Post-Critical and Near-Critical Reflections in Seismic Avo Inversion

Abstract

Summary In this paper the role of near-critical and post-critical angles in AVO inversion is investigated. Three different methods for forward modelling of near/post critical angle AVO data are presented: the Kennett method, the differential elastic wave-equation and the integral representation of the elastic wave-equation. For inversion of near and post critical data only the integral representation of the elastic wave-equation is used. A comparison is made, first between conventional AVO inversion and wave-equation based inversion for angles well below critical angle, and subsequently between wave-equation based inversion for the low angle range, and for a high angle range where for some layers critical angle is exceeded. It turns out that the biggest improvement is between conventional inversion and wave-equation based inversion for the low angle data. There is little improvement between the results of wave-equation based inversion for the relatively low angle data, and the results of wave-equation based inversion for the high angle data for which in places critical angle is exceeded. This is explained by qualitative analysis of the information content of high angle illumination data.