2.5-D true-amplitude Kirchhoff migration to zero offset in laterally inhomogeneous media

Abstract

The proposed new Kirchhoff-type true-amplitude migration to zero offset (MZO) for 2.5-D common-offset reflections in 2-D laterally inhomogeneous layered isotropic earth models does not depend on the reflector curvature. It provides a transformation of a common-offset seismic section to a simulated zero-offset section in which both the kinematic and main dynamic effects are accounted for correctly The process transforms primary common-offset reflections from arbitrary curved interfaces into their corresponding zero-offset reflections automatically replacing the geometrical-spreading factor. In analogy to a weighted Kirchhoff migration scheme, the stacking curve and weight function can be computed by dynamic ray tracing in the macro-velocity model that is supposed to be available. In addition, we show that an MZO stretches the seismic source pulse by the cosine of the reflection angle of the original offset reflections. The proposed approach quantitatively extends the previous MZO or dip moveout (DMO) schemes to the 2.5-D situation.