A method of characterizing shear wave anisotropy in a formation includes
obtaining crossed-dipole waveforms from a borehole penetrating the
formation over a range of depths and frequencies, determining far-field
slowness in a fast-shear and slow-shear direction using a low-frequency
portion of the crossed-dipole waveforms, and determining near-wellbore
slowness in the fast-shear and slow-shear directions using a
high-frequency portion of the crossed-dipole waveforms. The method also
includes marking a selected depth of the formation as having intrinsic
anisotropy if at the selected depth the far-field slowness in the
fast-shear direction is less than the far-field slowness in the
slow-shear direction and the near-wellbore slowness in the fast-shear
direction is less than the near-wellbore slowness in the slow-shear
direction. The selected depth is marked as having stress-induced
anisotropy if the far-field slowness in the fast-shear direction is less
than the far-field slowness in the slow-shear direction and the
near-wellbore slowness in the fast-shear direction is greater than the
near-wellbore slowness in the slow-shear direction.