Responses of Stream Geomorphic Indices to Piedmont Fault Activity in the Northern Segment of the Red River Fault Zone

Abstract

Based on a digital elevation model (DEM) and GIS technology, we extracted and analyzed stream geomorphic indices—such as the slope, relief degree of the land surface (RDLS), hypsometric integral (HI) and channel steepness index (ksn)—of the Cangshan Piedmont Fault, Fengyi–Dingxiling Fault and Midu Basin Margin Fault in the northern segment of the Red River Fault Zone. This work indicates that all the stream geomorphic indices show higher values, with the highest values along the Cangshan Piedmont Fault, followed by the Fengyi–Dingxiling Fault, and the lowest values along the Midu Basin Margin Fault, forming a decreasing trend from north to south. Based on lithology, climate and tectonics, we infer that neotectonic activity is the main factor controlling the development of the drainage geomorphology. The results show that the northern segment of the Red River Fault Zone is highly active and that the activity level shows a decreasing trend from north to south. The results of this study are consistent with previous conclusions that the overall activity of the Red River Fault Zone weakens from north to south, and the activity in the northern segment has been the most intense since the Late Pleistocene.