利用波形互相关方法识别分析灌县-安县断裂重复地震

Detection and analysis of repeating earthquakes in Guanxian--Anxian fault by using waveform cross-correlation

以中国地震台网中心地震目录中的事件为模板地震,通过滑动窗口的波形互相关方法对布设在灌县—安县断裂周边17个流动地震台的连续地震记录进行处理,识别ML0.0以上的重复地震.然后使用结合波形互相关技术的双差算法对这些地震进行重定位,获得了243次地震的重定位结果.结果表明:在研究时段内,灌县—安县断裂的地震活动性呈减弱趋势;地震震源的优势分布深度为5—15km,震源深度剖面显示地震呈高角度向西倾斜分布;地震震中沿NE向分布,与龙门山前山断裂的走向基本一致;研究区内南、北两段的地震活动性及b值存在差异,这可能与龙门山断裂带中段区域应力方向由南到北发生的WNW向到ENE向转换的构造作用密切相关.

By taking earthquakes from China Earthquake Networks Center cata-log as template events,we detected repeating earthquakes down to ML 0.0 from continuous waveforms recorded by 17 portable seismic stations deployed near the Guanxian--Anxian fault through a sliding-window cross-correlation tech-nique.Then,based on double-difference algorithm combined with waveform cross-correlation,243 of the detected earthquakes were relocated.The results indicate that seismicity of Guanxian-Anxian fault became weaker during the studied period.The predominance distribution of focal depth is 5—15 km and the depth profile reveals that focal depth distributes in westward dipping with a high angle.The epicenters of these earthquakes are distributed in NE direction, which coincides with the strike of front-range fault of Longmenshan fault zone. There are differences in seismicity and b value between the northern and south-ern segments in the studied region,which may be related to regional stress field of the middle segment of Longmenshan fault zone where directions of stress transfer from WNW to ENE from south to north.