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Systematic search for repeating earthquakes along the Haiyuan fault system in Northeastern Tibet
  • Yangfan Deng,
  • Zhigang Peng,
  • Jing Liu-Zeng
Yangfan Deng
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences

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Zhigang Peng
Georgia Institute of Technology
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Jing Liu-Zeng
Institute of Surface-Earth System Science, Tianjin University
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Repeating earthquakes have been found at many faults around the world, and they provide valuable information on diverse faulting behavior at seismogenic depth. The Haiyuan fault is a major left-lateral strike-slip fault along the northeastern (NE) boundary of the Tibetan Plateau. Two great earthquakes (1920 Haiyuan, 1927 Gulang) have occurred on this fault system, but the section between the ruptures of the two earthquakes, also known as the Tianzhu seismic gap, remains unbroken. Shallow creep has been observed from geodetic data at the eastern end of the seismic gap. However, the driving mechanism and depth extent of shallow creep are not clear. Here we conduct a systematic search for repeating earthquakes in NE Tibet based on seismic data recorded by permanent stations in ten years (2009-2018). Based on waveform cross-correlations and subsequent relocations, we find several repeating earthquake clusters at Laohushan section. This is consistent with the shallow creep inferred from the geodetic data, indicating repeating earthquakes can be driven by nearby aseismic slip. ~300 repeaters were found within clusters of intense seismicity near the rupture zones of the 1927 M8.0 Gulang and 2016 M6.4 Menyuan earthquakes. Relocation of events in the cluster near the Gulang earthquake delineates two possible unmapped faults orthogonal to the Haiyuan fault. In addition, we also identify several repeating earthquakes generated by mining activities with different waveforms and occurrence patterns. Our study suggests that repeating earthquakes around the Haiyuan fault are mostly driven by postseismic relaxation process associated with 1920 Haiyuan and 1927 Gulang earthquakes.
Jul 2020Published in Journal of Geophysical Research: Solid Earth volume 125 issue 7. 10.1029/2020JB019583