2022年青海门源MS6.9地震地表破裂特征分类及震害分析

Classified surface rupture characteristics and damage analysis of the 2022 MS6.9 Menyuan earthquake,Qinghai

  • 摘要: 为了深入分析2022年1月8日青海门源MS6.9地震引发的不同类型地表破裂特征及震害现象,本文依据沿此次地震地表破裂带进行的野外实地考察和无人机航拍解译,将破裂带沿线的典型同震地表破裂特征归纳为:① 多种典型几何细结构,包括雁列状次级破裂、左旋左阶拉张区、左旋右阶挤压区以及树枝状、网状破裂等;② 多种地貌标志物水平位错,包括牧区围栏、车辙印、动物脚印和冲沟冰面的左旋断错等;③ 多种类型垂直破裂,如逆冲型地震陡坎和正断型地震陡坎;④ 多种类型挤压破裂,如挤压脊和挤压鼓包;⑤ 不同类型张性裂缝带,如纯张性裂缝带和张剪性裂缝带。将地震引发的地质及工程震害现象归纳为:① 跨地震断裂带的边坡垮塌失稳;② 跨地震断裂带的公路、桥梁和隧道损坏;③ 地震断裂带附近区域的冰面鼓包、公路裂隙等形变现象。此外,对上述现象的展布特征和成因机制进行了分析讨论,并强调了加强跨活动断裂带时工程抗断及近断层强地面运动的抗震设防的重要性。

     

    Abstract: At 01:45 on January 8, 2022, a MS6.9 earthquake occurred in Menyuan County, Haibei Tibetan Autonomous Prefecture, Qinghai Province. The epicenter was located at (37.77°N, 101.26°E) in Lenglongling area of the central Qilian mountains, with a focal depth of 10 km. According to the comprehensive results of field investigation and aerial image interpretation by unmanned aerial vehicle (UAV), the seismogenic fault of this earthquake undertakes a sinistral strike-slip motion, with a slight thrust component. The surface rupture zone of this earthquake is composed of the north main rupture zone located at the west end of Lenglongling fault and the southwest secondary traction rupture zone located at the east end of Tuolaishan fault. A series of extensional step-overs, sinistral displacements, tensional fractures, compressed bulges, and compressed ridges were formed along the surface rupture zone, resulting in damage to the Lanzhou-Ürümqi high-speed railway tunnels and bridges and the suspension of train services. In order to comprehensively analyze the different types of surface fracture features and seismic damage caused by this earthquake, field investigations and aerial interpretation using UAV were conducted along the rupture zone. As a result, typical coseismic surface fracture features along the rupture zone were categorized as follows: ① Various typical geometric structures, including echelon secondary rupture, sinistral extensional step-overs, sinistral compressed step-overs, dendritic and netlike forked rupture, etc; ② Horizontal displacement observed in various geomorphic markers, such as left-lateral dislocations in pastoral areas, truck trace, animal footprints, and gullies and gully ice; ③ Various types of vertical rupture, such as thrust seismic scarps and normal seismic scarps; ④ Various types of compressed rupture, such as compressed ridges and compressed bulges; ⑤ Different types of tensional crack zones, including pure tensional cracks and tensional-shear cracks. The geological and engineering seismic damage caused by the earthquake can be summarized as follows: ① Slope instability across the earthquake fault zone; ② Damage to highways, bridges, and tunnels across the earthquake fault zone; ③ Seismic deformation such as ice bulges and highway cracks in the areas near the earthquake fault zone. In addition, with the analysis and discussion on the distribution characteristics and formation mechanisms of the phenomena above mentioned, we should emphasize the importance of strengthening engineering anti-rupture fortification when engineering constructions cross active faults.

     

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