阿尔金断裂中段南侧白干湖断裂遥感影像特征及地震危险性OA

[Objective]Accurately delineating the spatial distribution and geometric scale of active faults is essential for understanding crustal deformation and assessing regional seismic hazards.While the Altyn Tagh Fault(ATF)has been extensively studied,its adjacent secondary structures—such as the Baiganhu Fault—remain poorly constrained regarding their geometry,slip history,and seismic potential.This study aims to systematically characterize the offset geomorphology of the Baiganhu Fault,establish its segmentation,and evaluate its potential for generating large earthquakes,including multi-fault cascading ruptures with the ATF.[Methods]Using multi-source high-resolution satellite imagery and digital topographic data,we conducted detailed geomorphic mapping of the Baiganhu Fault.Displaced landforms(e.g.,offset gullies,alluvial fans,pressure ridges,and sag ponds)were measured.We constrained displacement variations at individual measurement points using Gaussian cumulative probability density(COPD)distributions to interpret the displacement accumulation pattern and evaluate coseismic slip.[Results]The Baiganhu Fault extends for approximately 247 km along a general northeast-east(NEE)strike,displaying prominent left-lateral strike-slip geomorphic features.Based on fault geometry and deformation patterns,it is divided into western,central,and eastern segments.The central segment hosts a well-preserved～50-km-long surface rupture zone with an average coseismic displacement of 4.8 m.Statistical analysis of 99 offset gullies yields an average horizontal offset of 4.3-4.8 m for the most recent event,corresponding to a moment magnitude of MW 7.4±0.3.A full-segment rupture could generate an earthquake of MW 7.8±0.3.Furthermore,the～5-km-wide stepover separating the Baiganhu Fault from the main strand of the ATF is unlikely to act as a permanent barrier,making a cascading rupture mechanically plausible.[Conclusions]The Baiganhu Fault is a highly active left-lateral structure capable of generating MW 7.4 events.Regional seismic hazard models must incorporate the scenario of cascading ruptures between the Baiganhu Fault and the Altyn Tagh Fault to avoid underestimating seismic risk to surrounding infrastructure.[Significance]This study provides critical quantitative constraints on the geometry,slip behavior,and seismic potential of a previously under-studied secondary structure within the ATF system.By highlighting the potential for multi-fault cascading ruptures,our findings underscore the need to update regional seismic hazard models,which is vital for risk mitigation and infrastructure safety in the region.