QUANTITATIVE ANALYSIS OF RELATIVE TECTONIC ACTIVITY USING GEOGRAPHIC INFORMATION SYSTEMS(GIS) IN THE MEYMAND AREA,CENTRAL ZAGROS,IRAN

Neotectonics is a major factor for controlling land form development in regions with active tectonics. The study records evidences of neotectonics activities in the south east of the Zagros mountain range that found to be responsible for the present-day geomorphic set-up of the area in the late Certaceous and strengthed during the early Miocene due to the collision of the Arabian and Eurasian plates. The area is located along the simply folded belt of the Zagros. To assess tectonic activities in the area we analyzed geomorphic indices: The stream length-gradient index(SL), Drainage basin asymmetry(Af), Hypsometric Integral(Hi), Valley floor width-valley height ratio(Vf), Drainage basin shape(Bs). Geomorphic indices indicate the presence of differential uplifting in the geological past. These indices were combined to yield the relative active tectonics index(Iat) using geographic information systems(GIS). Based on Iat values, the study area was divided into four parts: Class 1 (very high relative tectonic activity,4.3% in the area); Class 2 (high, 26.7%); Class 3 (moderate, 40.5%); Class 4 (low, 28.5%). Subcatchments of the basin indicates different directions of stream migration depending on their flow direction in the area. There are neither lithologic controls nor localized climate that causes the asymmetry, so it seems reasonable for the stream migration that tectonics can account. The results are consistent with field observations on landforms and geology.