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Volume 18, Issue 3 (Fall 2014)
Abstract
Mass movement occurrence in its various forms in mountainous areas causes a lot of human and financial losses yearly. Thus, it is necessary to identify and prioritize vulnerable places and prepare a specific regional plan to decrease occurrence and losses due to landslide in prone areas. Syahkooh anticline is one of the region which, signs of numerous landslide can be seen through all it. In this research, after identification of effective factors using Entropy model, these factors were investigated, an Entropy matrix produced and zoning map of landslide prepared and finally to reduce its damages some solutions have been suggested. The results show that distance of fault 46.06%, elevation 28.26%, slope 17.54%, lithology 7.14% and aspect 1% had been affected. Zoning map shows low risk areas only include 21.76% of the region and 78.23% of the region lied on the side of high and moderate risk zones, which states the high potential area of landslide occurrence in the area. The proposed solutions are construction away from faults and steep Asmari formation, increase in the level of protection of roads, control of Drilling and excavation in Asmari formation. These are the most important measures to reduce losses mass movement in the Syahkooh anticline.
Volume 24, Issue 4 (Winter 2020)
Abstract
Introduction
In order to tectonic analysis northwestern Zagros, we have used fractal geometry against classic geometry and fuzzy logic instead of Aristotelian classic logic to evaluate natural landscapes with non-integer dimension and the complex nature of tectonic processes. The fractal dimension (FD) has been applied to determine anomaly or normality of surface rupture (faults) pattern in association with drainage network that can show the maturity of structures. In other hand, uncertainty of fuzzy logic has been applied to specify the potential of tectonic activity by using morphotectonic factors. At the end, we have compared results of these two methods with surface epicenters of earthquakes.
Methodology
To calculate the FD of faults and drainage network using box-counting, the area was divided to 6 boxes that contain main fault trends horizontally and vertically. In fractal method each box is covered by several network (grid) that their side length (quantity of Size) is decreased at every grid level. Then the relation between reciprocal of side length and boxes containing linear feature (quantity of Number) was drawn Logarithmically as a linear regression that shows FD. In fuzzy model, six main effective factors were determined and 12 layers were produced base on their importance in tectonic analysis. The membership degree of these layers’ effective parts by fuzzy functions were determined and then they were overlaid by fuzzy operators like gamma with different powers.
Results and Discussion
Calculating number-size quantity using box-counting method for faults and drainage network shows both partial and overall FD changes. As partial changes are close, yjey indicate the existence of the self-similarity components. Based on partial FD, there are three communities: back ground with FD larger than slope of linear regression, threshold community with repeating component, and anomaly community with FD value more than three. Based on overall FD, development of faults and drainage network have not entered to chaos phase. The comparison of mean value of fuzzy zoning with different gamma powers for each box indicates that 0.7 power of gamma has the most correlation with overall FD of boxes.
Conclusion
Areas of high value of FD for faults and low value for drainage network are more tectonically active. Here the box labeled A which represent western parts of Kermanshah in folded Zagros, has the highest FD value of faults (1.32) and lower FD value of drainage network (1.432). Epicenter evidences of earthquakes for example 7.3 magnitude earthquake of Ezgeleh, confirm the FD results; whereas, the box labeled E near Dezful Embayment shows the lowest FD value of faults (1.07) and highest FD value of drainage network (1/470). Overlaying fractal boxes (A to F) with fuzzy exports (gamma 0.7) are in line with these results and represent more potential of tectonic activity for northwestern parts of area (box A).
Keywords: Tectonic, Northwestern Zagros, Fractal, Fuzzy.Introduction
In order to tectonic analysis northwestern Zagros, we have used fractal geometry against classic geometry and fuzzy logic instead of Aristotelian classic logic to evaluate natural landscapes with non-integer dimension and the complex nature of tectonic processes. The fractal dimension (FD) has been applied to determine anomaly or normality of surface rupture (faults) pattern in association with drainage network that can show the maturity of structures. In other hand, uncertainty of fuzzy logic has been applied to specify the potential of tectonic activity by using morphotectonic factors. At the end, we have compared results of these two methods with surface epicenters of earthquakes.
Methodology
To calculate the FD of faults and drainage network using box-counting, the area was divided to 6 boxes that contain main fault trends horizontally and vertically. In fractal method each box is covered by several network (grid) that their side length (quantity of Size) is decreased at every grid level. Then the relation between reciprocal of side length and boxes containing linear feature (quantity of Number) was drawn Logarithmically as a linear regression that shows FD. In fuzzy model, six main effective factors were determined and 12 layers were produced base on their importance in tectonic analysis. The membership degree of these layers’ effective parts by fuzzy functions were determined and then they were overlaid by fuzzy operators like gamma with different powers.
