Mingkun Bai

and 10 more

Marie-Luce Chevalier

and 10 more

The Xianshuihe fault in eastern Tibet is one of the most active faults in China, with the next large earthquake most likely to occur along its SE part near Kangding. Quantifying its slip rate along the three parallel branches (Yalahe, Selaha and Zheduotang) as well as along the Moxi fault is essential to evaluate regional earthquake hazard, necessary to the construction of the Chengdu-Lhasa railroad. Here, we expand our previous work on the Selaha fault to the Zheduotang and Moxi faults, with observations on the Yalahe fault and the newly discovered Mugecuo South fault zone. Using tectonic-geomorphology approaches (LiDAR, UAV and 10Be dating), we had determined late Quaternary slip rates of 9.75±0.15 and 4.4±0.5 mm/yr along the NW and SE Selaha fault, respectively, hence had inferred a ~5 mm/yr rate along the parallel Zheduotang fault. Here, using the same methods, we confirm such rate (4.5[+0.9/-0.8] mm/yr, ZDT moraine site) thus suggest a total slip rate of >8.9±1.4 mm/yr in the SE Xianshuihe fault. Our rate along the Moxi fault (12.5[+2.3/-2.1] mm/yr, MX moraine site) is higher than those along the Ganzi (6-8 mm/yr) and Xianshuihe (~10 mm/yr) faults farther NW, which reinforces our earlier finding of a southeastward slip rate increase, in agreement with the eastward decrease of GPS vector values (with respect to Eurasia) located north of the fault. Our study reveals a high regional earthquake hazard (Mw6.5 to 7.3) in the near future, which adds to the challenge of building the new railroad in such mountainous area.