Late Quaternary slip-rates along the Moxi and Zheduotang segments of the
SE Xianshuihe fault, eastern Tibet, and geodynamic implications
Abstract
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.