2021年玛多M_(W)7.4地震震中区地表破裂的精细填图及阶区内的分布式破裂讨论  

DETAILED MAPPING OF THE SURFACE RUPTURE NEAR THE EPICENTER SEGMENT OF THE 2021 MADOI M_(W)7.4 EARTHQUAKE AND DISCUSSION ON DISTRIBUTED RUPTURE IN THE STEP-OVER

作　　者：韩龙飞 刘静[1,2] 姚文倩[1] 王文鑫 刘小利 高云鹏[1] 邵延秀 李金阳 HAN Long-fei;LIU-ZENG Jing;YAO Wen-qian;WANG Wen-xin;LIU Xiao-li;GAO Yun-peng;SHAO Yan-xiu;LI Jin-yang(Institute of Surface-Earth System Science,School of Earth System Science,Tianjin University,Tianjin 300072,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Institute of Seismology,China Earthquake Administration,Wuhan 430071,China)

机构地区：[1]天津大学地球系统科学学院表层地球系统科学研究院,天津300072 [2]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 [3]中国地震局地震研究所,武汉430071

出　　处：《地震地质》2022年第2期484-505,共22页Seismology and Geology

基　　金：国家自然科学基金(U1839203,42011540385);中国地震局地质研究所基本科研业务专项(IGCEA1812)共同资助。

摘　　要：同震地表破裂形态的精细刻画可为理解断裂带复杂几何结构、动态破裂过程与破裂机理提供重要信息。2021年5月22日,青藏高原内部青海省果洛藏族自治州玛多县发生了M_(W)7.4地震,这是自2008年汶川M_(S)8.0地震后中国大陆地区发生的震级最大的一次地震。此次地震的同震地表破裂突破了沿线多个阶区、弯折等几何不连续结构,形成了长约158km的同震地表破裂带和多样化的断裂几何形态,其中以震中区段落的地震地表破裂形态最为特殊和复杂。有助于全面认识震中区段落的地震地表破裂形态并深入理解其形成机理,文中基于分辨率约为3cm的航空影像数据,结合野外实地调查资料,完成了本区域地表破裂的精细填图。对地表破裂的类型、分布、几何结构和走向等进行的综合分析表明,震中区的地震地表破裂受阶区几何结构的影响而呈现分布式破裂的特点。并且,震中附近的强震动效应和地震断裂初始发育阶段的影响,进一步造成了该段落分布式地震地表破裂的形态。文中高清再现了震中区的阶区及其附近段落的地震地表破裂特点,对走滑断裂带的分布式同震地表破裂有了更进一步的了解。Detailed mapping of coseismic surface rupture can provide valuable information for understanding the geometrical complexities,dynamic rupture processes and fault mechanisms.Fault geometrical complexities,such as bends,branches,and stepovers are common in strike-slip fault systems and can control the coseismic surface rupture characteristics to a certain extent.Observational studies of surface ruptures in past earthquakes suggested that special rupture characteristics would form distributed ruptures and rupture gaps.The detailed mapping has become an important way to study the surface rupture.According to the China Earthquake Networks Center(CENC),the M_(W)7.4 earthquake occurred at 2:04 PM on May 22,2021,in Madoi County,Qinghai Province.The epicenter is about 70 km south of the eastern Kunlun Fault on the northern boundary of the Bayan Kera block.It is the largest earthquake that hit the Chinese mainland since the Wenchuan M_(S)8.0 earthquake in 2008.After field investigation and rupture mapping on the computer,Yao et al.(2022)estimated that the length of surface rupture of this earthquake is 158 km.Surface ruptures of the M_(W)7.4 Madoi earthquake broke through the geometric discontinuities such as step-overs and bends,and formed various coseismic surface fractures,especially in the middle segment.In the survey of the Madoi earthquake,we rapidly acquired aerial image data using UAV aerial photogrammetry and obtained high-resolution digital orthograph models(DOMs)and digital elevation models(DEMs)using PhotoScan software based on the SfM algorithm processing.Those data provide an opportunity for detailed mapping of seismic rupture and also provide an important reference for fieldwork.Based on high-resolution topographic data,we carried out detailed surface rupture mapping,classification,geometric structure and strike analysis for the~30 km section of the epicenter segment.At the same time,we conducted field work to supplement and proofread the maps.According to the characteristics of surface ruptures in the epice

关 键 词：玛多地震 高分辨率地形数据 震中区 分布式地震地表破裂 破裂初始阶段 

分 类 号：P315.2[天文地球—地震学]