正断层阶区现今连接模式综合研究——以山西裂谷系口泉断裂禅房阶区为例  

COMPREHENSIVE STUDY OF THE CURRENT CONNECTION MODE OF A NORMAL FAULT STEPOVER:AN EXAMPLE OF THE CHANFANG STEPOVER ON THE KOUQUAN FAULT IN THE SHANXI RIFT SYSTEM,CHINA

作　　者：花春雨 苏鹏[1,2] 石峰 席茜[1] 郭钊吾 HUA Chun-yu;SU Peng;SHI Feng;XI Xi;GUO Zhao-wu(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Taiyuan Continental Rift Dynamics National Field Scientific Observation and Research Station,Taiyuan 030025,China)

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [2]山西太原大陆裂谷动力学国家野外科学研究站,太原030025

出　　处：《地震地质》2024年第4期837-855,共19页Seismology and Geology

基　　金：山西太原大陆裂谷动力学国家野外科学观测研究站项目(NORSTY20-03);中国地震局地质研究所基本科研业务专项(IGCEA2021);财政部改善科研条件专项项目(XG-22-01)共同资助。

摘　　要：正断层阶区有软连接(soft-link)和硬连接(hard-link)2种端元连接模式。判定正断层阶区现今的连接模式不但有助于理解正断层的生长演化过程,也能指示未来正断层上发生的地震是否会在阶区内形成地表破裂,这对于评价阶区内工程场地的地震安全性具有重要意义。判定正断层阶区内是否存在活动的连接断层是区别正断层阶区现今连接模式的直接方法。然而,在多数情况下,由于正断层阶区内的变形量相对小,加上人类活动对阶区内地貌的改造,导致在本以硬连接模式生长的正断层阶区内也很难直接看到断层陡坎,这为判定正断层阶区内是否存在活动的连接断层带来了困难。山西裂谷系是东亚大陆显著的活动裂谷带,也是中国重要的强震带。口泉断裂位于山西裂谷系北部,是大同盆地的西缘边界断裂。口泉断裂在禅房村附近发育一个正断层阶区,文中称之为禅房阶区。文中以口泉断裂禅房阶区为例,通过构造地貌野外调查、地貌数据分析和地质雷达探测研究禅房阶区的连接模式。结果显示,口泉断裂禅房阶区内部存在活动的连接断层,说明禅房阶区的连接方式为硬连接模式。文中研究基于构造地貌野外调查、地貌数据分析和地质雷达探测的综合方法,可有效定位弱活动断层的空间展布,降低单一方法的不确定性。The overlapping area between the ends of adjacent fault segments is known as a fault stepover.The normal fault stepover has two endmember connection modes,i.e.,soft-link mode and hard-link mode.The soft-link stepover’s border faults are connected through a relay ramp,and the border faults’displacements are transmitted through the bending deformation of the relay ramp.The hard-link stepover’s border faults are connected through a breaching fault,and the border faults’displacements are transmitted through the faulting deformation of the breaching fault.Distinguishing the current connection mode of a normal fault stepover can shed light on the evolution stage of the normal fault.It can also indicate the potential earthquake rupture pattern in the stepover,which is important for evaluating the seismic hazard of engineering sites within the stepover.The straightforward technique to distinguish the current connection mode of a normal fault stepover is to determine whether an active breaching fault exists within the stepover.However,in many cases,due to the small amount of accumulated offset and human modification of the breaching fault,it is always hard to observe fault scarps in the field even though the fault stepover is deforming under the hard-link mode.The Shanxi Rift System is a prominent intracontinental rift zone in East Asia.It comprises a series of left-stepping enéchelon grabens bounded by high-angle normal faults.It is distributed in an S-shaped geometry with a narrow,NNE-trending zone in the middle and two broad,NEE-trending extensional zones in the north and south.The Shanxi Rift System is one of the strong earthquake-prone regions in China.Since 780 BC,the Shanxi Rift System has hosted three M8 earthquakes,five M7-7^(3/4)earthquakes,and a series of M6-7 earthquakes.The Kouquan fault is the western border fault of the Datong Basin in the northern part of the Shanxi Rift System.A stepover is developed near the Chanfang village on the Kouquan fault,which we named the Chanfang stepover.In this study

关 键 词：正断层 阶区 连接方式 口泉断裂 山西裂谷系 

分 类 号：P315.2[天文地球—地震学]