江苏及周缘地区地震精定位与构造意义分析

Analysis on accurate location of earthquakes in Jiangsu and neighboring areas and its tectonic meaning

采用双差定位方法,对江苏地震台网记录到的江苏及邻区地震事件(1990—2009年)重新定位,共获取1020个定位结果,震中平均误差为:南北向0.42 km,东西向0.43 km,垂直向0.53 km。精定位后约94%的地震事件震源深度分布在5—20 km范围内,平均震源深度为12.3 km。震源深度自东向西,从海域向陆域呈现逐渐加深的变化特征。根据构造背景和断裂带分布的不同,分区讨论不同构造部位震源深度分布的特征与差异:沿郯庐断裂带(A)、中东部大陆边缘地区(B)以及苏南茅东断裂带地区(C),震源深度分布具有明显差异,其中C区的α、β、D值最高,分别为0.47、0.66、21 km。此外,精定位结果显示,发生在常熟一张家港地区的小震群,其震源深度自浅至深连续分布,深度区间为5—30 km。

Using double difference location method, we relocated the earthquakes of ML≥1. 0 recorded by the Jiangsu regional seismic network during period of 1990 to 2009, and obtained 1 020 accurately located results. The average error of relocation is 0.42 km in the NS direction, 0.43 km in the EW direction and 0.53 km in the vertically direction. About 94% earth- quakes distributed among the depth of 5 20 km range. The focal depth of the overall varia- tion characteristics from the sea area to the land have gradually deepened. According to the different tectonic setting and fault distribution, we divided Jiangsu area into （A） along the Tancheng-Lujiang fault zone, （B） continental margin in the middle east region and （C） along the Mao-Dong fault zone. The three parts of the focal depth distribution and tectonic characteristics are studied in detail. The results show that the maximum of α,β,D were at the C region, about 0. 47,0. 66,21 km, respectively. Additionally, the relocation results displayed that the earthquake swarm occurred in Changshu-Zhangjiagang region as a whole with clear line-shape characteristics of vertical down continuously extended, about 30 km from 5 km extended.