2013年8月河北蔚县小震群遗漏地震检测与发震构造分析

Missing earthquakes detection and seismogenic structure of the Yuxian earthquake swarm in August of 2013

华北地区近年来小震群活动频繁,在有数字波形记录的中强地震相对缺乏的背景下,小震群发震构造精细研究可为华北地区地震危险性分析和地震趋势判断提供重要依据.本文利用匹配滤波技术对2013年8月22—25日河北蔚县小震群遗漏地震事件进行检测,并通过地震精定位和震源机制求解分析此次震群的发震构造.计算结果显示,通过互相关扫描检测到18次被地震台网常规分析遗漏的地震,约为地震目录给出的13次地震事件的1.38倍.该震群发震构造有北东向和北西向两组断裂,震群活动前期以北东向构造活动为主,后期地震主要发生在北西向构造,北西向构造在此次震群活动中地震频度和强度均高于北东向构造.震源机制计算结果显示北西向构造发震机制以正断拉张为主.

The increasing seismicity of small earthquake swarms have been ob-served in North China area during recent years.Due to the lack of digital wave-form recordings of large earthquakes in this area,detailed seismogenic structure analysis of earthquake swarms is of significance to seismic risk analysis and earthquake tendency judgement.We herein used matched filter technique to de-tect missing earthquakes in Yuxian small earthquake swarm occurred during August 22nd to 25th,2013.By the technique we detected 18 missing earth-quakes,which are about 1.38 times of 13 listed in the catalog.The seismogenic structure of the earthquake swarm can be divided into two parts.One is an NE-trending fault and more active in the early time of this earthquake swarm;the other is an NW-trending fault on which more earthquakes occurred in the later time.The seismicity is much stronger in the NW-trending fault than that in the NE-trending fault.According to focal mechanism of two lager earthquakes in the swarm,it is suggested that the mechanism of earthquakes occurred on the NW-trending fault are dominated by normal slip.