Microseismicity along Xiaojiang Fault Zone (Southeastern Tibetan Plateau) and the characterization of interseismic fault behavior

• Published in: Tectonophysics Vol. 833; p. 229364
• Main Authors: Zhou, Yijian, Yue, Han, Zhou, Shiyong, Fang, Lihua, Zhou, Yun, Xu, Lisheng, Liu, Ziming, Wang, Teng, Zhao, Li, Ghosh, Abhijit
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 20.06.2022; Elsevier BV
• Subjects: Algorithms; B-value; Conjugates; Detection and location; Earthquakes; Fault zones; Faults; Geological hazards; Global positioning systems; GPS; Interseismic fault behavior; Microseismicity; Microseisms; Satellite navigation systems; Seismic activity; Seismic hazard; Seismicity; Seismology; Structures; Tectonics; Xiaojiang Fault Zone; Tibetan Plateau; Seismic hazard; Microseismicity; Detection and location; Interseismic fault behavior; Xiaojiang Fault Zone; B-value
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2022.229364

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. •We obtained a high-resolution interseismic catalog (2016–2019) for the Xiaojiang Fault Zone.•Widespread microseismicity are detected on off-fault structures, but the major fault shows low seismicity.•The major Xiaojiang fault is strongly locked with low b-value, and could be at a late stage of interseismic loading.•The off-fault structures generate intense microseismicity, repeaters, and high b-values, indicating a weak crustal strength.