2.5-D TRUE-AMPLITUDE KIRCHHOFF MIGRATION TO ZERO OFFSET IN LATERALLY INHOMOGENEOUS-MEDIA

The proposed new Kirchhoff-type true-amplitude migration to zero offse t (MZO) for 2.5-D common-offset reflections in 2-D laterally inhomogen eous layered isotropic earth models does not depend on the reflector c urvature. It provides a transformation of a common-offset seismic sect ion to a simulated zero-offset section in which both the kinematic and main dynamic effects are accounted for correctly The process transfor ms primary common-offset reflections from arbitrary curved interfaces into their corresponding zero-offset reflections automatically replaci ng the geometrical-spreading factor. In analogy to a weighted Kirchhof f migration scheme, the stacking curve and weight function can be comp uted by dynamic ray tracing in the macro-velocity model that is suppos ed to be available. In addition, we show that an MZO stretches the sei smic source pulse by the cosine of the reflection angle of the origina l offset reflections. The proposed approach quantitatively extends the previous MZO or dip moveout (DMO) schemes to the 2.5-D situation.