Active tectonic analysis of Atrak river subbasin located in NE Iran (East Alborz)

Study of tectonic affects in many fluvial systems shows that, rivers are valuable tools to active tectonics surveying. Study of stream channels and their associated deposits offset by faulting may reveal the amount displacement at particular site and give information that is critical for future earthquake hazards evaluation. Study area which is a subbasin of Atrak river is located at the NE Iran (East Alborz) and west of Bojnurd city. Aim of this research is separating high tectonic activity areas from low tectonic activity areas. In this research, in order to evaluate rate of tectonic activity the drainage basin asymmetry factor (Af), Transverse topographic symmetry factor (T), hypsometric integral (Hi) hypsometric curve (Hc), stream–gradient index (SL), valley ?oor width–valley height ratio (Vf) and Relative tectonic activity (Iat) were calculated. Based on Iat values, the study area was divided into four parts: Class 1 (very high relative tectonic activity: subbasin 2 and 3), class 2 (high relative tectonic activity: subbasin 4), class 3 (moderate relative tectonic activity: subbasin 5), class 4 (low relative tectonic activity: subbasin 1). Results of this research show that northern side of Qharajeh basin is inactive part of study area and southern side of Qharajeh basin is actives part.