Elastic parameter estimation

Given depth images of $R_{pp}(\theta)$ from the migration, an inversion for relative changes in elastic parameters can be attempted. This can be achieved in a manner analogous to the AVO procedure of fitting two or three parameters to $R_{pp}(\theta)$ under the linearized Bortfeld approximation to the Zoeppritz relations. I am investigating interesting problems related to the issues of parameter choice, inversion stability, and inversion ``confidence'' quantification. So far, given industry standard surface acquisition geometries, it appears that P and S impedances are the most robust parameters to invert for, and that reflection data contain little or no unambiguous information on density variations for specular coverages less than about 30$^{\circ}$ ($\theta=0^{\circ}$ is defined as normal incidence).