Crustal seismic anisotropy in central Tibet: Implications for deformational style and flow in the crust

Receiver functions obtained at INDEPTH III stations located near the Bangong‐Nujiang suture in central Tibet display a weak Moho signal and strong P to S conversions within the first 5 s that vary systematically with back‐azimuth. A single station with representative azimuthal variations located at the sharp onset of strong SKS splitting, is modeled for both dipping layers and seismic anisotropy by using a global minimization technique. Inversion results indicate strong anisotropy (>10%) near the surface and in the middle crust separated by a south‐dipping (∼25°) layer, possibly related to the earlier phase of crustal shortening. Near‐surface anisotropy has a fabric dipping steeply southward and trending WNW‐ESE that correlates with the suture and younger strike‐slip faults. In contrast, mid‐crustal anisotropy occurs in a low‐velocity zone and has a fabric dipping gently (∼18°) northward that might be related to a well‐developed near‐horizontal rock fabric induced by crustal flow.