Extraction of elastic parameters using seismic reflection amplitude with offset variation

The extraction of elastic parameters from seismic reflection data with the state-of-the-art indicates little success. The specific method tried was the inversion of the seismic reflection amplitude curve with respect to offset angle to yield the elastic parameters on either side of a plane reflection boundary. By numerically evaluating the partial derivatives of the reflection coefficient equation with respect to the elastic parameters, almost all the problems found could be explained. In fact, many of the conclusions by earlier investigators of the reflection coefficient curve such as Koefoed (1955) can also be easily explained by the partial derivatives. The inversion of the reflection coefficient curve for P-waves, when the acoustic impedance ratio is known, is not unique for incidence angles below the critical. This is because the two Poisson's ratios approximately cancel each other's effect on the reflection coefficient. However, when reflection amplitudes above and below the critical angle arS inverted, then a unique solution of the problem is possible, but is highly sensitive to error. Once again, the acoustic impedance ratio is known. For SH-waves, the inversion of the reflection coefficient curve was unique, for the cases studied. A SH-error analysis indicates the inversion is more stable when the acoustic impedance ratio is known. Among the different propagation factors affecting the amplitude curve, and consequently the inversion problem, the most important factor is usually the geophone array.Earth and Atmospheric Sciences, Department o