We propose to perform a systematic study of azimuthal anisotropy from shearwave splitting of the body-wave phase SKS. We will estimate the azimuth of the fast direction and the differential travel time between the fast and slow components for all of the available digital stations. this will provide a global map of the radically averaged azimuthal anisotropy of the mantle. In a preliminary study, we have successfully developed a simple and robust measuring technique yielding estimates for each SKS recording. Anisotropy is clearly seen for several stations with values as large as 2 seconds. Since anisotropy most probably results from the preferred orientation of mantle crystals, it may be used to study stresses associated with mantle flow as well as present-day continental and oceanic tectonics. In addition, our preliminary results suggest that in at least one case, the anisotropy may reflect a fossil Archean stress field associated with shield formation. This raises the intriguing possibility that anisotropy may additionally be used to study continental evolution. For this reason, we will utilize tectonic, structural geology, and crustal stress information, to determine if the observed anisotropy can be associated with present day tectonics or with tectonic episodes in the past.
