Spatial slip rate distribution along the SE Xianshuihe fault, eastern
Tibet, and earthquake hazard assessment
Abstract
The Xianshuihe (XSH) 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, where the fault splits into three parallel branches:
Yalahe, Selaha and Zheduotang. Precisely quantifying their slip rates at
various timescales is essential to evaluate regional earthquake hazard.
Here, we expand our previous work on the Selaha fault, to the nearby
Zheduotang and Moxi faults, and add observations on the Yalahe fault and
on the newly discovered Mugecuo South fault zone. Using
tectonic-geomorphology approaches with 10Be dating, we had determined
average late Quaternary slip rates of 9.75±0.15 and 4.4±0.5 mm/yr along
the NW and SE Selaha fault, respectively. Using the same methods here,
we determine a slip rate of 3.7-5.4 mm/yr on the Zheduotang fault and of
10.4-14.8 mm/yr on the Moxi fault. This is consistent with the
southeastward slip rate increase we had proposed along the XSH fault
system from 6-8 mm/yr (Ganzi fault) to ~10 mm/yr (Selaha
fault), and >10.4 mm/yr (Moxi fault). We eventually propose
a new model for the SE Xianshuihe fault, where the large-scale Mugecuo
pull-apart basin lies within an even larger scale compressive uplift
zone in the XSH fault’s restraining bend, where the highest peak in
eastern Tibet is located (Gongga Shan, 7556 m). Our slip rates
determination allows to estimate a relatively high regional earthquake
hazard of Mw~7 at present in the SE Xianshuihe fault.