大同窗视应力时变特征浅析

利用山自皂、恒山和阳原地震台记录,计算大同窗2001年至2015年6月小震波形视应力,并消除震级影响,获得大同窗小震差视应力随时间的变化结果。结果显示,在山西带和张渤带10次M_L 5左右地震前,差视应力震前5—517天出现明显的高值异常,震后恢复到背景应力水平。结合山自皂台(SZZ)记录的介质品质因子Q_m数值,差视应力和介质品质因子Q_m在10次M_L 5左右地震前呈现超出1倍均方差的准同步高值变化,可见区域应力和介质变化对中强地震孕育有一定反映。

Analysis on time-variation characteristics of the apparent stress of Datong window

In the paper, the apparent stress of Datong window through SZZ, HSH and YAY stations is calculated and the differential apparent stress after eliminating the influence of magnitude is obtained, using the waveform data of small earthquakes from 2001 to June, 2015. The results show that:the obvious high value anomalies of differential apparent stress occurred 10 times before 5 days to 517 days of M_L 5 earthquakes in Shanxi seismic belt and Zhangjiakou-Bohai seismic belt, and then recovered to background stress level after the shocks. Combined with the results of medium quality factor (Q_m) recorded by SZZ station, the differential apparent stress and medium quality factor(Q_m) presented the synchronous high value process which were the high values over 1 times mean square error. The variation of regional stress and medium probably reflects the mid-strong earthquakes preparation process.