Azimuthally Anisotropic Effective Parameters from Full-azimuth Reflection Angle Gathers

We present an efficient and stable procedure for estimating second- and fourth-order azimuthally-dependent effective parameters from full-azimuth residual moveouts. The residual moveouts are automatically picked at depth image points along full-azimuth angle domain reflection angle gathers. It is assumed that the azimuthally varying residual moveouts are due to fracture systems within compacted sand/shale sediment layers which were not accounted for in the seismic migration. The extracted (up to eight) effective parameters can then be used to obtain local (layer) effective parameters, characterizing the intensity and orientation of the fracture systems at each layer. Finally, the local effective parameters can be inverted to obtain interval anisotropic (e.g., orthorhombic) model parameters to be used in orthorhombic seismic migration.