Crustal anisotropy beneath the southeastern tibetan plateau and the lateral extension of the plateau

Crustal anisotropy can reveal deformation mechanisms within the crust. In this study, we investigated crustal anisotropy beneath the southeastern Tibetan Plateau using radial and tangential receiver functions from permanent seismic stations. Results show an average delay time of approximately 0.41 s, with NW-oriented fast wave directions (FWD) dominating the Songpan-Ganzi and Northwestern Sichuan Block. The Dianzhong Block exhibits a north-south FWD transition from NNW to NNE. South of 26°N, weak anisotropy (delay time of ~0.2 s) and scattered FWD suggest minimal mid-lower crustal flow. The contrasting anisotropy patterns imply crustal flow driven by plateau extension in the north, whereas the southern region exhibits more complex deformation. These findings provide important constraints for refining models of crustal dynamics along the southeastern margin of the Tibetan Plateau.