Response of the stream geomorphic index to fault activity in the Qujiang fault on the southeastern margin of the Qinghai-Xizang Plateau

Based on 12.5 m resolution ALOS_PALSAR DEM data and hydrology analysis tool in Arcgis10.6, the stream geomorphic indices such as slope, relief degree of the land surface (RDLS), hypsometric integral (HI) and stream length gradient (SL) along the Qujiang fault (QJF) were extracted to analyze the impact of several stream geomorphic indices on the QJF’s tectonic activity. Previous studies divided the Qujiang fault into three segments: northwest (NW), middle, and southeast (SE), from which fluvial geomorphic indices were extracted. The average HI value of the NW segment is 0.34, and the average SL value is 334; the average HI value of the middle segment is 0.44, and the average SL value is 383; and the average HI value of the SE segment is 0.45, and the average SL value is 415. The results indicate that the middle and SE segments are more active than the NW segment. Through the comprehensive analysis of lithology, climate and tectonic activity in the QJF region, it is believed that tectonic activity is the primary factor influencing the development of stream geomorphology. Field investigations of typical landforms and outcrops were conducted to analyze the historical seismicity of the QJF and the geometry of the fault, and the results showed that the middle and SE segments are more seismically active than the NW segment. The results of the stream geomorphic indices in this paper are consistent with previous studies, indicating that the seismic hazard in the QJF’s middle and SE segment requires further investigation.