2014年金寨ML3.9震群序列遗漏地震检测及发震构造分析

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

摘要:

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。

Abstract:

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.