Linear-transform techniques for processing shear-wave anisotropy in four-component seismic data

Most published techniques for analyzing shear-wave splitting tend to be computing intensive, and make assumptions, such as the orthogonality of the two split shear waves, which are not necessarily correct. We present a fast linear-transform technique for analyzing shear-wave splitting in four-component (two sources/ two receivers) seismic data, which is flexible and widely applicable.We transform the four-component data by simple linear transforms so that the complicated shear-wave motion is linearized in a wide variety of circumstances. This allows various attributes to be measured,including the polarizations of faster split shear waves and the time delays between faster and slower split shear waves, as well as allowing the time series of the faster and slower split shear waves to be separated deterministically. In addition, with minimal assumptions, the geophone orientations can be estimated for zero-offset verticle seismic profiles (VSPs), and the polarizations of the slower split shear waves can be measured for offset VSPs. The time series of the split shear-waves can be separated before stack for reflection surveys. The technique has been successfully applied to a number of field VSPs and reflection data sets. Applications to a zero-offset VSP, an offset VSP, and a reflection data set will be presented to illustrate the technique.