Seismic modeling by demigration

Kirchhoff-type, isochron-stack demigration is the natural asymptotic invers e to classical Kirchhoff or diffraction-stack migration. Both stacking oper ations can be performed in true amplitude by an appropriate selection of we ight functions. Isochron-stack demigration is closely related to seismic mo deling with the Kirchhoff integral. The principal objective of this paper i s to show how demigration can be used to compute synthetic seismograms. The idea is to attach to each reflector in the model an appropriately stretche d (i.e., frequency-shifted) spatial wavelet. Its amplitude is proportional to the reflection coefficient, transforming the original reflector model in to an artificially constructed true-amplitude, depth-migrated section. The seismic modeling is then realized by a true-amplitude demigration operation applied to this artificially constructed migrated section. A simple but ty pical synthetic data example indicates that modeling by demigration yields results superior to conventional zero-order ray theory or classical Kirchho ff modeling.