SEISMOLOGY AND GEOLOGY ›› 2021, Vol. 43 ›› Issue (3): 722-737.DOI: 10.3969/j.issn.0253-4967.2021.03.016

• Special topic on the Yunnan Yangbi MS6.4 and Qinghai Maduo MS7.4 earthquakes • Previous Articles    

SEISMOGENIC FAULT AND COSEISMIC SURFACE DEFORMATION OF THE MADUO MS7.4 EARTHQUAKE IN QINGHAI, CHINA: A QUICK REPORT

LI Zhi-min1), LI Wen-qiao2), LI Tao3,4), XU Yue-ren2), SU Peng3), GUO Peng3), SUN Hao-yue3), HA Guang-hao3), CHEN Gui-hua3), YUAN Zhao-de3), LI Zhong-wu3), LI Xin1), YANG Li-chen1), MA Zhen1), YAO Sheng-hai1), XIONG Ren-wei2), ZHANG Yan-bo2), GAI Hai-long1), YIN Xiang1), XU Wei-yang1), DONG Jin-yuan2)   

  1. 1)Qinghai Earthquake Agency, Xining 810001, China;
    2)Institute of Earthquake Forecasting, China Earthquake Administration, Beijing 100036, China;
    3)State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China;
    4)Lhasa National Geophysical Observation and Research Station, Institute of Geology, China Earthquake Administration, Lhasa 850004, China
  • Received:2021-06-22 Revised:2021-06-26 Online:2021-06-20 Published:2021-07-20

2021年5月22日青海玛多MS7.4地震的发震构造和地表破裂初步调查

李智敏1), 李文巧2),*, 李涛3,4),*, 徐岳仁2), 苏鹏3), 郭鹏3), 孙浩越3), 哈广浩3), 陈桂华3), 袁兆德3), 李忠武3), 李鑫1), 杨理臣1), 马震1), 姚生海1), 熊仁伟2), 张彦博2), 盖海龙1), 殷翔1), 徐玮阳1), 董金元2)   

  1. 1)青海省地震局, 西宁 810001;
    2)中国地震局地震预测研究所, 地震预测重点实验室, 北京 100036;
    3)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;
    4)中国地震局地质研究所, 西藏拉萨地球物理国家野外科学观测研究站, 拉萨 850004
  • 通讯作者: *李文巧, 男, 1978年生, 博士, 副研究员, 主要从事活动构造、 地震工程应用等方面的研究工作, 电话: 010-88015764, E-mail: lwq3278@163.com。
  • 作者简介:李智敏, 男, 1977年生, 2005年于中国地震局兰州地震研究所构造地质学专业获硕士学位, 副研究员, 研究方向为活动构造及其次生灾害, 电话: 0971-6127653, E-mail: minhero_168@126.com。李涛, 男, 1985年生, 博士, 研究员, 主要从事新构造、 活动构造等方面的研究, 电话: 010-62009027, E-mail: litao.410@163.com。
  • 基金资助:
    2021年青海玛多地震科学考察专项、 青藏高原第2次科学考察项目(2019QZKK0901)、 中国地震局地质研究所基本科研业务专项(IGCEA1920, IGCGA1803)、 国家自然科学基金(42072248, U1839203)和中国地震局地震预测研究所基本科研业务专项(2017IES010101)共同资助

Abstract: At 02:04 a.m. on May 22, 2021, a MS7.4 earthquake occurred in the Maduo County, Qinghai Province, China. Its epicenter is located within the Bayan Har block in the north-central Tibetan plateau, approximately 70km south of the eastern Kunlun fault system that defines the northern boundary of the block. In order to constrain the seismogenic fault and characterize the co-seismic surface ruptures of this earthquake, field investigations were conducted immediately after the earthquake, combined with analyses of the focal parameters, aftershock distribution, and InSAR inversion of this earthquake.
This preliminary study finds that the seismogenic fault of the Maduo MS7.4 earthquake is the Jiangcuo segment of the Kunlunshankou-Jiangcuo Fault, which is an active NW-striking and left-lateral strike-slip fault. The total length of the co-seismic surface ruptures is approximately 160km. Multiple rupture patterns exist, mainly including linear shear fractures, obliquely distributed tensional and tensional-shear fractures, pressure ridges, and pull-apart basins. The earthquake also induced a large number of liquefaction structures and landslides in valleys and marshlands.
Based on strike variation and along-strike discontinuity due to the development of step-overs, the coseismic surface rupture zone can be subdivided into four segments, namely the Elinghu South, Huanghexiang, Dongcaoarlong, and Changmahexiang segments. The surface ruptures are quite continuous and prominent along the Elinghu south segment, western portion of the Huanghexiang segment, central portion of the Dongcaoarlong segment, and the Huanghexiang segment. Comparatively, coseismic surface ruptures of other portions are discontinuous. The coseismic strike-slip displacement is roughly determined to be 1~2m based on the displaced gullies, trails, and the width of cracks at releasing step-overs.

Key words: Maduo earthquake, coseismic surface rupture, seismogenic fault, Bayan Har block, Tibetan plateau

摘要: 北京时间2021年5月22日02时04分, 青海省果洛藏族自治州玛多县发生了MS7.4地震, 震中位于巴颜喀拉地块内部, 距地块北边界东昆仑断裂带约70km。 在综合分析震源参数、 余震分布和InSAR反演结果的基础上, 我们第一时间对发震断层和同震地表破裂进行了野外考察。 初步研究表明, 玛多地震的发震断层为NW走向、 左旋走滑的昆仑山口-江错断层, 破裂段为江错段。 地表破裂长160km, 主要由线性剪裂隙、 斜列张裂隙和张剪裂隙、 挤压鼓包、 地震陷坑等多种构造类型组合而成, 在河谷、 沼泽地区伴有大量喷砂冒水、 砂土液化现象和重力滑坡等。 地表破裂带自西向东可依次划分为鄂陵湖南段、 黄河乡段、 冬草阿龙湖段和昌麻河乡段; 不同段之间或走向差别较大, 或以大的拉张阶区分隔。 其中, 鄂陵湖南段、 黄河乡段的西段、 冬草阿龙湖段的中段和昌麻河乡段的地震地表破裂带明显且可连续追踪, 尤以鄂陵湖南段的地表破裂规模最大; 其他段的地表破裂断续展布。 根据冲沟、 道路和拉张阶区裂隙宽度等可确定地表同震位移量为1~2m。

关键词: 玛多地震, 同震地表破裂, 发震断层, 巴颜喀拉地块, 青藏高原

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