2016年门源Ms6.4地震前祁连山周边断层活动分析

基于青藏高原东北缘地区最新的跨断层资料，利用时序曲线分析、断层速率合成分析和垂直形变累积率分析等多种方法进行计算，从不同角度和范围提取2016年门源Ms6.4地震震前异常特征，揭示断层活动。结果显示：1）震中距150 km以内多个场地出现了典型的以加速张性变化为主的短期异常，150~300 km内的异常以趋势变化为主；2）祁连山-海原断裂带上异常场地的空间分布表现出由祁连山断裂带中部集中向东迁移至中东部集中的特征，海原断裂上异常有所增多，此类现象与2003年民乐6.1级地震前的现象极其相似；3）祁连山断裂自2014年以来合成速率偏离正常动态值较远，容易积累应变。垂直形变趋势累积率的计算结果显示，地震震中位于形变积累的高值区。

Activity Analysis of Faults around Qilianshan before the 2016 Menyuan Ms6.4 Earthquake

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.