Abstract:The across-fault data of the Qilianshan-Haiyuan fault zone presents obvious precursory anomalies before the Menyuan Ms6.4 earthquake. We study deformation phenomena and activities of faults around Qilianshan before the earthquake. Based on the latest across-fault data in the northeastern margin of Tibet plateau, and by using a variety of methods, including temporal curve analysis, the fault rate of the synthetic analysis method, and the vertical deformation rate, this article extracts anomaly characteristics and reveals fault activity from different angles and scopes. The results are as follows: (1) Within 150 km epicentral distance, multiple sites present typical short-term anomalies, which are mainly accelerated and extensional changes; within 150-300 km, the anomaly type gives priority to trend variation. (2) The spatial distribution of anomaly stations shows that anomaly stations, concentrated in the middle of Qilianshan fault, have the tendency to migrate to the east and concentrate in the middle-eastern region. At the same time, the anomaly in Haiyuan has increased. These phenomena are extremely similar to those before 2003 Minle Ms6.1 earthquake. (3) From 2014, the synthetic rate of Qilianshan fault deviates from the value of the normal far away, which means strain is easy to accumulate here. Further, according to results of vertical deformation trend accumulation rate, the earthquake epicenter is located in the high value area of deformation accumulation. So the occurrence of the earthquake had a certain degree of inevitability.
LI Yuan,LIU Xia,LIU Xikang et al. Activity Analysis of Faults around Qilianshan before the 2016 Menyuan Ms6.4 Earthquake[J]. jgg, 2016, 36(4): 288-293.