盖州青石岭地震序列发震构造初探

Seismogenic structure of the Qingshiling, Gaizhou, earthquake swarm

  • 摘要: 利用双差定位方法对盖州青石岭震群2012年2月至2015年8月的地震活动进行了重新定位,并使用CAP方法和P波初动法计算了ML≥4.0地震的震源机制解,之后结合盖州地区的地震地质资料,分析了青石岭震群的发震构造.结果表明:青石岭震群在平面上呈NW向分布,地震活动主要分布在6 km×3 km的矩形范围内,震源深度为7—10 km;较大地震的震源机制解的走向与精定位后地震的优势分布方向一致;综合分析双差定位结果、震源机制解和发震区的地震地质等资料,初步认为九寨—盖县北段西北侧存在NW向次级铲式正断层,青石岭震群即为该断层在区域应力场作用下不断地左旋走滑-拉张错动造成的.

     

    Abstract: Using double difference earthquake location algorithm, we relocated the Qingshiling earthquake swarm which lasted from February 2012 to August 2015. We also obtained the earthquake focal mechanism solutions of the swarm by cut and paste (CAP) method and the P-wave first motion method, and then according to the seismo-geological conditions, we discussed the seismogenic structure of the sequence. The results demonstrated that the distribution direction of the relocated earthquakes is NW, and the earthquakes of the swarm mainly distributed in a scope of 6 km×3 km with the focal depths varied from 7 km to 10 km. The strike of some large earthquakes coincided with the predominant distribution direction of the relocated swarm. Based on double difference results, focal mechanisms and local geological conditions, we preliminarily surmised that there lies a listric secondary normal fault of NW trending to the northwest side of the Jiuzhai-Gaixianbei fault, and Qingshiling earthquake swarm may be caused by that listric normal fault which is controlled by continuous left-lateral strike slip motion under regional stress field.

     

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