PS-wave AVAz and challenges for joint inversion

Changes in fracture direction across interfaces can have an important impact on PS-wave reflection coefficients in azimuthally anisotropic media. Extending conventional joint inversion with P-waves to include amplitude variations with azimuth (AVAz) would use radial and transverse reflection coefficients (RPSV and RPSH, respectively), and present a number of challenges. One of these is that layerstripping (LS) must be done either prior to or during joint inversion with fast PS1- and slow PS2-waves for azimuthal rock properties (e.g., fractures or stress directions). Also, null amplitude directions of RPSH can be shifted in azimuth when fracture direction changes across the interface, and will be different from the actual fracture direction. Thus, a full waveform inversion (FWI) approach with-out registering PS-waves to P-wave time could be more practical than attempting to align them prior to joint AVAz inversion.