Evaluation of active tectonics using analysis of morphometric and geomorphic parameters (Case study: West Kerend river basin)

Active tectonics is defined as neotectonic movements that are likely to occur in the future and threaten human societies (Burbank et al, 2001). Active tectonic studies are important topics in the earth sciences and their results are widely used to assess natural hazards and land use development and management programs in densely populated areas (Pedrera et al, 2009).  Hisami et al (2006) estimates shortening of the northwestern Zagros to a maximum of 5 mm per year, and Mirzaei (1997) estimates that more than 50% of the recorded earthquakes in Iran occur in the Zagros Zone and is the most seismic-prone area in Iran. Shabani (2004) has identified the Kandand fault as an earthquake source in Kermanshah province. The west of the Kerend Basin is in the folded Zagros Zone and the Kereend seismic fault is located in this basin. Therefore, it seems that tectonics of the region is active and considering the location of the city of West Kereend and many villages and human settlements in the basin, evaluation and estimation of its active tectonics are necessary. The purpose of this study was to evaluate and estimate the active tectonics of the Kereend West basin using drainage network analysis.

The data of this research include (30 meters) ASTER DEM, geological map 1: 100000, topographic maps 1: 50000. Then, during field visits, the geomorphological features of the West Kerend basin were examined. Then, using the DEM of the area, the area of West Kerend basin and its drainage network were extracted and the waterways were ranked according to the Straler method. Then the geometric features, drainage network and topography of the West Kereend basin were calculated. Then, linear morphometric, shape and uneven morphometric parameters (Table 1) and geomorphic indices for this basin were calculated. The values of morphometric and geomorphic parameters are classified according to Table (2) and have scores of 1, 2 and 3, which indicate low, medium and high tectonic activity, respectively. The classification of the amount of technical activity in the West Kereend Basin is based on the CR index. This index is the sum of the scores of morphometric and geomorphic parameters used (Table 3) and its high values indicate the most active tectonic conditions (Shukla et al, 2014).

The results of two linear morphometric parameters indicate the location of the West Kereend basin at the end of the youth stage of the erosion cycle and the anomaly of the drainage network and the low impact of these indicators on lithological conditions. The results of the shape parameter indicate the high roughness and elongation of the shape of the West Kereend basin due to tectonic uplift of the anticlines of the studied basin. Based on the values obtained from three morphometric parameters, the roughness of the West Kereend basin has moderate tectonic activity. The results of geomorphic indices also indicate the tectonic activity of the West Kereend basin. The value of index (Af) in the West Kereend basin indicates active tectonics and increase on the left side of the West Kereend River, which is due to the uplift of the Kereend Anticline due to the shortening of the Zagros and the Kereend drift movement on its southern edge. The index (T) of West Kereend basin also indicates the topographic asymmetry of this basin and indicates active tectonic intervention and the elevation of the left bank of the river. Based on the results of CR index, West Kereend basin is in the class with high tectonic activity.

The results of linear morphometric parameters indicate the location of the western Kereend basin at the end of the youth stage of the erosion cycle. The values of the shape parameter indicate the elongation of the basin and the elevation of the anticlines of the studied basin and the results of the morphometric parameters of the roughness also indicate the relative roughness of the West Kereend basin. The results of geomorphic indices also indicate the asymmetry of the basin and the existence of active formation on the left side of the river in the West Kereend basin. The results of CR parameter show that West Kereend basin is in the class with high tectonic activity. In general, the active tectonic status of the West Kereend basin includes active tectonics and the general uplift of the basin due to the shortening of the Zagros zone due to the Arabian plate pressure and the asymmetry of the basin and the uplift of the left bank of the river due to the westbound drift activity. This is consistent with the results of studies by Blank et al. (2003), Bachmanov (2003), and Hesami et al. (2006), who believe in the uplift of the northwestern Zagros. The tectonic activity of the Kereend West basin as well as the entire northwest Zagros range can cause active tectonic hazards such as earthquakes.