Multiple Weights in Diffraction Stack Migration

A primary offset reflection of a point source from a smooth reflector within a laterally inhomogeneous velocity earth model is (within the framework ofray theory) defined by parameters pertaining to the reflected ray. Important seismic quantities of the primary reflection ray can be recovered from traveltime measurements on the surface. Among these quantities are the geometrical-spreading factor of the ray at the receiver, the incidence and emergence angles of the ray with the surface normal, the angle between the incidence and reflection ray and the reflector dip a.t the reflection point. The above quantities can be obtained by weighted Kirchhoff diffraction stacks using different weight functions. The diffraction stack and the weight functions are computed using a given macro-velocity model. The use of multiple weights in the diffraction stack can be thought of as a vector diffraction stack in which the weight function is a vector with two or more component functions. In this way, amplitude-preserving migration schemes may be applied more efficiently.