盐城地区小震精定位及构造意义

Precise relocation of small earthquakes in the Yancheng area and associated tectonic implications

采用2009年1月至2018年10月发生在盐城及邻近地区2010次地震事件被141个数字化地震台站记录到的27136条P波和24943条S波到时资料,运用双差定位法对这些小震进行了重新定位,最终得到了1417次小震的定位结果.分析表明,重新定位后的结果相比原始定位的精度有很大改善,建湖震群更加集中于洪泽-沟墩断裂带附近;东台地区的陈家堡-小海断裂带上小震成带分布;射阳地区存在NWW向的断层,此断层可能是区域背景应力场产生的.苏北-滨海断裂活动性最强,发生过多次破坏性地震.建湖-射阳地区的小震震源深度有显著差异,该区可能存在横向不均匀性.研究区内重新定位后小震的震源深度主要分布在5~15 km的范围内,说明盐城及邻近地区地震基本都发生在中上地壳.本文结果对于认识盐城及邻近地区发震断层及深部构造均有重要意义.

We used 27,136 P-waves and 24,943 S-wave arrival times from 2010 earthquakes in Yancheng area recorded by 141 digital seismic stations during January 2009 to October 2018, and relocated these earthquakes by utilizing double difference location algorithm, finally obtained 1417 relocated earthquakes. The results show that the outcome of relocation have improved the accuracy of the original location. The Jianhu earthquake swarm is more concentrated near the Hongze-Goudun fault zone;small earthquakes are concentrated on obvious strips along the Chenjiapu-Xiaohai fault in Dongtai area. There is a NWW fault in the Sheyang area, which may be caused by the regional background stress field. The North Jiangsu-Binhai fault has the strongest activity and many destructive earthquakes have occurred around it. The focal depths of small earthquakes in the Jianhu-Sheyang area are significantly different, and there may be horizontal inhomogeneity in this area. The focal depths of the small earthquakes after relocation in the study area are mostly concentrated in the range of 5~15 km, indicating that the seismogenic layer of the study area is basically located in the middle and upper part of the crust. These results are important for understanding the seismic faults and deep geological structure in Yancheng area.