山东地区乳山震群双差重定位及发震构造研究

Research on Double Difference Relocation of Rushan Earthquake Swarm in Shandong Area and its Seismogenic Structure

采用双差重定位方法,对2013年10月—2015年10月山东乳山地区1442个ML1.0以上地震事件进行重新定位。重定位后震群震中更加集中,条带状更为清晰,总体呈NW向优势分布;震群震源深度集中在6~10km,其中优势分布深度为7~9km,破裂主要发生在上地壳。通过P波初动法对乳山震群部分ML3.0以上地震的震源机制进行了求解,其震源机制均为走滑型,震源机制的节面A方向与乳山震群重定位分布方向基本一致。综合考虑精确定位结果及较大地震震源机制,初步推测乳山震群发震断层为NW向走滑型隐伏断裂。

Adopting double difference relocation algorithm,we relocated 1442 ML≥1.0 earthquakes in Rushan area from Oct.,2013 to Oct.,2015.The results show that the distribution of epicenters of earthquake swarm become more concentrated after relocation,and the distribution pattern follows a clearer strip with a generally dominant NW.The focal depth ranges from 6 km to 10 km,with the predominant distribution being 7~9 km.The main body rupture happens to the upper crust.By using the P-wave initial motion method,we solved the focal mechanisms of 21 ML≥3.0 earthquakes of the Rushan earthquake swarm.The result shows that the focal mechanism is strike-slip type,the direction of plane A of the focal mechanism is basically consistent with the relocation direction of Rushan earthquake swarm.Taking the precise location results and the focal mechanism of the larger earthquakes into consideration,it can be preliminarily estimated that the seismogenic faults of the Rushan earthquake swarm are NW strike-slip hidden faults.