f Accurate migration using offset-checkshot surveys

Accurate seismic migration, particularly of steeply dipping or overturned reflectors, requires an accurate velocity model (Lamer, Beasley et al . 1989). Recent research has focused on the notion that the migration velocity model must include velocity anisotropy (Alkhalifah and Lamer 1994; Larner and Cohen 1993; Lynn, Gonzalez et al. 1991). While it is true that most migration algorithms require accurate velocity models, Kirchhoff migration is an exception to this rule. Unlike most migration methods, Kirchhoff migration does not require a velocity model as input. Rather, all that is required is a table listing the seismic traveltime from subsurface imaging points to points in the surface migration aperture (Gray and May 1994). Thus, in the case of Kirchhoff migration, accurate traveltime tables would ensure a kinematically accurate image.