Diffuse Deformation in the SE Tibetan Plateau: New Insights From Geodetic Observations

The southeastern Tibetan Plateau is a key component in the India-Eurasia collision zone, which is characterized by spatially prevalent strike-slip fault systems with devastating earthquakes. However, slip rates on some of these faults are still poorly constrained, hindering an understanding of kinematic and dynamic processes in this region. We analyze contemporary crustal deformation in the SE Tibetan Plateau based on the latest, dense geodetic observations. Slip rates on a set of dextral NW/NNW-striking faults are determined using a 3-D elastic half-space dislocation model. Our results show that boundary faults such as the Red River and Lancangjiang faults yield dextral slip rates ranging from 1 to 3 mm/a, similar to those of other small-scale sub-parallel faults such as the Chuxiong, Qujiang, and Wuliangshan faults. Additionally, sinistral slip of the Xiaojiang fault may have partly transferred to transpressional slip on the Qujiang, Jianshui, and central Red River faults, which increase seismicity on these faults. New seismic relocation results, geodetic measurements, and existing structural observations show the geometry of this dextral fault system at the depth, which may be restricted above or within the rheologically weak mid-lower crust rather than cutting into the mantle. Results confirm that the SE Tibetan Plateau is characterized by on-going diffuse deformation between the Sagaing and Xianshuihe-Xiaojiang faults. Driven by the northward advance of the eastern Himalayan syntaxis and southward crustal extrusion, distributed right-lateral movements occurred along the NW/NNW-striking fault system.