New insights into the effect of the quaternary fault activity on river knickpoints in the Central Alborz (Iran)

This study examines the knickpoints in a region to provide new insights for assessing the Tectonically Formed Knickpoints (TFKs). In this paper, we have used a quantitative method to recognize TFKs using two different river steepness methods; the stream gradient (Gd) and the normalized steepness index (kSn). Analysis of the extracted TFKs with the longitudinal profile, logarithm slope-area plots, and natural logarithm gradient-distance plots suggests that these knickpoints correlate with the active segments of faults. In addition, evaluation of the TFKs indicates that the different length and height of the TFKs can be related to the different features of each fault. The investigation of TFKs was implemented in the Central Alborz located at the southern margin of the Caspian Basin in northern Iran which is a part of an active deformation region of the Arabian and Eurasian plate collision zone. The investigation of TFKs suggests that the Quaternary faults' activities are related to the recent tectonic activity in the northern flank of the Central Alborz as well as the central part of the Central Alborz which is consistent with Global Positioning System (GPS) studies and increased uplift rate. The results are in agreement with field observations in terms of geomorphic features and geology.