We have examined shear-wave splitting in teleseismic waves (SKS) recorded on 20 seismographs deployed on aprofile that followed the Southern Tibet highway during the 1992 Sino-French seismic experiment. The crosscorr...We have examined shear-wave splitting in teleseismic waves (SKS) recorded on 20 seismographs deployed on aprofile that followed the Southern Tibet highway during the 1992 Sino-French seismic experiment. The crosscorrelation' method is applied to derive splitting parameters. The most striking feature is the abrupt variation in splitting orientation across ITS. North of ITS, 12 stations have an average N70°'E orientation of the fast wave,with a delay betwee fast and slow waves of up to 1 second. On the contrary, 7 stations located to the southof ITS show an N25°W orientation and a smaller magnitude. We compare the observations with surface geolwical features and discis the source of anisotropy and its constraints on the deformation model of the Tibetan Plateau. Our studies suggest that the anisotropy may be generated by the high strain induced by the underthrusting of the india lithosphere in the south of ITS. North of ITS, anisotropy may relate to ductile deformation and flow in the upper mantle. Analysis of the anisotropy pattern with the deformation models of the Tibetan Plateau suggests that both internal ductile deformation and continental northeastward extrusion contribute to crustal shortening and uplift of the Tibetan Plateau.展开更多
文摘We have examined shear-wave splitting in teleseismic waves (SKS) recorded on 20 seismographs deployed on aprofile that followed the Southern Tibet highway during the 1992 Sino-French seismic experiment. The crosscorrelation' method is applied to derive splitting parameters. The most striking feature is the abrupt variation in splitting orientation across ITS. North of ITS, 12 stations have an average N70°'E orientation of the fast wave,with a delay betwee fast and slow waves of up to 1 second. On the contrary, 7 stations located to the southof ITS show an N25°W orientation and a smaller magnitude. We compare the observations with surface geolwical features and discis the source of anisotropy and its constraints on the deformation model of the Tibetan Plateau. Our studies suggest that the anisotropy may be generated by the high strain induced by the underthrusting of the india lithosphere in the south of ITS. North of ITS, anisotropy may relate to ductile deformation and flow in the upper mantle. Analysis of the anisotropy pattern with the deformation models of the Tibetan Plateau suggests that both internal ductile deformation and continental northeastward extrusion contribute to crustal shortening and uplift of the Tibetan Plateau.
