Azimuthal AVO analysis is typically performed using linearizations of the exact formula for anisotropic reflection coefficients. These approximations often make simplifying assumptions about the types of media on each side of an interface and fail at large angles, especially when there is a large contrast in elastic parameters across the interface. Since the larger angles of incidence are more sensitive to azimuthal anisotropy, this failure can cause poor estimates of azimuthal anisotropy. In order to better understand and reduce the nonlinearity that can adversely affect inversions using linearizations, we analyze higher-order terms of the reflection coefficients. We show that the nonlinearity for large contrasts and long offsets is significant, indicating the need to use exact reflection coefficients in many situations.
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