桑干河南山前断裂活动特征

The Active Characteristics of the Piedmont Fault South of Sanggan River

一、引言京西北地区属“首都圈”地震重点监视区,走向NEE的断裂呈右行斜列分布于全区,是控制区内构造格局的主干断裂。它们控制着山西断陷带北段NEE向断陷盆地的形成和发展,与地震活动密切相关(图1)。因此,研究NEE向断裂的特征,对于山西断陷带的形成和京西北地震危险性的评价,无疑具有重要意义。从图1看,桑干河南山前断裂(F5)为山西断陷带北段NEE向断裂中规模最长的一条,其西段先后于1989年10月和1991年3月发生了两次中强地震群,震级分别为M6.1和M5.8,均与该断裂的活动有关。该断裂西起麻峪口以西,向东经徐家堡、南徐村、马家窑,至石匣附近消失,全长130多公里。在断裂延伸范围内。

The piedmont active fault south of Sanggang River is the largest fault of ENE-trending faults in the northern part of Shanxi down-faulted basin belt. Based on the analysis of the evidence available, we have studied in detail the geological history, segmentation and structural features, the vertical dislocation of the fault since the Late Tertiary, as well as their relation to the seismicity.