Assessing morphotectonic activity of coastal catchments in the Talesh geomorphology unit (Iran and Azerbaijan) using morphometric indice

Field methods and the use of seismic tools to determine tectonic activities in an extensive area is costly. Hence, the use of alternative methods including geomorphic indicators to determine and detect tectonic activities can be very beneficial. Many geomorphic indicators such as triangular surfaces, the surface leveling of the mountain front, the concavity of river profiles, pattern and drainage density, river longitudinal gradient, the ratio of the width of the valley to the height of the valley, the asymmetry of drainage basin, sinuosity of the mountain front, integral to the hypsometric, are used by researchers to determine tectonic activities and tectonic changes. The Talesh coastal basin is among the regions which are subject to extreme tectonic transformations due to the presence of numerous faults. Therefore, determination of tectonic activities of these basins are very important. The aim of this study was to evaluate the active tectonics, based on Morphotectonic and morphometry studies of catchment in the studied area. 

The study area of the Talesh Coastal unit, which stretches from the Sefidrud Valley to the Lankaran Basin in the Republic of Azerbaijan, extends from longitude 48° 22 ̋ 46 ̋ to 49° 23 ̋ 21 ̋ in east and latitude ° 51 ̋ 25 ̋ to 38° 51 ̋ 25 ̋ in the north.To achieve the objectives of this study, Alos-Polsar digital elevation model and HEC-GeoHMS software were used to extract 37 Basin and drainage networks and rivers of the studied area. Using morphometric indices, the calculation and analysis of the region’s morphotectonic were performed in 10.2 ARCGIS and Saga 2.1.2 Software. These indices include: the ratio of the width of the valley to the depth of the valley (VF), the ratio of Basin (Bs), asymmetry index of waterways (AF), the curve of the Hypmetric and Integral (Hi), River sinuosity Index (S) and Topography symmetry index (T). In order to evaluate and classify basins according to tectonic activity, the relative evaluation index of tectonic activities (IAT) was used in this study and the obtained results were validated with seismic data

Between the 37 sub-basins, 14 basins with an area of 2059 km2 (40.7% of study area) has high tectonic activity, 22 catchments with an area of 2979 (58.5 of study area) and has moderate activity and only one basin low activity. The overlap of the seismic data with the results of this study shows a good correlation with the fact that despite the low area of high tectonic activity basins (2059 km2 and 40.7% of the study area) about 71% of the large 2 seismic data were recorded.

The results of this study show that despite the exposure of multiple faults in this area, only 38% of the catchments are located in the field of active classification and other basins are between moderate to low tectonic activity. According to the IAT index, the most tectonic activity in Talesh basins in Iran are Chalasi and Emerald basins and Warcharand and Lankaran in the Republic of Azerbaijan. Overlap of seismic data with the results obtained from this research, show a good correlation.