Results and Discussion
Calculating number-size quantity using box-counting method for faults and drainage network shows both partial and overall FD changes. As partial changes are close, yjey indicate the existence of the self-similarity components. Based on partial FD, there are three communities: back ground with FD larger than slope of linear regression, threshold community with repeating component, and anomaly community with FD value more than three. Based on overall FD, development of faults and drainage network have not entered to chaos phase. The comparison of mean value of fuzzy zoning with different gamma powers for each box indicates that 0.7 power of gamma has the most correlation with overall FD of boxes.
Conclusion
Areas of high value of FD for faults and low value for drainage network are more tectonically active. Here the box labeled A which represent western parts of Kermanshah in folded Zagros, has the highest FD value of faults (1.32) and lower FD value of drainage network (1.432). Epicenter evidences of earthquakes for example 7.3 magnitude earthquake of Ezgeleh, confirm the FD results; whereas, the box labeled E near Dezful Embayment shows the lowest FD value of faults (1.07) and highest FD value of drainage network (1/470). Overlaying fractal boxes (A to F) with fuzzy exports (gamma 0.7) are in line with these results and represent more potential of tectonic activity for northwestern parts of area (box A).
Keywords: Tectonic, Northwestern Zagros, Fractal, Fuzzy.
Volume 25, Issue 2 (Summer 2021)
Abstract
Nowadays, given the rapid growth of population, development of infrastructure is inevitable and the pressure of human needs on the soil and exploitation of areas around cities in rural areas are increasing. Access to surface water, fertile soil, groundwater, access to transit roads, etc. have made establishing of new cities compulsory despite the environmental hazards in those areas.
Land deformation as an environmental hazard may be related to tectonic activities such as earthquakes, faults, volcanoes, landslides and anthropogenic processes such as groundwater exploitation, which threaten urban areas. Land surface subsidence is recognized as a potential problem in many areas. This phenomenon is most often caused by human activities, mainly from the removal of subsurface water. Also, Iran with rough and mostly mountainous topography, have a high potential for landslides and instability of slopes.
Pardis new city in the east part of Tehran is one of the areas most prone to Domain Instabilities. The location of the city and its expansion toward the steep slopes have made it susceptible to all kinds of natural hazards, so the main purpose of the study is investigate the potential of landslide and subsidence in Pardis.
Material and Methods
This research consists of two stages: first, ground surface deformation was estimated using radar interferometry technique. Then, landslide susceptible zoning was carried out using Fuzzy and AHP methods.
We applied SBAS algorithm to the 27 SAR images of the Sentinel-1 satellite, in ascending orbit for the time period of 2016.01.06.-2018.12.21. The first step of the SBAS procedure involves the selection of the SAR data pairs to generate the interferograms; the selected images are characterized by a small temporal and spatial separation (baseline) between the orbits in order to limit the noise effect usually referred to as decorrelation phenomena. The second step of the procedure involves the retrieval of the original (unwrapped) phase signals from the modulo-2 π restricted (wrapped) phases directly computed from the interferograms.
In the next stage, landslide susceptibility zones have been evaluated using both fuzzy logic and analytical hierarchy process (AHP) models, as a weighting technique to explore landslide susceptibility mapping. In the modelling process, eight causative variables including aspect, slope degree, altitude, distance from the road, distance from the fault, distance from the river, lithology and land use were identified for landslide susceptibility mapping.
In fuzzy logic the degree of membership of variables may be any real number from 0 (non-membership) to 1 (full membership) which reflects a degree of membership (Zadeh, 1965). By contrast, in Boolean logic, the truth values of variables may only be the integer values 0 or 1. After Fuzzification of all layers, since the causative factors are not the same value, the AHP method to determine the weights was performed. The AHP methodology consists of pairwise comparison of all possible pairs of factors. The relative rating for the dominance between each pair of factors was guided by expert knowledge. After obtaining weight of each factors, these weights are multiplied in the map calculated by fuzzy membership.
Results and Discussion
We used 27 c-band sentinel-1 images for the 2016-2018 period and the Small BAseline Subset (SBAS) approach to investigate land deformation in Pardis. Result of the deformation map of Pardis show that the northern part is uplifted with an annual rate of 25 mm/yr. The uplift of the northern part can be attributed to tectonic factors and the southern part of the basin subsided with an annual rate of -35 mm/yr. Thereafter landslide susceptibility areas have been evaluated. Geomorphological variables (slope, aspect, elevation, river), geology variables (lithology, fault) and anthropogenic variables (land use, roads) have been used for generation of the landslide susceptible map. The results of the landslide susceptible map indicate that the northern part of the Pardis basin have a high potential for landslides. Landslide susceptible map is classified into five classes: very high, high, medium, low and very low.
Medium to very high susceptible class covered 40% of the study area which overlay on uplifting areas resulting from radar technique.
