Quantitative Geomorphic Indices Characteristics And Tectonics Of The Yong River Basin In Siming Mountain,eastern Zhejiang

There is a relatively complete ancient planation surface in the Simingshan area of eastern Zhejiang Province,found in 2006.Considered to be the widest low-altitude elevation planation surface in the eastern coast of China.The formation and evolution of ancient planation surface are based on geological structure,The discovery of the ancient planation surface of Siming Mountain promoted the study of regional tectonics(especially neotectonics)in the eastern China.Neotectonics activities directly affect the development of rivers(water systems),by quantitative analysis of the geomorphology of the river can reveal features of the neotectonics movement in the region.At present,research of the ancient planation surface of Siming Mountain geomorphological features and neotectonics is still in the exploratory stage,most of them are based on macro studies and need to be further studied.The Siming Mountain near South-North trend,dividing the mountain into two major river systems,the eastern part is the Yong River system,and the west is the Cao'e River system.There are two tributaries of the Yong River originated from Siming Mountain:the Yao River in the north and the Fenghua River in the south.Study on geomorphological indicators of Yong River basin,contribute to analyze the spatial differences in neotectonics uplift in the area,it also provides a theoretical basis for the evolution of the topography of the Siming Mountain and the tectonic deformation of the ancient planation surface.And the Yong River is located at the junction of deep faults in eastern China,affected by multiple fault zones,it has strong tectonic activity and earthquake,for the relationship of geomorphological parameters between macroscopic and microscopic,multi-indicator revealing geomorphological features,and basin-level relative tectonic activity assessment and other issues,provides the ideal place.Based on this,the paper mainly uses DEM as basic data,study on the evolution of Yong River Basin through geomorphological measurements,through the geomorphological parameters,such as Hypsometric Integral(HI)and Hypsometric Curve(HC),longitudinal profile fitting function,SL index(SL),and Hack profile,combined with the geological structure of the basin and the physical and geographical conditions,analyzed the characteristics of geomorphological evolution of Yong River basin,by studying drainage basin shape index(BS),drainage basin asymmetry(AF),mountain-front sinuosity(SMF),valley floor height-to-width ration(VF),and so on.Comprehensive analysis of the tectonic activities in the Yong River basin,and combined with geological structure data,carrying out comparative study of different catchment Yong River,exploring the differences in active structures in Simingshan area,comparing and verifying with the historical seismic data of the basin.(1)The results of Hypsometric Integral are not affected by the resolution of DEM data.However,affected by the area threshold,the optimal area thresholds for different watersheds are not exactly the same.Therefore,this paper divides 65sub-basins into a standard area of 32km~2.The results show that the Yong River Basin as a whole is in the prime period of geomorphological evolution and the transition from the prime to the old age,no infancy period,the HC curve is mainly concave.Spatial distribution of HI values affected by fault zones in the basin,the Yong River basin is consistent with the trend of major fault zones in the basin.(2)Comparison of geomorphological parameters,such as HI value and HC curve,maximum height,minimum elevation,relative elevation,and drainage area of Yao River and Fenghua River sub-watershed.Yao River basin HI value of 0.097,HC curve concave area larger amplitude,geomorphological evolution of old age into the whole stage.Fenghua River basin HI value of 0.286,HC curve concave to a lesser extent,Into the geomorphological evolution of the elderly(trend maturity)stage.Preliminary conclusions,the tectonic activity of the Fenghua River Basin was slightly stronger than that of the Yao River Basin,and the overall structural activity in the basin was more distinct.(3)According to the river longitudinal profile fitting results,the northerly tributary fitting function in Yao River basin is dominated by a logarithmic function,The fitting function of the southern tributaries of the Yao River basin is dominated by exponential functions.Longitudinal section fitting function of Fenghua River is more complicated,shows that the crust activity in the basin is significantly different.The longitudinal profile of the Yong River basin is mostly exponential and logarithmic,it is mainly a response to the uplifting tectonic movement in the region and the difference in lithology within the basin.(4)The paper selects longitudinal profile of 6 tributaries in the northern,central and southern parts of Siming Mountain for analyze Hack profile and SL index.The convex shape and tectonics of the Hack profile of the plateau in the upper and lower plates of the fault has good consistency.The Hack profile in the upper reach of the basin is more prone to convex than the downstream section,According to the response of tectonic activity to SL/K value and Hack profile in Simingshan area,southern mountainous tectonic activity is stronger than central and northern.(5)Through the extraction and grading of geomorphological parameters such as BS,AF,SMF,VF and HI of the Yong River sub-basin,calculate the arithmetic mean(S/n)of each parameter,quantitative assessment of the differences in relative tectonic activity in the Yong River basin.The regions with relatively strong tectonic activities are mainly distributed in the upstream tributaries of the Fenghua River Basin,the tributaries of the Yong River Basin,the Yao River tributaries on the northern margin of the Siming Mountain,and the lower reaches of the Yao River Basin.This is good consistency with the distribution of fault zones and seismic locations in the basin.