Phase variation with angle inversion using plane and spherical waves

Abstract

Seismic reflection data from near-to post-critical angles provide the potential of both velocity and density inversion. It is known that plane wave solutions are inapplicable near the critical angle. Spherical-wave solutions have recently been considered to study the amplitude variation with offset (AVO). However, amplitude is difficult to extract reliably due to transmission losses. To overcome this, we propose to use the phase variation with angle (PVA) information for elastic parameter inversion. The modeling is by spherical-wave reflection coefficients (SRCs). A linearized least-squares scheme is used to invert the modeled PVA for density and three velocities across the reflector. Numerical tests indicate that a correct solution can be reached only when the models are consistent for both observed and predicted phases. A spherical-wave model can produce a more accurate solution for real (spherical-wave) data than a plane-wave model can.