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Microseismicity along Xiaojiang Fault Zone (China) and the Characterization of Interseismic Fault Behavior
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  • Yijian Zhou,
  • Han Yue,
  • Shiyong Zhou,
  • Lihua Fang,
  • Yun Zhou,
  • Li-Sheng Xu,
  • Ziming Liu,
  • Teng Wang,
  • Li Zhao,
  • Abhijit Ghosh
Yijian Zhou
Department of Earth and Planetary Sciences, UC Riverside

Corresponding Author:[email protected]

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Han Yue
Beijing University
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Shiyong Zhou
Peking University
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Lihua Fang
Institute of Geophysics, China Earthquake Administration
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Yun Zhou
Institute of Geophysics, China Earthquake Administration, Beijing, China
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Li-Sheng Xu
Institute of Geophysics, China Earthquake Administration
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Ziming Liu
Institute of Theoretical and Applied Geophysics, Peking University, Beijing, China.
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Teng Wang
Peking University
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Li Zhao
Peking University
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Abhijit Ghosh
University of California, Riverside
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Abstract

The Xiaojiang Fault (XJF) Zone locates in the southeastern of Tibetan Plateau and defines the boundary between the South China and Sichuan-Yunnan blocks. Historical large earthquakes were hosted on the XJF, though its seismic hazard in the near future is under debate. In this study, we utilize portable broad-band seismic network to unravel the microseismic activities along XJF, and to further investigate the fault structures and their properties. Adopting PALM, a newly developed earthquake detection algorithm, we obtained ~13,000 relocated events. The micro-seismicity reveals widespread off-fault structures showing conjugate geometry, while the major faults present low seismicity. The fault branches conjugate to the main-fault present intensive microseismicity, which hosts repeating events and presents high b-value. Regional GPS stations reflect slips are mostly concentrated along the XJF, while the slip rate on off-fault branches correlates with seismic activities on these structures. Combining with other recent seismological and magnetotellurics evidences, we suggest a low strength on these off-fault structures, which may partially release tectonic stress loading and serve as a barrier for future big earthquakes. On the XJF, the microseismic events are clustered on the fault junctions with low b-value. A special set of clusters between 25°N to 25.5°N show an along-strike variation of depth from 10 to 25-km, imaging the boundary between creeping and locked fault portions. We revisit the seismic hazard problem of XJF, and conclude that XJF is at the late stage of inter-seismic period.