Conclusion
SBAS time series method has been used to detect ground surface deformation and vertical movements. This method is based on an appropriate combination of multi look DInSAR Interferograms. Deformation map indicate that northern part of the basin, uplifted and southern part subsided. The cities of Pardis, Roodehen and Boomehen in the southern part, subsided a mean rate of respectively -35, -31 and -29 mm/year. The northern part uplifted with a mean rate of 25 mm/year which can be attributed to tectonic activity. Then, the landslide susceptibility map was created using both Fuzzy and AHP methods. The result show that more than 40% of the basin is exposed to landslides. The results of both methods SBAS time series analysis, landslide susceptibility mapping, demonstrated domain instabilities in northern part of the basin. As a result, identifying instable areas seems necessary for the urban development of the Pardis.
Key words: Pardis city, SBAS time series analysis, landslide, subsidence
Land deformation as an environmental hazard may be related to tectonic activities such as earthquakes, faults, volcanoes, landslides and anthropogenic processes such as groundwater exploitation, which threaten urban areas. Land surface subsidence is recognized as a potential problem in many areas. This phenomenon is most often caused by human activities, mainly from the removal of subsurface water. Also, Iran with rough and mostly mountainous topography, have a high potential for landslides and instability of slopes.
Pardis new city in the east part of Tehran is one of the areas most prone to Domain Instabilities. The location of the city and its expansion toward the steep slopes have made it susceptible to all kinds of natural hazards, so the main purpose of the study is investigate the potential of landslide and subsidence in Pardis.
Material and Methods
This research consists of two stages: first, ground surface deformation was estimated using radar interferometry technique. Then, landslide susceptible zoning was carried out using Fuzzy and AHP methods.
We applied SBAS algorithm to the 27 SAR images of the Sentinel-1 satellite, in ascending orbit for the time period of 2016.01.06.-2018.12.21. The first step of the SBAS procedure involves the selection of the SAR data pairs to generate the interferograms; the selected images are characterized by a small temporal and spatial separation (baseline) between the orbits in order to limit the noise effect usually referred to as decorrelation phenomena. The second step of the procedure involves the retrieval of the original (unwrapped) phase signals from the modulo-2 π restricted (wrapped) phases directly computed from the interferograms.
In the next stage, landslide susceptibility zones have been evaluated using both fuzzy logic and analytical hierarchy process (AHP) models, as a weighting technique to explore landslide susceptibility mapping. In the modelling process, eight causative variables including aspect, slope degree, altitude, distance from the road, distance from the fault, distance from the river, lithology and land use were identified for landslide susceptibility mapping.
In fuzzy logic the degree of membership of variables may be any real number from 0 (non-membership) to 1 (full membership) which reflects a degree of membership (Zadeh, 1965). By contrast, in Boolean logic, the truth values of variables may only be the integer values 0 or 1. After Fuzzification of all layers, since the causative factors are not the same value, the AHP method to determine the weights was performed. The AHP methodology consists of pairwise comparison of all possible pairs of factors. The relative rating for the dominance between each pair of factors was guided by expert knowledge. After obtaining weight of each factors, these weights are multiplied in the map calculated by fuzzy membership.
Results and Discussion
We used 27 c-band sentinel-1 images for the 2016-2018 period and the Small BAseline Subset (SBAS) approach to investigate land deformation in Pardis. Result of the deformation map of Pardis show that the northern part is uplifted with an annual rate of 25 mm/yr. The uplift of the northern part can be attributed to tectonic factors and the southern part of the basin subsided with an annual rate of -35 mm/yr. Thereafter landslide susceptibility areas have been evaluated. Geomorphological variables (slope, aspect, elevation, river), geology variables (lithology, fault) and anthropogenic variables (land use, roads) have been used for generation of the landslide susceptible map. The results of the landslide susceptible map indicate that the northern part of the Pardis basin have a high potential for landslides. Landslide susceptible map is classified into five classes: very high, high, medium, low and very low.
Medium to very high susceptible class covered 40% of the study area which overlay on uplifting areas resulting from radar technique.
Conclusion
SBAS time series method has been used to detect ground surface deformation and vertical movements. This method is based on an appropriate combination of multi look DInSAR Interferograms. Deformation map indicate that northern part of the basin, uplifted and southern part subsided. The cities of Pardis, Roodehen and Boomehen in the southern part, subsided a mean rate of respectively -35, -31 and -29 mm/year. The northern part uplifted with a mean rate of 25 mm/year which can be attributed to tectonic activity. Then, the landslide susceptibility map was created using both Fuzzy and AHP methods. The result show that more than 40% of the basin is exposed to landslides. The results of both methods SBAS time series analysis, landslide susceptibility mapping, demonstrated domain instabilities in northern part of the basin. As a result, identifying instable areas seems necessary for the urban development of the Pardis.
Key words: Pardis city, SBAS time series analysis, landslide, subsidence
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