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EARTHQUAKE ›› 2005, Vol. 25 ›› Issue (1): 58-66.

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Study on faulting behavior and fault-segments for pot- ential strong earthquake risk along the central- southern segment of Xianshuihe fault zone based on current seismicity

YI Gui-xi1, FANG Jun1,2, WEN Xue-ze1   

  • Received:2004-03-24 Revised:2004-07-05 Online:2005-01-31 Published:2021-11-10

Abstract: In this paper, using the present seismic data from the regional network for the last 25 years and combing with the analysis of depth distribution of relocated hypocenters and historical strong earthquake sources along the central-southern segment of the Xianshuihe fault zone, the authors have studied the current faulting behaviors on different segments of the fault zone, and preliminarily identified the risky fault-segments on which potential strong earthquakes would occur in the near future, based on distribution of b-values along the fault zone and various combinations of values of multiple seismicity parameters on the different fault-segments. The results show that the studied fault zone currently has six segments showing different faulting behavior. Of which, the Daofu segment has tended to be locked again since the 1981 strong earthquake, and the reason could be that the fault plane there probably has an asperity. It seems to need more time to build-up strain. The Bamei segment is now situated in the state of relative rest under middle to high stress, such a state can be explained as that the fault plane is being on its new stage for stress accumulation. The Tagong segment has no strong earthquake occurred for 255 to 300 years. And now is behaving locked under relatively high stress. A gap of current small-quakes on the profile of hypocenter depth seems to outline the locked fault plane of this segment. These suggest that the Tagong segment should be the most possible section of the fault zone for a potential strong earthquake occurring in the near future. The Kangding and Moxi segments are behaving weak slipping of sparse small-quakes and slipping of denser small-quakes respectively, under middle to low stress, showing that the fault planes have not yet re-coupled since the latest large earthquake rupture on the both segments. The Shimian segment displays frequent small-quake activity under middle to high stress, which is probably associated with the locality being at a junction area of several branch faults.

Key words: Seismicity parameter, Faulting behavior, Strong-earthquake risk, Xianshuihe fault zone

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