River Parttern Anomalies Along Zhengzhou-Jinan Segment Of Yellow River,North Of China,and Its Relationship With Subtle Fault Activity

Many seismogenic faults,located within basin or plain with thick Quaternary alluvium,are characterized by subtle activities.The traditional detection methods,relied on the yourgest faulted strata by earthquake rupture,is not always suitable for accurate judging of latest active nature and age of fault.Using alluvial river sensitivity to surface deformation to evaluate fault activity is a potential for study of activity of subtle faults.The identification of river pattern anomalies by 3S technology can provide qualitative and quantitative basis for the study of spatial distribution and properties of active faults.The study is focused on the Zhengzhou-Jinan segment of Lower Yellow River.Based on remote sensing images from 1990 to 2013,we extracted the geometric characteristics of the surface water area in several periods,segmented the river,and calculated the river sinuosity for 6 years and the water surface overlap rate for 5 periods.This article mainly obtains the following understandings:1.The mean value of the centerline curvature of the target river section(six periods)varies greatly along the way;many abnormally high values are in good agreement with the spatial distribution of the faults near the Yellow River,and canbe explained by the inherited activities of the subtle faults;The adjustment of the water level of the canal cross the Yellow River also has an important influence on the curvature of adjacent river sections.2.On the whole,the mean overlap ratio of multiple periods increases gradually from upstream to downstream,it reflects the evolution trend of river morphology from the upstream with large width-to-depth ratio and local braided flow to a meander with a small width-to-depth ratio downstream.On a smaller scale,the abnormally low overlap ratio reflects local channel instability,which can be explained by the hidden tectonic activity and surface deformation trend obtained from curvature analysis.3.The surface deformation characteristics indicated by the river pattern anomaly,which indicate that the faults near,or cross,Zhengzhou-Jinan section of the Yellow River still show the active characteristics.4.There are some differences in river pattern characteristics in different periods,it is mainly related to the sand and water regulation behavior of the Xiaolangdi Hydropower Project.However,the multi-period mean value of relevant river pattern indexes can still reflect the river pattern anomaly caused by local surface deformation,and can be used for the analysis and evaluation of subtle tectonic activity and river reach stability.This study show that the mean value of the relevant parameters can reflect abnormal river morphology caused by local factors.This not only provides an independent interpretation and evaluation basis for understanding and evaluating the activity and seismic hazard of adjacent Yellow River faults,but also provides new technique for analyzing the activity of subtle faults and the stability of river sections using abnormal features of river morphology.