嘉黎断裂带东南段空间展布、变形特征与工程效应OA

[Objective]The Tibetan Plateau,as the world's largest and most tectonically active continental collision orogenic belt,has long been at the forefront of global geoscience research due to its complex tectonic patterns and ongoing dynamic processes.The Jiali Fault Zone along the southeastern margin of the Tibetan Plateau serves as the key structure for the southeastward extrusion of plateau materials.Its tectonic attributes,geometric distribution,and activity are of great significance for understanding the Cenozoic tectonic evolution of the plateau,the kinematics of southeastward extrusion of plateau materials,the genesis of regional earthquakes and geohazards,and the assessment of regional engineering risks.However,the precise spatial location and Holocene activity of the southeastern segment of this fault zone(from Guxiang to Gongrigabu)have long been subject to controversy due to rugged terrain and dense vegetation cover.[Methods]This study systematically investigated the spatial distribution,structural characteristics,and activity of the Jiali Fault in this critical,disputed segment by integrating multiple techniques,including high-resolution remote sensing image interpretation,field geological and geomorphological surveys,magnetotelluric sounding,and drilling data.Based on these investigations,we further analyzed the potential underground engineering effects triggered by fault activity.[Results and Conclusions](1)The southeastern segment of the Jiali Fault Zone extends continuously southeastward from south of Guxiang through Galongla and Jinzhunongba to Langqiunongba.Remote sensing interpretation reveales different kinds of structural geomorphologies including fault troughs,sag ponds,and push-up ridges.Field surveys identified bedrock fault planes and horizontal striations,demonstrating predominantly right-lateral strike-slip motion.Geophysical surveys revealed distinct low-resistivity fracture zones(approximately 200-300 m wide)in the Cuokanongba,Galongla,Jinzhunongba,and Langqiunongba areas,indicating that the Jiali Fault dips 60°-80° to the southwest.Drilling cores revealed significant fault fracture zones in the Galongla area.Together,these findings confirm the existence and NW-SE-trending distribution of the Jiali fault.In combination with evidence for Holocene activity in the western segment,offset of late Pleistocene-Holocene sedimentary profiles in the Gongrigabuqu segment,and new survey results,the southeastern segment of the Jiali Fault plausibly exhibits Holocene activity.(2)Activity along the Jiali Fault may trigger the following seven types of underground engineering effects and associated adverse geological issues:co-seismic displacement(with an estimated maximum displacement up to 5-6 meters),rock mass degradation,high stress and rockbursts,ground motion amplification,high-pressure water and mud outbursts,localized geothermal anomalies,and secondary hazards at tunnel entrances.These effects form a complex and intrinsically linked geological risk chain,posing significant challenges for deep,long tunnels crossing fault zones.Therefore,for underground projects crossing potentially active faults where avoidance is impossible or cost-prohibitive,we recommend implementing systematic reinforcement designs and risk control measures corresponding to these effects across the entire project life cycle,starting from the planning and site selection stages.[Significance]This study addressed the challenges of applying traditional active detection methods to complex geological environments,such as high topographic relief,deep vegetation cover,and the absence of fine-grained Quaternary deposits,along the southeastern margin of the Tibetan Plateau.This study focused on remote sensing interpretation,high-precision geophysical surveys,and cross-fault drilling,thereby establishing a successful model for future active fault exploration in similar regions.The outcomes not only provide critical geological constraints for refining the tectonic model of the southeastern Tibetan Plateau,but also offer an indispensable scientific basis for planning,seismic design,and risk prevention of major engineering projects crossing active fault zones.Furthermore,the research methodology establishes a successful model for future active fault investigations in comparable regions.