青海省玛多县“5·22Ms7.4地震”地表破裂与次生灾害发育特征

    The development characteristics of surface fracture and secondary hazards at 5·22 Ms 7.4 earthquake in Maduo County Qinghai Province

    • 摘要: 2021年5月22日2时04分在青海省果洛藏族自治州玛多县发生7.4级地震,为了查明此次地震产生的地表破裂和伴生次生灾害发育特征,调查组采用遥感解译和实地调查方式对地震影响区进行了调查。调查结果显示,在玛多-甘德断裂和昆仑山口-江错断裂之间形成了一条宽约75km、长约230km的活动断裂带,地表新发现地裂缝653条、砂土液化和喷砂冒水点1237个、地震鼓包97个、塌陷坑2个。地表破裂总体呈北西—南东向展布,自西向东出现马尾状分支的现象,东段与玛多-甘德断裂带以一定角度斜交,地裂缝整体走向与昆仑山口-江错断裂走向高度一致。地震地表破裂发育特征显示,此次玛多Ms7.4级地震的发震断裂为昆仑山口-江错断裂,断面整体南倾,性质为左行走滑。此次大地震的发生是在印度板块向青藏高原挤压背景下,巴颜喀拉地块强烈向东挤出构造作用导致其北部走滑断裂发生左旋运动的结果。调查结果为地方政府关于灾区地震灾害损失评估及灾后重建提供了第一手基础资料。

       

      Abstract: At 2:04 on May 22,2021, an earthquake of magnitude 7.4 occurred in Maduo County,Guoluo Tibetan Autonomous Prefecture,Qinghai Province. In order to find out the characteristics of the surface rupture and associated secondary hazards caused by the earthquake,the survey team conducted surveys in the earthquake-affected area by means of remote sensing interpretation and field survey. The survey results showed that an active fault zone with a width of about 75 km and a length of about 230 km was formed between the Maduo-Gande fault and the Kunlun Mountain Pass-Jiangcuo fault; 653 ground fissures,1237 sand liquefaction and sand emitting,water spraying points,97 earthquake bulges and 2 collapse pits were found on the surface. The surface fractures were generally distributed in the north west -south east direction,with horsetail-like branches from west to east; the eastern section was oblique to the Maduo-Gande fault zone at a certain angle. The overall trend of the ground fractures was highly consistent with that of the Kunlun Mountain Pass-Jiangcuo fault. As indicated by the development characteristics of the earthquake surface fracture,the seismogenic fault of the Maduo Ms7.4 earthquake was Kunlun Mountain Pass-Jiangcuo fault,and the fault surface was generally inclined to the south,which featured left strike slip. As the earthquake broke out amid extrusion towards the Qinghai Tibet Plateau by the Indian Plate,the earthquake resulted from sinistral movement at strike-slip fault in the north under the tectonic action of strong eastward extrusion by Bayan Har block. The survey results provide the local government with first-hand basic information on the earthquake disaster loss assessment and post-disaster reconstruction in the disaster area.

       

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