Lajia Ruins in Qinghai Province Might Be Caused by Seismic-induced Liquefaction Mudflows of Sands and Soils:Implication from the Jishishan Earthquake in Gansu Province on December 18,2023
The Lajia Ruins,often called the"Pompeii in the East",situated in Minhe County,Qinghai Prov-ince,is well known as an archaeological site documenting a catastrophic event approximately 3,900 years ago.The causation of the disasters responsible for the destruction of the Lajia settlement has been in hot debate for an extended period.Various points of view regarding"flooding causes"has been gained acceptance within the gen-eral public.However,is the catastrophic event indeed linked to flooding?The 6.2-magnitude earthquake struck in Jishishan County,Gansu Province on December 18,2023,with its epicenter located a mere 16 kilometers from the Lajia Ruins.This seismic event not only substantially damaged the Lajia Ruins Museum but also trig-gered mudflows in Jintian Village and Caotan Village,Zhongchuan Town,Minhe County,just 5 kilometers away from the Lajia Ruins.This catastrophic event led to the direct burial of residential structures and villagers,po-tentially representing a replication of the formative processes that gave rise to the Lajia Ruins.Consequently,it emerges as a pivotal empirical material for comparative studies investigating the causative factors underlying the genesis of the Lajia Ruins.Through conducting field investigations and comprehensive studies of the seismic dis-aster,it is conceivable that contemporary insights may shed light on the longstanding enigma surrounding the genesis of the Lajia Ruins.The earthquake has induced an upward surge of groundwater from the ancient river-bed gravel layers beneath the loess,causing the liquefaction of the loess and the rapid downstream flow of mud through gullies.As the mudflow encountered obstacles when passing through Caotan Village and Jintian Village,it overflowed the gullies,destroying some houses and even burying villagers.The distinctive geological stratigra-phy and the abundance of groundwater,triggered by seismic activities,resulted in soil's liquefaction and mudflows'formation,constituting crucial factors in the genesis of seismic disasters in Zhongchuan Town.Field investigations indicated the tragic burial of a family of five in Caotan Village was not the result of a typical"sand surge",nor does it exhibit traces of"flooding".Instead,it is attributed to secondary seismic hazards,specific-ally mudflows induced by the earthquake.Combined with the preservation status of cultural remains and sedi-mentary characteristics at the Lajia Ruins,inference suggests that the ancient earthquake 3,900 years ago,along with the resultant liquefaction of soil and the rapid flow of mud,provides a plausible explanation and reconstruc-tion for the instantaneous catastrophe at the Lajia Ruins.The formation of the Lajia Ruins is likely unrelated to the mountainous flash floods induced by heavy rainfall and certainly not caused by the purported megaflood.
Lajia RuinsJishishan Earthquakeliquefied mudflowinstantaneous catastrophenorthern mar-gin of Lajishan Mountain FaultYellow River
李俊磊、张绪教、鱼海麟、王一凡、张向格、李秋蓉、李彩虹、张丽蕾
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中国地质大学(北京)地球科学与资源学院,北京 100083
中国地质大学(北京)陆内火山与地震教育部重点实验室,北京 100083
中国建筑材料工业地质勘查中心青海总队,青海西宁 810008
School of Geography,Earth and Environmental Sciences,University of Plymouth,Plymouth PL4 8AA,United Kingdom
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