تفکیک حساسیت سازندهای زمین شناسی دامنه های شمالی الوند همدان با استفاده از رابطه بعد فراکتال شبکه زهکشی

ابعاد فراکتالی شبکه زهکشی‌، معرف میزان تشابه ژئومورفولوژیکی در بین آن‌ها و تابعی از عوامل ساختمانی‌، لیتولوژی و توپوگرافی میباشد. لذا هدف از این پژوهش تعیین بعدفراکتال شبکه زهکشی و بررسی ارتباط آن با میزان حساسیت سازندهای زمین‌شناسی به فرسایش در دامنه‌های شمالی الوند همدان است‌. ابتدا چهار سازند شامل‌، گرانیت‌، هورنفلس کلریت‌دار، سنگ آهک مارنی و شیست، ‌ از طریق تصاویر گوگل ارث و نقشه زمین‌شناسی منطقه ا‌نتخاب شد‌. سپس در هر واحد زمین‌شناسی تعداد 2 پلات 22 کیلومتر تعیین و با استفاده ازنرم‌افزار fractalyse ابعاد فراکتال آنها محاسبه شد نتایج نشان داد که بشترین مقدار بعد فراکتال‌ به ترتیب مربوط به سازند هورنفلس کلریت‌دار با مقدار ‌ 1.33، سنگ آهک مارنی 1.31، شیست استرولیت‌دار 1.27 و گرانیت الوند 1.22 است نتایج تحلیل آماری مقادیر rmse و r2 نشان می‌دهد که در پلات‌های 1 و 3 با کمترین خطا و در پلات‌های 4 و 6 و 7 دارای تطابق نسبتاً خوب و در پلات‌های 2 و 5 و 8 با بیشترین خطا کمترین تطابق وجود دارد. بنتایج بررسی‌ آزمون پیرسون ‌و مقدار همبستگی نشان می‌دهد که بین مقاومت سازند‌ها و بعد فراکتال آن‌ها ارتباط معنی‌دار و معکوس وجود دارد و با افزایش مقاومت سازندها به فرسایش بعد فراکتال آن‌ها کاهش می‌یابد و تراکم زهکشی هم پایین است‌. با توجه به نتایج‌ حاصله و قابل قبول‌ می‌توان‌ با استفاده از تکنیک بعد فراکتال شبکه زهکشی‌، نوع سازندها و حساسیت آن‌ها به فرسایش را با ‌صرف هزینه کم و سریع‌تر تفکیک و بررسی نمود‌.

sensitivity separation of geological formations of northern slopes of alvand hamedan using fractal dimension of drainage network

extended abstractintroductionin the last decade, the use of fractal analysis to quantitatively describe the geomorphological and hydrological watersheds has increased and the main purpose of most of these studies is to find a mathematical relationship between the geomorphological characteristics of the basin and issues such as erodibility of formations and segregation of geological units. alimoradi et al. (2015), in calculating the fractal dimension of geological formations and examining its relationship with the sensitivity of formations, showed that there is a significant relationship between fractal number and the sensitivity of basin formations to erosion. barzegari dehj et al. (2019) in comparing the dimensionless index of drainage network density and fractal dimension of drainage network in the separation of lithological units of taft watershed, yazd, concluded that the drainage network density technique compared to the fractal dimension of drainage network technique in identifying and separation of geological units of the region has provided excellent results. donadio et al. (2014) compared three rivers from a fractal point of view of the hydrographic model and concluded that the relationship between tectonics and erosion is very high with the fractal dimension number. hui et al. (2017) in examining the relationship between fractal dimension of drainage network and evolutionary stages of erosion of china yellow basin showed that fractal values of drainage network have a positive and linear relationship with sediment delivery and runoff values of the basin.methodologyalvand mountain massif of hamedan is located in the division of tectonic units of iran in the structural zone of sanandaj-sirjan, which extends parallel to the zagros rotation. the purpose of this study is to determine the fractal dimension of the drainage network and to investigate its relationship with geomorphological patterns and the sensitivity of geological landslides to erosion in the northern slopes of alvand hamedan. in this study, four geological units including granite, chlorite hornfels, marl limestone and sterolized schist were first selected using google earth software, geological map of the area and satellite images and field visits. then, in each geological unit, 2 plots of 2*2 km were determined and their fractal dimensions were calculated using fractalyse software. after calculating the fractal dimension and determining the sensitivity of each formation, the relationship between the fractal dimension and the formations was investigated by pearson test and the correlation value.results and discussion the results showed that the highest amount of fractal dimension is related to chlorinated hornfels formation with 1.33, marl limestone 1.31, sterolized schist 1.27 and alvand granite 1.22, respectively. examination of the coefficient and deviation angle data in each of the geological units shows that these values are somewhat high in the fractal dimension technique of the drainage network. so that the deflection angle is 1.909 in sterolized schist, 1.555 in granite, 1.528 in hornfels and 1.171 in marl limestone. studies show that the computational values of the fractal dimension of the drainage network are very good and in the amount of 0.99 and indicate the good performance of the fractal dimension technique for identifying and separating the geological units of the region. due to the proximity of the coefficient of determination in the fractal dimension technique of drainage network density to 1, low deflection angle and proximity of its computational figures to zero, the fractal dimension technique of drainage network is the best and most appropriate technique for separating geological units in the study area. studies show that in formations with more sensitivity than resistant formations, more changes occur in drainage density and their fractal dimension is more.