2013年3月涿鹿微震群遗漏地震事件检测和发震构造分析

Missing earthquakes detection and seismogenic structure analysis of the Zhuolu micro-earthquake swarm in March 2013

震群活动时,短时间发生大量地震,不同地震事件的记录波形相互交叠影响,易造成地震目录的遗漏,对震群发震构造分析等研究带来不利的影响.本文针对2013年3月3日至5日在河北涿鹿发生的微震震群,利用匹配滤波技术,以地震台网观测目录所记录地震事件的波形为模板,在连续波形记录中搜索与模板相似的信号,从而检测台网目录遗漏的地震.利用波形互相关标定新检测到地震事件的P波和S波到时,进而对其震中位置和震级做出估计.计算结果显示,通过互相关扫描检测到52个地震台网常规分析遗漏的地震,约为地震目录给出的45个事件的1.16倍.检测到的遗漏地震震级估算为M_L0.1~0.9,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_L0.3~0.8范围内有较明显的改善.根据地震事件精定位结果,推测此次震群的发震构造为北西走向倾角较大的断层,施庄断裂为发震构造的可能性较大.

It easily happens that some earthquakes are missing in existing catalog of earthquake swarm because a large number of earthquakes occurred in a short time that makes waveform recordings of different earthquake events overlap,which has an adverse effect on seismogenic structure analysis.In this paper,we used matched filter technique to detect missing earthquakes in Zhuolu micro-earthquake swarm occurred on March 3 to 5,2013.Using this technique we selected event waveform recordings in catalog as templates,and searched signals similar to the templates in continuous waveform.Then we determined P and S wave arrival times using crosscorrelation to estimate the epicenter and magnitude of detected events.By the technique we detected 52 missing events,which are about 1.16 times of 45 events listed in the catalog.The magnitude of detected events is from M_L0.1 to 0.9.By magnitude-frequency analysis the catalog completeness is obviously improved in the range M_L0.3 to 0.8.According to the relocation result of the newly detected and catalog listed events,we suggest that the seismogenic fault of Zhuolu micro-earthquake swarm is a NW-trending steeply dipping fault structure,may be the Shizhuang Fault.