雅砻江上游流域地貌特征及其构造响应分析OA

[Objective]The Upper Yalong River basin,situated on the southeastern margin of the Bayan Har block,is characterized by a well-developed river system.Large-scale NW-trending active faults traverse this drainage basin,where tectonic activity constrains regional fluvial geomorphic development and evolution.Current research has predominantly focused on fault activity,paleoseismic events,and seismic hazard assessment,whereas studies addressing basin-scale geomorphic characteristics and their response to tectonic deformation remain relatively limited.[Methods]Based on a 30-meter-resolution Copernicus Digital Elevation Model(DEM),98 sub-basins were identified within the Upper Yalong River basin.Five geomorphic indices were calculated for each sub-basin:hypsometric integral(HI),basin shape index(BS),asymmetry factor(AF),elongation ratio(Re),and mean normalized stream gradient index(SLKavg).These indices were quantified,classified,and integrated into a composite indicator—the relative strength of tectonic activity(Iat).Furthermore,the normalized channel steepness index(ksn)and knickpoints were incorporated to reveal the spatial differentiation of fluvial geomorphic characteristics and to explore the coupling relationship between tectonic activity and landscape evolution.[Results]In the Upper Yalong River basin,HI values range from 0.09 to 0.63.Some sub-basins are in an early stage of development and exhibit significant asymmetry.Left-lateral offsets of waterways,gullies,and alluvial fans are observed.SLKavg and ksn indicate strong tectonic uplift in most basins,accompanied by significant longitudinal variations in channel slope.Spatially,the Iat displays a pattern of alternating high and low values,with interconnected low-activity zones.Basins with low Iat values are distributed in linear belts along fault zones.Along the Wudaoliang-Changshagongma fault,which crosses the upper basin,Iat values are lower in the northern and southern Holocene-active segments.In contrast,the middle segment intersecting the Changshagongma Basin shows higher Iat values,possibly related to localized variations in tectonic deformation along fault segments.Basins traversed by the Ganzi-Yushu fault also exhibit relatively low Iat values,corresponding to strong activity at the block boundary.The geomorphic indices affect Iat in the order:Re>HI>AF>SLKavg>BS.[Conclusions]The strong consistency among tectonic activity,geomorphic features,and seismic activity in the study area directly reflects the role of tectonic processes in shaping the regional landscape pattern.The spatial differentiation of Iat and geomorphic indices effectively captures differential tectonic uplift and deformation along fault zones,providing clear geomorphic evidence of ongoing tectonic dynamics on the southeastern margin of the Bayan Har block.