2016-01-21青海门源MS6.4地震震前应力降变化特征研究

利用甘肃省数字地震台网记录的波形数据，采用Atkinson多台多震计算非弹性衰减系数方法和Moya遗传算法，计算2016年门源MS6.4地震震前3 a震源区及周围地区157个ML2.0以上地震的应力降参数，应力降值分布在0.02~10.86 MPa，平均值为1.67 MPa。结果显示，应力降高值区主要集中在皇城-双塔断裂与冷龙岭断裂之间，与研究区内中强地震活动范围具有很强的一致性；2013年肃南-门源交界MS5.1地震前数月开始出现显著的应力降高值，震后逐渐下降，直到2016年门源MS6.4地震发生前，应力降总体处于较低水平，但在MS6.4地震前半年左右，应力降月均值出现两次高值异常，与门源地震具有一定的对应关系。

Study of the Spatial and Temporal Distribution Characteristics of StressDrop before the January 21, 2016 MS6.4 Menyuan Earthquake

Using the Moya method on the waveform data recorded by the Gansu digital seismic network, we calculate the stress drop of 157 earthquakes with ML≥2.0, occurring in Menyuan area before the January 21, 2016 Menyuan MS6.4 earthquake. The results show that the stress drop ranges from 0.02 MPa to 10.86 MPa with an average value of 1.67 MPa. The earthquakes with high stress drop are mainly distributed between Huangcheng-Shuangta and Lenglongling fault zones, and the area is in harmony with the active area of moderate-strong earthquakes. It is found from analyzing the temporal distribution of stress drop that obvious stress high drop values appear before the MS5.1 earthquake. The stress drop of earthquakes gradually decreases and are generally at a low level after the MS5.1 earthquake. About half a year before the MS6.4 earthquake, twice high-value anomalies of the monthly mean values of stress drop appear, showing some relationship with Menyuan earthquake.