The role of the active tectonics in geomorphic anomalies of Gorgan Rud - Gharasu basin
Subject Areas :Agh- Atabai 1 , Nemati 2 , معصومه روستائی 3
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Keywords: Tectoni , Morphotectonic indices Gorgan Rud- Gharasu basin. ,
Abstract :
The study area is located in north of eastern Alborz range. In this study, it was evaluated the pattern of neotectonic in eastern Alborz and the distribution of seismicity and geomorphic pattern of Southern Golestan province. To assess tectonic activities in 22 separated subbasins, we have analysed neotectonic indices: the stream– gradient index (SL), drainage basin asymmetry (Af), reveres symmetry of topography (T), hypsometric integral (Hi), drainage basin shape (Bs) and mountain front sinuosity (Smf). The results of the analysis is accumulated and expressed as an index of relative active tectonics (Iat), which divided into four classes from relatively low to highest tectonic activity. The high class values of tectonic activity for Iat mainly occur in the south and southwest of the Gorganrud- Gharasu drainage basin, while the rest of the study area has classes of Iat suggesting moderate to low tectonic activity. The rate of tectonic activity in this area will increase from north to south. This increase can be related to the position of peaks steam gradient index along the faults and segment faults. Also value of drainage basin asymmetry is calculated for all of the subcatechments greater or less than 50 that shows tilt for each stream toward West or East. The results of this study show that the distribution of seismicity, geomorphic and tectonic movements of studied area has been affected especially by Khazar and North Alborz faults movement and thrust fault in north of Gorgan. Areas with high tectonic activity and the high measure of tilting indicate that there may be a thrust fault, with a NNE-SSW approximate trend. On the other hand, this seismicity trend may be related to a deep and relatively young thrust splay in north of the Alborz range front.
