip, the DMO coverage also depends on these three param eters. For every surface location, the proposed DMO coverage consists of a 3D fold distribution over reflector strike, dip and zero-offset traveltime.