Present-Day Kinematics in Southeastern Tibet Inferred From GPS Measurements

摘要

Quantifying the regional kinematics is critical for understanding the deformation mechanisms of the Tibetan Plateau. In this study, we construct an elastic block model using a dense GPS velocity field to derive the fault slip rates in SE Tibet. We uncover good agreement between GPS and late Quaternary slip estimates, suggesting that the GPS slip rates estimated from our model can represent the long-term fault motions in SE Tibet. Specifically, our model shows that the slip along the Xianshuihe fault increases from west to east, which may result from the initiation of the Longriba fault. The Litang, Zhongdian, and Xiaojiang faults and the faults bounding the Lijiang block exhibit extensional motions, in agreement with the regional tectonics and earthquake focal mechanisms. In the regions north of the Red River fault whose kinematics can be described through the rotations of subblocks with small residuals, the fault motions agree with focal mechanism patterns and tectonic block models. In regions south of the Red River fault, the right-lateral shearing among the Red River, Lancang and Sagaing faults appears to explain the first-order deformation features. However, the relatively large residuals and complex tectonic setting suggest that various other factors, such as asthenospheric flow and the subduction of the Burma plate may also influence the deformation. Thus, a single model extended to interpret all the geodynamic features in SE Tibet, especially south of the Red River fault, may be overly simple, and the extent to which each factor contributes to this deformation requires further study.