渭河盆地东南缘渭南塬前北侧分支断层的浅部结构及晚第四纪活动  

SHALLOW STRUCTURE AND LATE QUATERNARY ACTIVITIES OF BRANCH FAULTS ON THE NORTHERN SIDE OF THE WEINAN TABLELAND IN THE SOUTHEASTERN MARGIN OF THE WEIHE BASIN

作　　者：李晓妮[1] 杨晨艺 李高阳[1] 冯希杰[1] 黄引弟 李陈侠[1] 李苗[1] 裴跟弟 王万合 LI Xiao-ni;YANG Chen-yi;LI Gao-yang;FENG Xi-jie;HUANG Yin-di;LI Chen-xia;LI Miao;PEI Gen-di;WANG Wan-he(Earthquake Administration of Shaanxi Province,Xi'an 710068,China;Xi'an Research Institute,China Coal Technology&Engineering Group Corp,Xi'an 710077,China)

机构地区：[1]陕西省地震局,西安710068 [2]中煤科工集团西安研究院有限公司,西安710077

出　　处：《地震地质》2023年第2期484-499,共16页Seismology and Geology

基　　金：陕西省防震减灾“十二五”重点项目“渭南市活断层探测与地震危险性评价([2011]842)”;“关中地区大震危险性评价”项目;中国地震局地质研究所基本科研业务专项(2022JQ-298);陕西省自然科学基础研究计划青年项目(2022JQ-298)共同资助。

摘　　要：渭南塬前断裂是渭河盆地东南缘一条重要的近EW向的全新世活动断裂,与1556年华县8级特大地震的发生密切相关。该断裂的北分支——渭南塬前北侧分支断层通过渭南市区,查明该北侧分支断层的展布、浅部结构、晚第四纪活动性以及发震能力,对于当地的防震减灾工作具有重要意义。文中通过浅层地震和钻孔联合剖面探测,结合地面地质调查,对渭南塬前北侧分支断层的展布、结构特征以及晚第四纪活动性开展研究。4条测线的浅层地震勘探揭示渭南塬前北侧分支断层与渭南塬前断裂平行展布,两者呈阶梯状正断层结构关系。渭南塬前北侧分支断层错断多套第四纪地层,显示出生长型正断层特征;可识别的上断点埋深为95m以浅,晚更新统的垂直错距为16~20m;在剖面上表现为宽200~1 800m的次级断陷带,具有阶梯状正断层和小型地堑结构。钻孔联合地质剖面揭示渭南塬前北侧分支断层距今19ka以来仍有活动,晚更新世中期以来的平均垂直运动速率为0.07~0.26mm/a。结合地表的断层陡坎和断错地貌现象判定,渭南塬前北侧分支断层与渭南塬前主断层同样具有较强的晚更新世—全新世活动性,不能排除渭南塬前北侧分支断层曾经参与1556年华县8级大地震破裂的可能性,亟需针对其潜在地震危险性和危害性开展相关研究。The Weinan Tableland Piedmont fault is an important near-EW-trending Holocene active fault in the southeastern margin of the Weihe Basin,which is closely related to the occurrence of the 1556 Huaxian M8 earthquake.The northern branch of the fault,the northern branch fault in front of the Weinan tableland,passes through the urban area of Weinan.Therefore,finding out the distribution,shallow structure,late Quaternary activity,and seismic capacities of the northern branch fault are of great significance for local earthquake prevention and reduction.The Weihua fault zone,which is composed of F1 and F2 faults,generally strikes near east-west and has a gentle wave shape on the plane.It is a group of active normal faults rising in the south and descending in the north belt one.The Wei-Hua fault zone can be divided into two segments,east and west,and according to its spatial location and geometric distribution,strike change and the difference in geology and landforms on both sides.The eastern section is distributed in front of Huashan Mountain and is called Huashan Piedmont Fault(F2);the western section is distributed in Piedmont of Weinan tableland and is called Weinan Piedmont Fault(F1).There is a large sub-parallel branch fault about 2km to the north of the Piedmont Weinan tableland fault(F1)in the west section,which is called the branch fault on the north side of the Piedmont Weinan tableland.It is also the boundary fault between the Weinan tabland and the Gushi Sag.The Weinan tableland Piedmont Fault(F1)starts from the Weinan Xihekou in the west and extends eastwards through the Fenghe River to Mayukou,Huaxian County,with a length of about 54km;it strikes NWW from the Mayukou to Chishui River,and nearly EW from the Chishui River to the Fenghe River,the west of the Minhe River is NE to NEE,and it is mostly distributed in the form of broken lines or oblique rows.The fault plane dips northward with a dip angle of 60°~70°.The latest activity of the fault is manifested in the latest terraces and alluvial-pluvial fans f

关 键 词：渭河盆地东南缘 渭南塬前北侧分支断层 断层活动性 浅层地震勘探 钻孔联合剖面探测 

分 类 号：P315.2[天文地球—地震学]