ارزیابی تکتونیک فعال حوضۀ رودخانۀ کرند غرب با استفاده از تحلیل ویژگی‌های شبکۀ زهکشی

حوضه‌ آبخیز کرند غرب در شمال ‏غربی زون زاگرس چین‏خورده در غرب استان کرمانشاه واقع شده است. قرارگیری حوضه‌ مورد مطالعه در زون فعال زاگرس و وجود گسل کرند در محدوده‌ آن سبب فعال‏بودن حرکات تکتونیکی در این حوضه‌ آبخیز شده است. بنابراین، ارزیابی و برآورد تکتونیک فعال این حوضه و مخاطرات ناشی از آن لازم و ضروری است‏. هدف از پژوهش حاضر ارزیابی و برآورد تکتونیک فعال حوضه‌ کرند غرب براساس تحلیل ویژگی‏های شبکه‌ زهکشی است‏. بر این اساس، نخست محدوده‌ حوضه‌ مورد مطالعه و شبکه‌ ‏زهکشی آن استخراج شد. سپس، با استفاده از شاخص‏های مورفومتری و ژئومورفیک (‏da، ga، r، rb، rbd، af، t، bs، sl، و s)، که مختص تحلیل شبکه‌ زهکشی بوده، تکتونیک فعال حوضه‌ مورد مطالعه ارزیابی شد. در ادامه نتایج شاخص‏های مورفومتری و ژئومورفیک با هم مقایسه شد و با شواهد ژئومورفیک موجود در حوضه‌ کرند غرب تطبیق داده شد. نتایج حاصل از شاخص‏های مورد استفاده نشان می دهد ناهنجاری‏های سلسله‏مراتبی در شبکه‌ زهکشی حوضه‌ کرند غرب تحت تاثیر تکتونیک فعال است‏. این ناهنجاری به‏صورت تعداد بسیار زیاد آبراهه‏های رتبه‌ 1 مشخص شده است. نتایج شاخص‏های ژئومورفیک نیز بیانگر بالاآمدگی ساحل چپ رودخانه‌ اصلی به‏علت جنبش راندگی کرند بوده و این امر سبب کج‏شدگی حوضه و عدم تقارن شبکه‌ زهکشی در حوضه‌ مورد مطالعه شده است. یافته‏های پژوهش بیانگر آن است که ‏فعالیت‏های تکتونیکی در حوضه‌ کرند غرب به‏صورت بالاآمدگی کلی حوضه و نامتقارن‏بودن آن است‏. نتایج شاخص‏های مورفومتری و ژئومورفیک و تطبیق آن‏ها با شواهد ژئومورفولوژی تکتونیک فعال بیانگر فعال‏بودن تکتونیک در حوضه‌ کرند غرب است‏.

Assessment of active tectonics of the Karrand River Basin using drainage network feature analysis

