The nonlinearity of the seismic amplitude-variation-with-offset (AVO) response in the presence of large relative changes in acoustic and elastic medium properties is investigated with physical modelling data. A procedure for pre-processing reﬂection data, acquired using the CREWES-University of Calgary physical modelling facility, is enacted on a reﬂection from a water/plexiglas boundary. The resulting picked and processed amplitudes are compared with exact solutions of the plane-wave Zoeppritz equations, as well as ﬁrst, second, and third order RPP approximations. We conclude that in the angle range 0 − 20◦ , the third order approximation is sufﬁcient to capture the nonlinearity of the AVO response to within roughly 1% from a liquid-solid boundary with VP , VS and ρ contrasts of 1485 − 2745m/s, 0 − 1380m/s, and 1.00 − 1.19gm/cc respectively. This is in contrast to the linear Aki-Richards approximation, which is in error by as much as 25% in the same angle range.
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