2014年金寨M_L3.9震群序列遗漏地震检测及发震构造分析

针对2014年8月—2015年1月安徽金寨发生的M_L3.9震群,利用匹配滤波技术补充台网目录遗漏的地震事件,再利用波形互相关震相检测技术标定P波和S波到时,进一步采用双差定位方法对震群进行重定位,结合震源机制解等分析此次震群活动可能的发震构造。计算结果显示,通过互相关扫描检测到1376个地震台网常规分析遗漏的地震,数量约为台网目录给出的585个事件的2.35倍。检测到的遗漏地震震级估算为M_L0～2.3,通过震级-频次统计分析,加入遗漏地震后地震目录的完整性在M_L0～1.5范围内有较明显的改善。重定位后地震走时残差更小,水平位置更集中,沿NNE向断裂F和NW向青山-晓天断裂呈现近直立的条带状分布。结合地质构造、震源机制解和水库因素,推测2014年金寨M_L3.9震群可能是由周边水库水下渗引起NW向青山-晓天断裂与NNE向断裂F慢滑动而触发的。

Missed Earthquake Detection and Seismogenic Structure Analysis of the Jinzhai ML3.9 Earthquake Swarm Sequence in 2014

We herein used matched filter technique to supplement missing earthquakes from seismic network catalogue in Anhui Jinzhai M_L3.9 earthquake swarm occurred during August 2014 to January 2015,then we determined P and S wave arrival times using seismic phase detection technology based on waveform cross correlation method,and further used the double-difference location method to reposition the earthquake swarm. Combined with the source mechanism solution,the possible seismogenic structure was analyzed. The results show that 1376 missing earthquakes are detected by cross-correlation scanning,which is about 2.35 times of the 585 events given in seismic network catalogue. The magnitude of detected events is from M_L0 to M_L2.3. By magnitude-frequency analysis the catalog completeness is obviously improved in the range M_L0 to M_L1.5. The relocation result of the newly detected and catalogue listed events shows that the RMS of travel times becomes smaller,the horizontal position becomes more concentrated,showing a nearly erect strip distribution along the NNE-trending fault F and the NW-trending fault Qingshan-Xiaotian. We suggest that the 2014 Jinzhai M_L3.9 earthquake swarm may be triggered by the slow sliding on both fault F and the fault Qingshan-Xiaotian which caused by the infiltration of the surrounding reservoir water.