Introduction : Tectonics in geology is the causative factor of buildings and the relationship between the geometrical form of the building and the effective forces (Purkerman Sedig; 2003, 38).Active tectonics also reflects the tectonic movements of the youngest period, the Quaternary, and in particular the Holocene and the present (Soleimani 1,1377 ). The Zagros Zone is tectonically active, and the ArabianOrsian plate convergence in the northwest Zagros is a combination of shortening and strikeslip strikeslip movements (Blank et al., 2003,401). (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 seismicprone 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 kerend 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 kerend West and many villages and human settlements in the basin, evaluation and estimation of its active tectonics is necessary. The purpose of this study was to evaluate and estimate the active tectonics of the Kerend West basin using drainage network analysis. Materials and Methods : This research is based on descriptiveanalytical, library, field, statistical, and geomorphic and morphometric indices. Research data include tenmeter DEM, 1: 100,000 geological map, and 1: 50,000 kerend topographic map, IRS satellite imagery, and Google Inheritance imagery.Also during field surveys and surveys of satellite and Google Earth imagery geomorphic evidence of active tectonics in the basin was identified.Then, using DEM of 10 m area, the area of the west of the Kerend basin and its drainage network were extracted and ranked using the Straler Waterway method.In this study, anomalies and morphometric indices were calculated, followed by morphometric indices of ga, R, Rb and Rbd and geomorphic indices of Af, T, Bs, SL and S (Table 1).The results of the geomorphic and morphometric indices are then compared with the geomorphic evidence and Based on the analysis of drainage network conditions and geological conditions, the active tectonic status in the west of Kandand basin is determined. Findings: waterway of 1 rank have the highest rate of anomalies in the kerend West basin and the number of Hat hierarchical anomalies in this basin is 730 waterways.This illustrates the impact of tectonic activity on the drainage network of the kerend Basin.The values of a and ga indices also indicate anomalies in the drainage network and tectonic activity of the studied basin. The values of Rbd and R parameters also indicate the hierarchical anomalies and the impact of the drainage network on the kerend Basin from tectonic activity. The index value (Af) in the west kerend basin indicates active and tectonics uplifit on the left of the kerend River, That is the direction of the northwestsoutheast river. The left fringe of the river is due to the uplift of the kerend anticline by the Zagros shortening and thekerend thrust movement in its southern flank.The index (T) of the west kerend basin reflects the topographic asymmetry of the basin.And indicates active tectonic interference and elevation of the left bank of the river.Indices (Bs) of the kerend Basin indicate that the uplift of the tectonicallyinduced mountain fronts is more active than the erosional processes and has stretched the form of the West kerend Basin.Indicator (S) of the kerend River indicates that the river is not in equilibrium due to active tectonics and is relatively straight.The index (SL) of the west of the kerend River reflects drastic changes in the river’s longitudinal profile due to active tectonics.The large number of lowranking waterways in the Kandrab West basin as a geomorphic evidence confirms the existence of anomalies in the drainage and tectonic network active in the basin and confirms the results of morphometric indices.The asymmetry of the watershed, the west of the river, and the drainage network and the longer length of the watercourses on the left of the river indicate the geomorphological evidence confirming the values of the AF and T indices. Result : The anomalies of the drainage network of the Kerend West Basin were evaluated by morphometric indices and their results indicate the existence of hierarchical anomalies in the drainage network of the Kandrab Basin under the influence of active tectonics.Rank 1 channel anomalies are in addition to the hierarchical anomaly indices and its density in the branching indices.The results of geomorphic indices also indicate uplift of the left bank of the main river due to westward thrust movement of the mainland and this causes drifting of the basin and asymmetry of drainage network in the west coast of the east.Also formed and longitudinal profile and river bed anomalies indicate active tectonics of this basin.The results of geomorphic indices indicate active tectonics of the west of the Kerend basin.The results of morphometric indices, geomorphic indices and evidence of active tectonic geomorphology in the kerend West Basin confirm each other and indicate the active tectonics of the Kerend West Basin.Based on the results of this study, it can be concluded that tectonic activity in the west of the kerend basin is a general uplift of the basin as well as uplift of the left bank of the river due to the kerend active fault movement.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 kerend West basin as well as the entire northwest Zagros range can cause active tectonic hazards such as earthquakes. The anomalies of the drainage network of the Kerend West Basin were evaluated by morphometric indices and their results indicate the existence of hierarchical anomalies in the drainage network of the Kandrab Basin under the influence of active tectonics.Rank 1 channel anomalies are in addition to the hierarchical anomaly indices and its density in the branching indices.The results of geomorphic indices also indicate uplift of the left bank of the main river due to westward thrust movement of the mainland and this causes drifting of the basin and asymmetry of drainage network in the west coast of the east.Also formed and longitudinal profile and river bed anomalies indicate active tectonics of this basin.The results of geomorphic indices indicate active tectonics of the west of the Kerend basin.The results of morphometric indices, geomorphic indices and evidence of active tectonic geomorphology in the kerend West Basin confirm each other and indicate the active tectonics of the Kerend West Basin.Based on the results of this study, it can be concluded that tectonic activity in the west of the kerend basin is a general uplift of the basin as well as uplift of the left bank of the river due to the kerend active fault movement.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 kerend West basin as well as the entire northwest Zagros range can