DEM and GIS analysis of the stream gradient index for evaluating effects of active tectonics: Tula basin, north Tibet, China

Geomorphic indexes and drainage pattern analysis have been widely used as proxies to detect active tectonics and surface processes in recent years. In this study, we use the stream length-gradient index to detect active tectonics in the intraplate Tula basin, bordered by the active left-lateral strike-slip Altyn Tagh fault to the north and Kunlun fault systems to the south. The normalized stream length index along stream show that the joinpoint region of the East Kunlun Fault system and the Altyn Tagh Fault appears to be highly active currently whereas the tectonic activity decreases gradually away from the joinpoint. The high normalized stream length values are of potential risky for the strong earthquakes along the Altyn Tagh Fault in future. In addition, comparing with stream length-gradient index, the normalized stream length-gradient index supplies better results with anomalies and more suitably reflects the main tectonic of the study area.