The coupling effect of coseismic landslide-mudflow disaster chain induced by Jishishan strong earthquake in Gansu Province
In recent years,typical landslide-mudflow disaster chain events induced by strong earthquakes and ex-treme weather in loess areas have become more frequent. Compared with single disasters,chain geological disas-ters have stronger concealment,wider spread,higher damage degree and more serious losses. Therefore,the re-search on the prevention and control of chain geological disasters has always been a hot and difficult point in di-saster prevention and reduction. At 23:59 on December 18,2023,an Ms 6.2 magnitude earthquake struck Jish-ishan County,Linxia Prefecture,Gansu province,at a depth of 10 km,killing 151 people. The strong earth-quake triggered a landslide-mudflow chain disaster in Caotan Village and Jintian Village,Zhongchuan Town,Minhe County,Qinghai Province,resulting in a total of 20 deaths,the disaster chain fatality rate accounted for 13.5％ of the total number of earthquake fatalities. After the disaster,a comprehensive and systematic study on the landslide-mudflow disaster chain was carried out by means of remote sensing image processing and interpreta-tion,literature sorting and screening,UAV photographic aerial survey,detailed field survey and visit,and on-site sampling and analysis testing,so as to recover and reappear the start-slide-flow-accumulation process of the landslide-mudflow disaster chain. This paper discusses and puts forward nine major coupling and disaster-caus-ing effects such as surface freezing blocking water retention in the slip source area,gully leveling backfill water retention in the slip source area,platform irrigation seepage filling effect in the slip source area,vibration lique-faction screening effect in the slip source area,growth rate of the funnel closure in the slip source area,soil dif-ferential flow sorting effect in the flow area,collapse recharge effect in the flow area,acceleration effect of ice filling water at the bottom of the flow area,and upstream seepage recharge and range extension effect in the accu-mulation area. The Zhongchuan landslide-mudflow chain disaster caused by the Ms 6.2 earthquake in Jishishan,Gansu Province is a typical secondary geological disaster of the same earthquake,which is transformed into a di-saster by the coupling and superposition of multiple disasters such as earthquake,landslide and mudflow,and its impact and effect are much greater than that of a single disaster,and it has the comprehensive characteristics of suddenness,high speed,concealment,confusion,destruction and remoteness. The Zhongchuan coseismic land-slide-mudflow chain disaster with nine linkage coupling disaster-causing effects is obviously different from the traditional geological disasters such as landslides and debris flows,and the transformation of disasters and disas-ter-causing factors are complex and unique. In the process of promoting the construction of beautiful villages and the Belt and Road,the relevant land use development and engineering construction planning must fully consider the risks of regional landslides,debris flows,mountain floods and their coupling disasters,scientifically and ra-tionally lay out land and engineering planning and design,ensure the flooding and silting of valleys,and reserve safe transition areas,so as to prevent disasters and avoid damage to the greatest extent. Long-term and large-scale agricultural irrigation is the most important source of recharge for the loess layer with large thickness and high water content to saturation in the gentle slope area of the high terraces of the Yellow River,and chain disas-ters occur under the action of strong earthquakes. Therefore,under the condition of ensuring water for agricultur-al production,strengthening the drainage of the slope zone in the irrigation area,optimizing the irrigation meth-od,and lowering the groundwater level are effective measures to prevent the occurrence of similar landslides and chain disasters and ensure the safety of the geological environment in the loess gentle slope plateau area. The research can provide a scientific reference for the formation mechanism and prevention and control of chain geological hazards.
Jishishan earthquakelandslide-mudflow disaster chainlinkage couplingupper reaches of the Yellow Rivernortheastern edge of the Tibetan Plateau
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