Thin‐bed AVO: Compensating for the effects of NMO on reflectivity sequences

Abstract

Estimating the amplitude versus offset (AVO) gradient for thin beds is problematic because of offset‐dependent tuning and NMO stretch. When AVO analysis is carried out before NMO correction, the nonparallel nature of the NMO hyperbolas results in differential interference conditions at each offset and complicates AVO interpretation. If AVO analysis is carried out after NMO correction, the data bandwidth is distorted and corrections must be made to recover the true AVO response. A correction for NMO stretch can be applied to Fourier spectra obtained after windowing the NMO‐corrected prestack data. This approach requires knowledge of the seismic wavelet but seems to be relatively insensitive to noise in the data or uncertainties in the wavelet estimation. The technique allows the interference conditions to be made independent of offset and the correct AVO gradient relative to the normal incidence amplitude to be recovered.