Process and causes of the debris flow in Zhongchuan Township induced by Jishishan Ms6.2 earthquake in 2023
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 Ms6.2 earth-quake in 2023,has attracted significant attention owing to its high casualty rate.A comprehensive inves-tigation 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 nat-ural 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 fu-ture prevention and control measures.The erosion,accumulation thickness,and spatial distribution char-acteristics of the debris-flow gully indicated that the provenance area is mainly concentrated in the tribu-tary source on the right bank upstream of Caotan Village.Abundant fine sand materials in this prove-nance 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 nu-merous 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 dis-aster,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 accumu-lation 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 ag-gravated 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.There-fore,investigations should be carried out systematically based on the characteristics of this disaster.Reg-ular inspections and investigations for the identified high-risk areas and hidden dangers should be conduc-ted 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.
万方数据
维普
