AVO and elastic impedance

A mplitude-variation-with-offset (AVO) has been used extensively in hydrocarbon exploration over the past two decades. Traditional AVO analysis involves computation of the AVO intercept and gradient from a linear fit of P-wave reflection amplitude to the sine square of the angle-of-incidence. This linear fit is based on the approximate P-wave reflection coefficient formulation in intercept-gradient form, given by Bortfeld (1961) and Shuey (1985) among others. Under the assumption of a background P-S velocity ratio of two, the AVO intercept and gradient values can also be combined to obtain additional AVO attributes such as pseudo S-wave data and Poisson's ratio contrast. AVO intercept and pseudo S-wave data are also used in conjunction with prestack waveform inversion by Mallick et al. (2000) in a hybrid inversion scheme.