利用浅层地震反射剖面探测研究大兴断裂北段新近纪—第四纪的构造特征  

RESEARCH ON NEOGENE-QUATERNARY STRATIGRAPHIC STRUCTURE AND SHALLOW TECTONIC FEATURES IN THE NORTH SECTION OF DAXING FAULT ZONE BASED ON SHALLOW SEISMIC REFLECTION PROFILING

作　　者：何付兵[1,2] 徐锡伟[1,3] 何振军 张晓亮 刘立岩[2] 张巍[2] 魏波 倪敬波[2] HE Fu-bing;XU Xi-wei;HE Zhen-jun;ZHANG Xiao-liang;LIU Li-yan;ZHANG Wei;WEI Bo;NI Jing-bo(Institute of Geology,China Earthquake Administration,Beijing 100029,China;Beijing Institute of Geological Survey,Beijing 100095,China;National Institute of Natural Hazards,MEMC,Beijing 100085,China)

机构地区：[1]中国地震局地质研究所,北京100029 [2]北京市地质调查研究院,北京100195 [3]应急管理部国家自然灾害防治研究院,北京100085

出　　处：《地震地质》2020年第4期893-908,共16页Seismology and Geology

基　　金：北京市市级职工创新工作室(城市地质、活动构造与监测);北京市地质调查项目(PXM2018-158203-000014)共同资助。

摘　　要：跨大兴断裂北段的3条浅层二维地震反射剖面,揭示了大兴断裂北段所在区的新近系—第四系结构与断裂结构特征。研究结果表明:大兴断裂北段所在区域的新近系-第四系内可识别出T01-T03、TQ和T11-T13共计7组强反射同相轴,与其下的古近系及更早期的地层呈不整合接触。大兴断裂是一条地壳深度的断裂,其在浅部不同构造位置的产状、断距等有所差异,宏观呈现由SW向NE倾角减缓(80°~60°)、上断点埋深变深(160~600m)、新近系断距(80~0m)减小的特征。在断裂NE末端表现为与三剪运动有关的变形加宽三角带,而不是一条持续的断层。断裂的几何结构和形态揭示其于新近纪—早第四纪仍延续了古近纪的伸展正断活动,晚更新世以来无明显活动,现今沿线发育的地震可能与此构造的关系不大。大兴断裂的北段走向NNE,长约23km,与夏垫断裂呈右阶排列,形成一个长约13km的断裂重叠区。这种断裂组合在伸展构造背景下独立演化,分别控制廊固、大厂次级凹陷的发育,并最终在断裂交接重叠区形成成熟型的转换斜坡。The Daxing Fault is an important buried fault in the Beijing sub-plain,which is also the boundary fault of the structural unit between Langgu sub-sag and Daxing sub-uplift.So far,there is a lack of data on the shallow tectonic features of the Daxing Fault,especially for the key structural part of its northern section where it joins with the Xiadian Fault.In this paper,the fine stratigraphic classifications and shallow tectonic features of the northern section in the main Daxing Fault are explored by using three NW-trending shallow seismic reflection profiles.These profiles pass through the Daxing earthquake(M6¾)area in 1057AD and the northern section of the main Daxing Fault.The results show that seven strong reflection layers(T01—T03,TQ and T11—T13)are recognized in the strata of Neogene and Quaternary beneath the investigated area.The largest depth of strong reflection layer(T13)is about 550~850ms,which is interpreted as an important surface of unconformity between Neogene and Paleogene or basement rock.The remaining reflection layers,such as T01 and TQ,are interpreted as internal interfaces in Neogene to Quaternary strata.There are different rupture surfaces and slip as well as obviously different structural features of the Daxing Fault revealed in three shallow seismic reflection profiles.The two profiles(2-7 and 2-8)show obvious rupture surfaces,which are the expression of Daxing Fault in shallow strata.Along the profile(2-6),which is located at the end of the Daxing fault structure,a triangle deformation zone or bending fracture can be identified,implying that the Daxing Fault is manifested as bending deformation instead of rupture surfaces at its end section.This unique structural feature can be explained by a shearing motion at the end of extensional normal fault.Therefore,the Daxing Fault exhibits obviously different tectonic features of deformation or displacement at different structural locations.The attitude and displacement of the fault at the shallow part are also different to some extent.From

关 键 词：大兴断裂北段 浅层地震 新近纪-第四纪 构造特征 断层活动性 

分 类 号：P315.2[天文地球—地震学]