| 青海玛多“5·22”MS7.4级地震的同震地表破裂特征、成因及意义 |
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| 引用本文： | 盖海龙,姚生海,杨丽萍,亢太波,殷翔,陈庭,李鑫.青海玛多“5·22”MS7.4级地震的同震地表破裂特征、成因及意义[J].地质力学学报,2021,27(6):899-912. |
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| 作者姓名： | 盖海龙 姚生海 杨丽萍 亢太波 殷翔 陈庭 李鑫 |
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| 作者单位： | 1.青海省地震局, 青海 西宁 810001 |
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| 基金项目： | 中国地震局青海玛多MS7.4级地震科学考察专项；中国地震局地震科技星火计划项目（XH20061Y）；青海省地震科学基金项目（2019A03） |
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| 摘 要： | 2021年5月22日2时4分在青海省果洛藏族州玛多县境内发生MS7.4级地震，此次玛多MS7.4级地震是2008年汶川MS8.0级大地震之后中国震级最大的一次地震，及时查明其同震地表破裂展布及特征，对于正确认识发震构造和区域防震减灾具有重要意义。根据震后现场调查，结合高分辨率卫星遥感图像的解译分析、余震数据和典型地震地表破裂的无人机低空摄影测量等结果，初步获得了此次地震6处典型地震地表破裂的特征。结果发现:此次玛多地震的地表破裂主要沿已知的东昆仑断裂带的南侧分支断裂昆仑山口-江错断裂的东南段分布，分析表明其中的江错断裂应是此次地震的发震断层；同震破裂的西段总体走向275°~300°，主要表现为挤压鼓包和雁列式张裂隙的斜列组合，其中江错贡麻段至江多村段出现了明显的1.4~0.8 m的垂直位移，指示该段可能具有较明显的正断层成分；中部黄河乡段主要由一系列呈左阶斜列的北西向P剪切裂缝和右阶雁行排列的北东向张裂隙构成，走滑位移较小；而东段地表破裂出现了多个分支，其中北支昌马河段主要由一系列雁行排列的张裂隙组成，总体走向为260°，与断裂西段的走向明显不同；地震造成的最大左旋位移出现在西段的错尔加拉破裂段，约2.8 m，指示此次地震地表破裂带的走滑位移主要呈从西向东的单侧扩展-衰减特征。考虑到此次玛多地震出现在东昆仑主干断裂南侧的巴颜喀拉地块内部，表明该地块内部具有发生7级以上大地震的能力，因此，巴颜喀拉地块内部强震活动的孕震条件和机理应该是未来需要进一步关注的科学问题。
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| 关 键 词： | 玛多MS7.4级地震 地震地表破裂 江错断裂 东昆仑断裂带 巴颜喀拉块体 |
| 收稿时间： | 2021/6/25 0:00:00 |
| 修稿时间： | 2021/9/9 0:00:00 |
Characteristics and causes of coseismic surface rupture triggered by the "5.22" MS 7.4 Earthquake in Maduo,Qinghai, and their significance |
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| GAI Hailong,YAO Shenghai,YANG Liping,KANG Taibo,YIN Xiang,CHEN Ting,LI Xin.Characteristics and causes of coseismic surface rupture triggered by the "5.22" MS 7.4 Earthquake in Maduo,Qinghai, and their significance[J].Journal of Geomechanics,2021,27(6):899-912. |
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| Authors: | GAI Hailong YAO Shenghai YANG Liping KANG Taibo YIN Xiang CHEN Ting LI Xin |
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| Institution: | 1.Qinghai Earthquake Agency, Xining 810001, Qinghai, China2.National Field Observation and Research Station for Geodynamics in the Qinghai-Tibet Plateau, Golmud 816000, Qinghai, China3.School of Geodesy and Geomatics, Wuhan University, Wuhan 430070, Hubei, China |
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| Abstract: | An MS 7.4 earthquake occurred in Maduo County, Guoluo Tibetan Prefecture, Qinghai Province at 02:04 on May 22, 2021(Beijing time), which is the largest one in China after the 2008 Wenchuan MS 8.0 earthquake. Finding out the distribution and characteristics of its coseismic surface rupture in time is of great significance for the identification of seismogenic structure, regional earthquake prevention and disaster reduction. Combining the post-earthquake field investigation with the results from the interpretation and analysis of high-resolution satellite remote sensing images, aftershock data and UAV low altitude photogrammetry, we got a preliminary judgment on the characteristics of six typical seismic surface ruptures. Firstly, the surface rupture caused by the Maduo earthquake is mainly distributed along the southeastern segment of the known South Branch of the East Kunlun fault zone, the kunlunshankou-Jiangcuo fault. It indicates that the Jiangcuo fault should be the seismogenic fault of the earthquake. Secondly, the western segment of the coseismic rupture with an overall strike of 275°~300°, is mainly manifested as an inclined combination of compressive bulges and echelon tensile fractures. There is a significant vertical displacement of 1.4~0.8 m between the Jiangcuogongma section and the Jiangduocun section, indicating that the western segment may have obvious normal fault components. The huanghexiang section in the middle is mainly composed of a series of NW-trending P shear fractures with left-order oblique and NE-trending tensile fractures with right-order en echelon, with small strike slip displacements. The Changma reach of the North Branch is mainly composed of a series of en echelon fractures, with the overall strike of 260°, The strike of the fault is obviously different from that of the western segment of the fault. Thirdly, the maximum left lateral displacement caused by the earthquake occurred in the Cuoerjiala rapture section of the western segment, about 2.8 m, indicating that the strike slip displacement of the surface fracture zone of the earthquake is mainly characterized by unilateral expansion attenuation from west to East. The fact that the Maduo earthquake occurred in the Bayan Har block on the south side of the East Kunlun main fault demonstrate the possibility of earthquake with magnitude 7 or above in this block. Therefore the seismogenic conditions and mechanism of strong earthquake activity in the Bayan Har block should be a scientific issue that needs further attention. |
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| Keywords: | Maduo MS 7 4 earthquake earthquake-triggered surface rupture Jiangcuo fault East Kunlun fault zone Bayan Har block |
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