LAUSR

Abstract The geometry of river networks is particularly sensitive to active tectonic deformation. Morphotectonic analyses conducted using geomorphic indices and numerical models are useful methods with which to identify such deformation. The northeastern (NE) margin of the Tibetan Plateau is characterized by active tectonics, easily erodible bedrock and well-developed valleys, and is thus an ideal region for studying the effects of tectonics on the landscape evolution. Here we firstly identify the systemic asymmetrical valleys in the Maxianshan area, NE Tibetan Plateau. To quantitatively analyze the asymmetrical characteristics of these valleys identified in the southern Maxianshan, 33 parallel streams were investigated by using two drainage basin analytical techniques, namely, the transverse topographic symmetry factor (T) and asymmetry factor (AF). Our results show that the mean T value is 0.14 (magnitude) and 319.08° (direction) and the majority of the AF results are