Performance bounds on shear anisotropy azimuth estimation using borehole sonic logging tools

The problem of estimating the azimuths of the principal axes of anisotropy as measured by an array of dipole sensors on a borehole sonic tool is addressed from the perspective of performance. While algorithms for estimating the azimuth have been proposed and deployed in the field, their performance has not been hitherto studied with respect to theoretical bounds. We compute the performance bounds for the azimuth estimation problem for a number of assumed models and compare its performance to that of published algorithms.