摘要
强震极易诱发山区灾变性的泥石流过程,但需辅以必要的地貌、地质、水文或气候条件。2023年积石山地震诱发的青海省民和县中川乡泥石流,因其导致大量人员伤亡而备受关注。基于对中川乡泥石流沟谷及其周边区域的综合考察,包括地貌与第四纪地质特征、天然剖面、泥石流物源和堆积物的颗粒度、颗粒形状特征,以及灾前卫星影像和灾后多型号无人机航摄的多尺度地貌形态等,文章对灾害过程特征、影响因素以及未来防控进行初步的分析和讨论。泥石流在沟谷处的侵蚀程度、堆积厚度及空间分布等特征表明,物源区主要集中在草滩村上游右岸支沟源头。物源区地层丰富的细砂和传统提灌耕作方式,为强震动下滑塌触发提供了有利条件。现场调查表明,物源主要通过群发式浅层(2~3 m)滑塌进行补给,并在运移过程中不断破碎和分散;浅部稳定隔水层的存在和泉水的出露,为源区物质提供持续的水源补给,最终形成流动性的泥石流。灾前流通区谷地横、纵剖面复杂,局部存在小水塘和沟道阻塞的情况,增加了泥石流的阵发性和破坏能力。现场残余堆积物和淤泥痕迹的空间分布特征表明,本次泥石流具有典型的栓流式特征,表现出黏度极大的特点。拥堵导致泥石流淤高和规模持续扩大,持续增加的势能最终导致泥石流冲破谷地障碍继续流动,沿途侵蚀和堆积时有发生。堆积区地形的进一步展开,导致泥石流更容易发生分散和堆积,因此,位于堆积区谷地内的民宅受灾最为严重。此外,由于寒冷天气和夜半发震,以及群众对灾害性质缺乏认知等原因,也在一定程度上加剧了本次泥石流灾害的严重程度。鉴于黄河上游地质构造环境类似于官亭盆地的中小盆地众多,人居环境及人地关系也都相近,可结合本次灾害特点,有步骤地开展灾害调查和排查工作。在此基础上,针对已识别的高风险隐患点,定期开展巡查排查,加强重大灾害风险的预测和预警。同时,加强宣传和科普,提升公众对地震及链生灾害的科学认知水平。
Strong earthquakes can easily trigger catastrophic debris flow in mountainous areas,but these events also require specific geomorphological,geological,hydrological,or climatic conditions.The debris flow in Zhongchuan Township,Minhe County,Qinghai Province,caused by the Jishishan M_(S)6.2 earthquake in 2023,has attracted significant attention owing to its high casualty rate.A comprehensive investigation was conducted on the debris-flow ravines and surrounding areas in Zhongchuan Township.This included on-site surveys of geomorphology and Quaternary geological characteristics,observations of natural profiles,grain-size and grain-shape analyses of debris-flow sources and deposits,and examination of remote sensing images.These efforts aimed to analyze the disaster process,influencing factors,and future prevention and control measures.The erosion,accumulation thickness,and spatial distribution characteristics of the debris-flow gully indicated that the provenance area is mainly concentrated in the tributary source on the right bank upstream of Caotan Village.Abundant fine sand materials in this provenance area and traditional irrigation methods created favorable conditions for slumps to occur under strong seismic motions.Field investigations revealed that the source material was mainly supplied by numerous shallow(2-3 m)slumps,which gradually broke apart and dispersed during the migration process.The presence of a shallow stable aquiclude and exposed spring water provided a continuous water supply for the materials in the provenance area,ultimately forming a mobile debris flow.Before the disaster,both longitudinal and transverse profiles of the gully in the circulation area were complex,with some small ponds and ditches being blocked,which increased the paroxysmal and destructive ability of debris flow.The spatial distribution characteristics of residual debris and mud traces showed that the debris flow demonstrated characteristics of typical plug flow and high viscosity.The increasing potential energy eventually led to debris flow breaking through valley barriers and continuing to flow.Erosion and accumulation coexisted along the way,reshaping the debris-flow valley.The topography of the accumulation area further opened,causing the debris flows to further disperse and accumulate.Houses located in the valley of the accumulation area were the most seriously affected.In addition,severe cold weather,the midnight timing of the earthquake,and a lack of public awareness about the nature of such disasters aggravated the severity of the debris flow to a certain extent.The upper reaches of the Yellow River contain many small-and medium-sized basins with similar stratigraphic structures,landforms,and hydrological conditions,as well as comparable human settlement environments and human-land relationships.Therefore,investigations should be carried out systematically based on the characteristics of this disaster.Regular inspections and investigations for the identified high-risk areas and hidden dangers should be conducted to strengthen the prediction and early warning of major disaster risks.Furthermore,public awareness campaigns should be strengthened to improve scientific understanding of earthquake-induced disasters.
作者
罗毅
李德文
姜文亮
李林林
焦其松
田云锋
李强
李永生
LUO Yi;LI Dewen;JIANG Wenliang;LI Linlin;JIAO Qisong;TIAN Yunfeng;LI Qiang;LI Yongsheng(National Institute of Natural Hazards,Ministry of Emergency Management,Beijing 100085,China;Key Laboratory of Emergency Satellite Engineering and Application,Ministry of Emergency Management,Beijing 100085,China;Key Laboratory of Compound and Chained Natural Hazards Dynamics,Ministry of Emergency Management,Beijing 100085,China)
出处
《地震工程学报》
CSCD
北大核心
2024年第4期802-817,共16页
China Earthquake Engineering Journal
基金
国家自然科学基金资助项目(42271017,42271015)
中央级公益性科研院所基本科研业务专项重点项目(ZDJ2019-14)
民用航天技术预先研究项目(D040405)。
关键词
积石山地震
地震滑塌
泥石流
高分7号
官亭盆地
Jishishan earthquake
earthquake-induced slump
debris flow
GF-7
Guanting Basin
