严家桥—枫沙湖断裂第四纪活动特征

Quaternary Active Features of Yanjiaqiao-Fengshahu Fault

严家桥—枫沙湖断裂是位于郯庐断裂带前陆冲断带的一条重要隐伏-半裸露断裂,沿断裂附近有文字记载以来发生过数次破坏性地震,然而对于该断裂的几何结构、活动性质、活动时代等目前尚无统一认识。在高精度卫星影像解译的基础上,通过详细野外地质调查、典型断层剖面分析及部分断层泥年龄样品测试,研究了严家桥—枫沙湖断裂的几何结构及活动特征。研究发现断裂在深部重力场上表现为NNE向异常条带,自严家桥向南经潘家桥,止于枫沙湖附近,主要表现为东西两支断裂的山前断裂;其最新活动时代为中更新世中期,最新活动可能以走滑为主。结合前人对1585年巢湖5~3/_4级地震及1654年庐江、枞阳间5~1/_4级地震的等震线形态及区域断裂分布的研究,认为这两次地震的发生可能与严家桥—枫沙湖断裂的最新活动有关。

Yanjiaqiao-Fengshahu fault is an important buried or half-naked fault located at the foreland thrust belt of the Tanlu fault zone,and there had happened several destructive moderate-strong earthquakes along the fault according to written records.However,there has still been no consensus of views of the geometric structure of the fault as well as its activity age and characteristics.Based on the interpretation of high-resolution satellite image,we studies the geometric structure and activity characteristics of Yanjiaqiao-Fengshahu fault through the detailed field geological survey,the analysis of typical fault profiles,and the testing of fault gouge age samples.As the investigation shows,the fault is manifested as an abnormal stripe along the NNE direction in the deep gravitational field,and in the area ranging from Yanjiaqiao to Panjiaqiao,and ending near Fengshahu,it mainly assumes the form of a piedment fault of the east and west two-branch faults.The latest activities occurred in the middle Pleistocene and were probably mainly strike-slip ones.Combing with the previous studies on the iso-seismal line of the1585Chaohu M53/4and1654Lujiang-Zongyang M51/4earthquakes and regional fault distribution,it’s concluded that these two earthquakes may be related to the latest activities of Yanjiaqiao-Fengshahu fault.