北京平原大兴凸起东缘断裂全新世活动的新认识  

NEW INSIGHT ON THE HOLOCENE ACTIVITY OF THE EASTERN MARGINAL FAULT OF DAXING UPLIFT, BEIJING PLAIN

作　　者：李正芳[1] 李彦宝[1] 周本刚[1] 朱国军[2] 刘保金[2] 吴健 LI Zheng-fang;LI Yan-bao;ZHOU Ben-gang;ZHU Guo-jun;LIU Bao-jin;WU Jian(Key Laboratory of Seismic and Volcanic Hazards,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Geophysical Exploration Center,China Earthquake Administration,Zhengzhou 450002,China;China Earthquake Disaster Prevention Center,Beijing 100029,China)

机构地区：[1]中国地震局地质研究所,中国地震局地震与火山灾害重点实验室,北京100029 [2]中国地震局地球物理勘探中心,郑州450002 [3]中国地震灾害防御中心,北京100029

出　　处：《地震地质》2021年第6期1671-1681,共11页Seismology and Geology

基　　金：地震灾害风险普查项目“京津高震级震源排查及全国潜源数据库建设”资助。

摘　　要：大兴凸起东缘断裂位于北京平原的东南部,是控制大兴凸起与廊固凹陷的边界断裂,向N与控制大厂凹陷的曾发生1679年8级地震的NNE向夏垫断裂斜接,总体走向NE,倾向SE。以往的研究认为该断裂断错的最新地层为第四系中更新统,其不属于晚第四纪以来的活动断裂。文中在高精度浅层地震勘探的基础上开展了高密度钻孔联合地质剖面探测,获得了该断裂晚第四纪以来具有明显活动的证据。该断裂在钻孔联合地质剖面中显示出正断活动特征,一套厚约7m的粉砂质黏土标志层在其断层下盘的顶界面埋深约为74m,而在其上盘的顶界面埋深约为102m,位错量约为28m,且可在其中的2个钻孔中分别深54.2m和39.4m的岩芯内发现断层滑动面。水平距离为2m的2个钻孔的标志层顶面埋深分别为8m和10m,位错量为2m,结合2个钻孔岩芯的变形特征分析认为断层的上断点埋深可能更浅。根据邻近已有钻孔的年代学资料推断,该断裂属于全新世活动断裂。文中研究改变了大兴凸起东缘断裂带并非为活动断裂的认识,此新发现不仅对大兴凸起东缘断裂带的强震危险性和北京市地震灾害风险的认识具有重要的应用价值,也对华北地区晚新生代以来断裂发展演化及其深浅耦合特征研究具有科学意义。The eastern marginal fault of Daxing Uplift is located in the southeast of the Beijing Plain, which is a boundary fault that controls the Daxing Uplift and the Langgu Sag. It intersects obliquely with the NNE-trending Xiadian Fault in the north where a magnitude 8 earthquake occurred in 1679. The overall strike of the fault is northeast, dipping southeast. Previous studies have suggested that the youngest stratum of the fault is the Mid Pleistocene of the Quaternary and it is not an active fault since the Late Quaternary. Based on high-precision shallow seismic exploration data, this study carried out high-density composite drilling geological section surveys and obtained evidence of obvious activity of the fault since the Late Quaternary. The fault is shown as an active normal fault in the composite drilling geological section. The top of the footwall of the fault is the 7 m-thick silty clay marker layer buried at the depth of 74 m and the top of the hanging wall is 102 m deep, the amount of dislocation is about 28.0 m. Fault slip surfaces were found in the cores of two of the boreholes, with depths of 54.2 m and 39.4 m, respectively. The buried depths of the top surface of the marker layer in the two boreholes with a horizontal distance of 2 m are 8 m and 10 m, respectively, the dislocation amount is 2 m. Combined with the observation of core deformation characteristics of the two boreholes, it is believed that the buried depth of the upper breakpoint of the fault may be shallower. This research has changed the understanding that the fault zone on the eastern margin of the Daxing Uplift is not active. This new discovery not only has great application value for understanding the risk of large earthquakes of this fault zone and the risk of earthquake disasters in Beijing, but also has scientific significance for the study of fault development and evolution and the deep-shallow coupling process in North China since the late Cenozoic. The main knowledge gained is as follows: 1)Through high-precision shallow seismic

关 键 词：浅层地震勘探 钻孔联合地质剖面探测 全新世活动断裂 大兴凸起东缘断裂 

分 类 号：P315.2[天文地球—地震学]