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Abstract:
The Sanjiang lateral collision zone in the SE margin of the Tibetan plateau is a crucial area for the study of the collision between the Paleotethys orogenic belt and the oblique subduction of the Neotethys. In this study, we used data from three temporary seismic arrays and regional permanent stations to obtain shear wave velocity and azimuthal anisotropy for depths of 3 km to 50 km. Our results suggest that geometry of the low velocity zone along the Lijiang-Xiaojinhe fault (LXF), the fast velocity directions (FD) parallel to the LXF, and the nearly E-W oriented FDs in the Panzhihua region with high-velocity may indicate that the high-velocity blocks obstruct the southeastward migration of the Tibetan Plateau materials. The FDs at the northwestern end of the Red River fault (RRF) exhibit obvious segmented characteristics. This anisotropic pattern may reflect both the decoupling deformation of the upper and lower crust in the north and the coupling deformation in the south, as well as the strong influence of the RRF on anisotropy. The clockwise rotation of the crustal anisotropy in the western part of the study area may suggest that the deformation is related to the complicated geological tectonic and extensional cracks. The microcracks associated with regional compression may be responsible for the N-S trending crustal anisotropy in the east. In addition, the complex anisotropy in the LXF and RRF also highlights the important role of these faults in shaping crustal deformation [supported by NSFC Project 41730212].
