Liquefaction Flowslide and Damage Characteristics of Buildings in Zhongchuan Town Triggered by the Jishishan Earthquake
On December 18,2023,at 23:59,an Ms6.2 earthquake struck Jishishan County,Linxia Prefecture,Gansu Province,China.At 20 kilomiter from the epicenter,this earthquake triggered a chain of landslide-mudflow in the neighboring Caotan and Jintian Villages of Zhongchuan Town,in Minhe County of Qinghai Province,resulting in 20 fatalities,19 roads blocked,and 65 residential buildings destroyed and buried.A team of scientists was promptly assembled and dispatched to the earthquake-affected areas immediately following the tremor.Utilizing Unmanned Aerial Vehicle(UAV)photogrammetry,comprehensive field surveys,and rigorous on-site sampling,the team investigated the underlying causes of the earthquake-induced landslide-mudflow.Additionally,65 samples of building damages were meticulously collected and analyzed to determine the specific patterns of destruction inflicted by the mudflow.(1)This secondary geological disaster exemplified a complete chain disaster process:earthquake-liquefaction-landslide-mudflow,featuring a characteristic gully-type viscous mudflow.The primary source of this mudflow stemed from the liquefied sandy loess within the sliding source area.(2)The liquefaction of saturated loess triggered by the earthquake served as the primary catalyst for the landslide-mudflow.The interaction of strong seismic shaking,saturated loess conditions,and gully topography created an ideal setting for this geohazard.Furthermore,factors such as land reclamation,farmland irrigation,and low-temperature freezing elevated groundwater levels and saturate the lower soil layers,heightening the likelihood of loess liquefaction.It was possible that static liquefaction-induced landslides might kept in the aftermath of the earthquake,potentially leading to a continued expansion of the affected landslide-mudflow area.(3)The dynamic impact of the landslide-mudflow on buildings was primarily manifested through both impact and silting,with silting being the dominant factor.The closer a building was situated to the main flowslide line,the more severe the damage it was likely to incur.Therefore,it is recommended that new buildings in this region adopt brick-concrete or frame structures,which offer shorter self-seismic periods and superior structural integrity.These findings provide insights into the formation mechanisms and prevention strategies for similar secondary chain geological disasters induced by earthquakes.
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