Active tectonic assessment around Rudbar Lorestan dam site, High Zagros Belt (SW of Iran)

Abstract

The aim of this study is to improve a method to develop an integrated quantitative geomorphic analysis of tectonic activity around the Rudbar Lorestan dam site and powerhouse in the High Zagros Belt (HZB), southwest Iran, using several tectonic geomorphic indexes including stream length–gradient index ( SL), drainage basin asymmetry ( Af), hypsometric integral ( Hi), ratio of valley floor width to valley height ( Vf), and transverse topographic symmetry factor ( T). Considering the results obtained from each of the above indexes, as combined and weighted by the “analytic hierarchy process” (AHP) and plotted on the “index map of relative active tectonics” ( Iat) by El Hamdouni et al. (2008), four classes are recognized in the study area; i.e. low, moderate, high, and very high, according to the rate of tectonic activity in the subbasins. Low to moderate intensities correspond to the northeast (along the Main Zagros Reverse Fault: MZRF) and southwest parts of the study area; whereas subbasins in the middle parts, along the Saravand–Baznavid strike-slip fault, are classified into high or very high intensities because of recent activity and the oblique-slip movement of the Saravand–Baznavid fault. The results show that the Rudbar Lorestan dam site and powerhouse are located in an active strike-slip fault zone and that a seismic hazard may occur along this zone in the future.