ارزیابی وضعیت تکتونیک فعال با استفاده از تحلیل پارامترهای ژئومورفیک و مورفومتریک (مطالعه ی موردی: حوضه های غرب استان کرمانشاه) (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
از دیدگاه زمین ساختی، زون زمین شناسی زاگرس یک منطقه ی فعال تکتونیکی بوده و شواهد ژئومورفیک حرکات نو زمین ساختی در این منطقه قابل شناسایی و ردیابی است. حوضه های غرب استان کرمانشاه در زون زاگرس واقع شده و به نظر می رسد به علت قرارگیری گسل زاگرس مرتفع، گسل ذهاب-کرند و گسل قصر شیرین-گیلانغرب در این محدوده ، این حوضه ها از نظر تکتونیکی فعال باشند؛ بنابراین مطالعه ی تکتونیک فعال این محدوده با استفاده از پارامترهای ژئومورفیک و مورفومتریک می تواند منجر به شناخت جامع از وضعیت تکتونیک فعال این حوضه ها گردد؛ بنابراین هدف این پژوهش، ارزیابی وضعیت تکتونیک فعال حوضه های غرب استان کرمانشاه است. بر این اساس ابتدا محدوده ی حوضه های موردمطالعه، شبکه ی زهکشی آن ها و ویژگی های مورفومتری و توپوگرافی بر اساس DEM سی متر منطقه، استخراج گردید. در ادامه بر اساس شاخص های ژئومورفیک (AF، Hi،SL، BS) و شاخص های مورفومتری (Dd،R، Rr، Hd) وضعیت فعالیت تکتونیکی حوضه های موردمطالعه ارزیابی شده و نتایج حاصل از آن ها بر اساس ویژگی های لیتولوژیکی و ساختاری حوضه ها مورد ارزیابی قرار گرفت. نتایج نشان داد که محدوده ی غرب استان کرمانشاه بر اساس نتایج پارامترهای مورفومتریک و ژئومورفیک از نظر تکتونیکی فعال بوده، اما میزان این فعالیت با توجه به شرایط لیتولوژیکی و ساختاری حوضه ها از شدت و ضعف برخوردار است. در این میان، پارامترهای مورفومتریک به علت استانداردسازی قادر به بازتاب شرایط لیتولوژیکی و ساختاری حوضه ها در طبقه بندی نهایی فعالیت تکتونیکی بوده و به نظر می رسد پارامترهای مورفومتریک در حوضه های با تنوع لیتولوژیکی بالا، کارایی بهتری برای ارزیابی وضعیت تکتونیک فعال دارند.Assessment of Active Tectonic Status Using Analysis of Geomorphic and Morphometric Parameters (Case Study: West Basins of Kermanshah Province)
introduction
Active tectonic studies are one of the most important topics in earth science and their results are widely used for assessing natural hazards and land use development and management plans in populated areas (Pedra et al., 2009, 220).Among these, geomorphic indices have been effective in assessing active teconic in large areas due to their high speed and accuracy (Clare & Pinter, 2002, 154).And are used to understand geomorphic processes, basin uplift velocity, and landform classification (Widget et al., 2017, 42).In tectonic active zones, the drainage network has shown the relationship between surface processes and structural changes (Delkailaw et al. 2006,244).Morphometric parameters are therefore highly efficient in identifying tectonic active zones (Chen et al., 2003, 115).
Iran is tectonically active due to its continental convergence belt and 50% of recorded earthquakes occur in the Zagros Zone (Mirzai 1997; 40). The studied basins are located west of Kermanshah province in the Zagros Zone and the Zagros Fault, Zahab - Kandand Fault and Ghasr Shirin - Gilan Gharb Fault are in the range of these basins. These faults are mainly seismic.7.3 Richter Earthquake and Decades An earthquake measuring more than 5 Richter occurred in this area, due to the cities of Gilan West, Cradle, Karrand West, Ghasr Shirin, Sarpolzahab, Azg, Akhaliabad and Javanrood and many more. In the basins of these basins, the assessment of their active tectonic status seems necessary. Therefore, the purpose of this study is to evaluate the active tectonics and its classification in the studied basins.
materials and methods
The present research is based on descriptive-analytical, library methods and calculation of geomorphic and morphometric parameters.The research data include DEM SRTM symmetry, 1: 250000 geological map and 1: 50000 topographic maps.In this study, first using the DEM 30 m area of the catchment area and drainage network of the studied basins were extracted and then the topographic and morphometric characteristics of the basins were calculated.Then the geomorphic parameters of SL, Af, Bs and Hi were calculated (Table 1) and classified according to the classification of Qing et al. (2016) (Table 2).Then, the Active Tectonic Ratio Index (IRAT) was calculated based on (1).The morphometric parameters used in this study include Dd, R, Rh and Hd (Table 3).The degree of tectonic activity was calculated based on Morphometric Parameters (2) presented by Davies (1975) and based on the results, the tectonic activities of the region were divided into five zones with very low to very high activity. Finally, based on the findings of the study and considering the geological conditions of the studied basins, the active tectonic status is determined.
Findings
The AF parameter in the studied basins ranged from 23% to 63% (Table 2) and showed low tectonic activity in Gilan West, Zemkan, Flock and Zahab basins, Kafravar and Karrand basins with moderate tectonic activity and Sarpole and Qasr Shirin basins have high tectonic activity.
Hypsometric integral parameter values in the studied basins ranged from 0.19 to 0.48, with moderate tectonic activity, low-tectonic activity, Gilan-west, Karand-west and Sar-e Pol basins with low tectonic activity and flock-catchment. And the palaces have very low tectonic activity.
The values of SL index in the studied basins varied from 122 to 1569. Accordingly, the Kandar West Basin has moderate tectonic activity, Gilan West and Ghasr Shirin basins have high tectonic activity and Zakkan, Sarpol, Azaleh and Zabab basins have high tectonic activity. . The Bs index values in the studied basins varied from 0.83 to 4.70. According to this index, Qasr Shirin basin has high tectonic activity and other basins have high tectonic activity. IRAT index values in the western basins of Kermanshah province are between 3.25 to 4 and indicate high and very high tectonic activity in the studied basins. The drainage density parameter values of the studied basins are between 2.32 to 4.21 and these values indicate moderate to high tectonic activity. Roughness parameter values of the studied basins vary between 915 and 2169 m.Basins of Qasr Shirin and Karand West based on roughness values have low and moderate tectonic activity respectively and other basins have high tectonic activity.Parameter values of roughness ratio in the studied basins are between 0.016 to 0.059 and accordingly, Zahab basin has moderate tectonic activity and other basins have low tectonic activity.Roughness index in the studied bins show values between 2.73 to 9.02. Based on the values of this parameter, west west basin has moderate tectonic activity and other basins have high tectonic activity.
Conclusion
The results showed that the different lithological and structural features of the basins did not have significant effect on the final result of geomorphic and IRAT indexes and all basins had high to very high tectonic activity conditions.Results of morphometric indices and DAT index reflected the effects of basin lithological diversity on the final result.Also, contrary to the results of geomorphic indices, all basins are classified into two classes of tectonic activity based on morphometric indices of the studied basins are classified into three classes of moderate, high and very high tectonic activity. Finally, it can be stated that the studied basins in west of Kermanshah province are tectonically active based on the results of morphometric and geomorphic parameters. However, the tectonic activity of the basins due to the geological conditions has intensity and weakness and morphometric parameters are able to reflect lithological and structural conditions due to standardization.Therefore, it seems that morphometric parameters in watersheds with high lithological diversity are better able to evaluate active tectonic status.
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