Obtaining AVO and AVA curves from CRS attributes

We present a method to obtain amplitude-versus-o set (AVO) and amplitude-versus-angle (AVA) curves at selected depth points using the three attributes generated by the Common Re Surface (CRS) stack, the emergence angle and the two hypotetical wavefront curvatures associated to each zero-o set ray simulated. Our approach combines the CRS stack/inversion process applied to multicoverage data and the use of a kinematic Kirchho migration to achieve true-amplitudes (TA) at assigned depth points in the migrated images. The proposed method consists of the following steps: apply the CRS process to the given multicoverage data; the obtained CRS attributes are then used to produce a simple macro-velocity depth model; perform an unweighted Kirchho migration for imaging purposes only; for selected points on target re in the migrated image, we use ray tracing within the macro-velocity model to determine, by ray tracing, common-re (CRP) gathers that belong to the input data; for these rays, we compute the incident angles and the geometrical spreadings; go back to CRP gathers and compensate the amplitudes for geometrical spreading. The whole process permits to construct AVA curves on the assigned CRP's. In summary, our method is designed to aggregate amplitude information on selected points of a re after a purely kinematic image (migration) has been obtained. The method is tested on a synthetic inhomogeneous layered model with encouraging results.