We introduce a methodology for locally fitting the apparent background trend of AVO Intercept and Gradient data (A and B), using a 3D seismic dataset from offshore Australia. We use Shuey’s two-term approximation to generate A and B from the near and far depth angle stacks. The A and B data are parsed into patches, and the background trend is estimated for each patch using a weighted mean angle algorithm in polar coordinates space. The resultant spatially varying angles (SVA) volume of the approximated trends can be used directly for interpretation, or as an input to the Extended Elastic Impedance (EEI) formula to rotate the A and B coordinates and produce a spatially varying Chi (SVC) volume.
Results suggest the SVA and SVC volumes can be used to understand local variations in seismic images and therefore lithology, as well as highlight off-trend (anomalous) data or dim on-trend data. Potential remains for applications of this method as a property estimation tool, but additional work is required.
