Abstract:Based on the GNSS data from 2009-2013 and 2015-2019, the fault locking and fault slip deficit of the Lintan-Tanchang fault before the Minxian-Zhangxian MS6.6 earthquake and Xiahe MS5.7 earthquake were inverted by using Tdefnode negative dislocation method. Combined with the spatial distribution of small earthquakes and GNSS velocity profile results, the characteristics of small earthquake activity and horizontal crustal movement before the earthquake occurred are analyzed, and the future seismic risk of the fault is discussed. The results show that the locations of the two earthquakes were strongly locked before the two earthquakes, the depth of the fault locking was consistent with the hypocenter depth of the two earthquakes, and the fault slip deficit rate was relatively low. Combined with the results of the spatial distribution of small earthquakes, it is found that there was a seismically quiet period before the two earthquakes, and the length of the seismically quiet period is consistent with the length of aftershocks. Based on the GNSS velocity profile, it is shown that the Lintan-Tanchang fault is dominated by thrust compression and sinistral strike-slip movement. The fault slip rate is enhanced after the earthquake compared with before the earthquake. Based on the above anomaly characteristics, it is found that there are strong locked and high slip deficit rate in the eastern part of the Lintan segment to the Minxian-Tanchang segment and the eastern Hezuo segment, and the strong locked fault segments also correspond to a seismically quiet period, future attention should be focused on these two regions.
