Responses of Stream Geomorphic Indices to Piedmont Fault Activity in the Daqingshan Area of China

A recent correlation of stream geomorphic indices to fault activity has revealed that stream geomorphologies in bedrock mountain areas are good records of local fault movements. The Daqingshan piedmont fault is one of the main active faults in the fault system on the northern margin of the Hetao Basin and has produced frequent large-scale earthquakes since the Late Pleistocene. In the present study,following the segmentation regime of previous studies,we divide the fault zone into five segments,namely,the Baotou,Tuyouqi West,Tuzuoqi West,Bikeqi,and Hohhot segments,and we discuss the relationship between the drainage basin geomorphology and the piedmont fault activity in the Daqingshan area using 30 m spatial resolution Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) data. We use a range of geomorphic indices to examine the drainage basins in the Daqingshan area,including the channel steepness index (ksn),slope,hypsometric integral (HI),relief degree of land surface (RDLS),and stream lengthgradient index (SL),extracted with ArcGIS and MATLAB,and we also consider local lithologic and climate aspects. Furthermore,we compare the geomorphic indices with the slip rates of individual segments of the Daqingshan piedmont fault and paleoseismic data. The results show that the geomorphic indices of drainage basins in the Daqingshan area are primarily affected by the piedmont fault activity in the Daqingshan area. The geomorphic indices also demonstrate that piedmont fault activity has been the most intense in the middle segment of this fault system since the Late Quaternary and decreases towards the two sides.