Thin-Bed Spectral Inversion using Prestack Data

In this work we introduce a new method to fully determine the elastic parameters of a thin-bed using prestack seismic data. These parameters include thickness, P- and S-wave velocities, and density. We obtain the exact solution for the AVA response of a thin-bed considering converted P-waves, S-waves and all the associated multiples. We carry out the estimation of the thin-bed parameters in the amplitude spectrum domain using simulated annealing. Contrarily to using zero-offset data, we show that the use of AVA data (PP data only) contributes to increase the robustness of this inverse problem under noisy conditions as well as to significantly reduce its inherent non-uniqueness. To further reduce the nonuniqueness, simulated annealing allows us to easily impose appropriate bounding constraints to the parameters of the upper and lower media, which need not to be known accurately. We illustrate the method by inverting noisy synthetical gathers corresponding to simple wedge models. In addition, we stochastically estimate the uncertainty of the solutions by running simulated annealing several times. The results show that a thin-bed can be fully determined with a high degree of confidence far below the tuning thickness.