Azimuthal variation in the PP seismic signature: Display of high-dimensional data, AVOA modelling and interpretation

Abstract

3D PP full-azimuth, full-offset surveys are being processed to determine the azimuthal variation in AVO (AVOA) and in velocities, among other quantities. A map display of the 3-dimensional number that quantifies the AVOA ? the large AVO gradient, azimuth of the large AVO gradient, and azimuthal variation in the AVO gradient ? tells the viewer about the contrasts in the shear wave birefringence across the boundary. The shear-wave birefringence is usually taken as proportional to the fracture density. Two types of additional information are needed to assess what the P-wave AVOA is telling us: 1) the azimuthal interval velocity information above and below the reflector; and 2) anisotropic AVOA modeling to depict various geologic scenarios likely present at given locations.