INVERSION VERSUS MIGRATION - A NEW PERSPECTIVE TO AN OLD DISCUSSION

Seismic imaging techniques can be subdivided into inversion and migrat ion. The object functions for inversion and migration are, respectivel y, the medium contrast parameters and reflectivity. In this paper, the relationship between inversion and migration is approached by analyzi ng the underlying representations (the forward models). It appears tha t the ''two-way representation'' (which underlies inversion) as well a s the ''one-way representation'' (which underlies migration) can both be expressed in terms of a volume integral over the appropriate object function. In their linearized form, these representations account for primaries only. In this case, the one-way representation in terms of reflectivity is the most accurate of the two, which implies that prope r migration is more accurate than linearized inversion. Internal multi ples can be taken into account by the nonlinear representations. As an alternative, however, the ''generalized primary representation'' is i ntroduced. In its explicit form, this one-way representation is linear in the reflectivity (opposed to linearized). Nonlinear effects are im plicitly accounted for by the generalized primary propagators. The gen eralized primary representation is a suitable basis for true amplitude migration, taking the angle-dependent dispersive effects of fine laye ring into account.