We propose a dual-domain, one-way, elastic thin-slab method for fast and accurate amplitude variation with offset (AVO) modeling. In this method, the wavefield propagates in the wavenumber domain and interacts with heterogeneity in the space domain. The approach requires much less memory and is two to three orders of magnitude faster than a full-wave method using finite difference or finite element.
The thin-bed AVO and AVOs with lateral parameter variations have been conducted using the thin-slab method and compared with reflectivity and finite-difference methods, respectively. It is shown that the thin-slab method can be used to accurately model reflections for most sedimentary rocks that have intermediate parameter perturbations ( for P-wave velocity and for S-wave velocity). The combined effects of overburden structure and the scattering associated with heterogeneities on AVO have been investigated using the thin-slab method. Properties of the target zone and overburden structure control the AVO trends at overall offsets. Scattering associated with heterogeneities increases local variance in the reflected amplitudes and becomes significant for the sedimentary models with weak reflections. Interpretation of AVO observations based on homogeneous elastic models would therefore bias the estimated properties of the target. Furthermore, these effects can produce different apparent AVO trends in different offset ranges.