فهرست مطالب سیده مائده کاوسی داودی

Fault is one of the main processes in tectonics which has relationship with phenomena such as earthquake. Therefore, awareness of the effect of environmental factors on fault occurrence and recognition of high risk areas is very important, that these goals in the present study have been investigated. The research area is Qara-Qum where after determining its faults, altitude, slope, direction, climate, land use, geomorphology, geology, erosion, precipitation, flood zones, pedology, stream power, topographic ruggedness index, distance from road, waterway, anticline and syncline were extracted. Then, data mining algorithms including of decision tree, random forest, cumulative, backing machine, logistic regression and neural network in R software are used to identify the value of variables and bivariate statistical methods including of information value and area density for identification of the values for each variable class fitted in fault occurrence. The accuracy of classification algorithms with ROC curve showed that based on input variables, random forest and support vector machine algorithms with 88% and 86% area under a curve had the best performance in classifying fault occurrence, respectively. Finally, according to the Gini coefficients in random forest algorithm, the zoning maps obtained by combining this algorithm were prepared and validated by bivariate statistical methods. According to this algorithm, the height, pedology and topographic ruggedness index variables, identified as the most important parameters in the fault occurrence respectively. Based on the zoning maps evaluation, information value and area density methods, around 52 and 35 percent of faults placed in very high risk class respectively. Therefore, the information value method was more accurate in identifying fault-sensitive zones. According to the results, data mining methods were introduced as a useful tool in fault risk management. It is also necessary to pay attention to environmental variables, especially topography, during the basin management and land use change stages.

The mass movement of materials on steep slopes under the influence of gravity and motivation factors such as earthquakes, floods and torrential rains called landslide. Landslide similar the other natural phenomena is an important natural disaster that occur every year in the mountainous and highland areas of our country. By risk assessment of landslide occurrence, the sensitive areas with a high potential risk can be identified. Also the effect of different environmental factors on the pattern of high-risk areas can be used in risk management, practically.
One of the basic measures for achieving methods for mass movements control and management is identifying the effective factors in occurrence of this phenomenon. Also, in countries involved in the landslide, there is an increasing tendency for risk and damage assessment of this phenomenon. Therefore, at the present study, using fractal geometry, the effects of land use, geology and geomorphology on the landslide patterns were evaluated in the Tooye-Darvar watershed, Semnan province. Because the fractal theory studies and recent reviews in the earth science indicate that some geological processes such as mineralization, sedimentation, deposition, volcano, morphology and etc have self-similar characteristics. First, using aerial photo interpretation, field surveying and recording the position of landslides using GPS, the landslide distribution map prepared. Then, information layers for each slope, aspect, elevation, geology, geomorphic units, soil erosion class, distance from fault, distance from road, distance from stream and land-use factors prepared.in the ArcGIS software environment using digital elevation model (DEM) of the region with a pixel accuracy of 20 meters. Also the landslides information layer prepared according to the field studies and rasterized. Then, different layers overlapped and table of combined properties for merged layer includes the information of each pixel, extracted and entered into the Excel environment. In Excel, the relative importance (or frequency ratio) calculated for each different class of information layers.
Statistical analysis
After collecting and recording data and creating the database, the SPSS v.23 used for data analysis. In the first stage, the normalization checked using Kolmogorov-Smirnov test at the 5% confidence level. Then, the effect and significance of each measured variable investigated in landslide occurrence.
Calculating the fractal dimension
The landslide areas available in each unit extracted as a polygon and the resulting image transmitted to the Fractalyse software and its fractal dimension calculated using box-counting method. Then, the fractal dimension of landslides placed in work units transferred to the SPSS environment and statistical comparison performed with the aim of investigating the geometric or morphologic differences of sliding zones in different land uses and geologic and geomorphic units. Then to compare the different landslide hazard classes, the density or compression ratio of landslide used in each hazard class. The density ratio calculated by dividing the landslide density in a particular hazard class to the average density of landslides based on the area density or the number of landslides.
landslide susceptibility zonation
In order to zonate the landslide susceptibilityusing bivariate statistical methods, the information value and the area density, each of the factors affecting landslide occurrence include slope and elevation maps, slope aspect, soil erosion class, geomorphic type, geological unit, land use, distance from the stream, distance from the road and distance from fault in GIS environment digitized and classified. Then, based on the two above mentioned methods, the weight of each factor and its related classes determined. The weighted maps of effective factors combined and using natural breaks method, the obtained maps classified in very low, low, moderate, high and very high hazard classes. In order to evaluate the implemented model in the region , 2/3 of landslide points and 2/3 of landslide areas used for modelling and the remaining 1/3 of each one used to evaluate the model.
The results of fractal dimensions study in 146 landslide areas using box counting method showed an average of 1.987. Study of the spatial features in landslide areas include landuse, slope aspect, soil erosion class, geological unit, geomorphic type, height and slope class, distance from road, distance from fault and distance from stream showed that only the effect of geomorphic types on geometric dimension of landslide areas is significant and this significance is caused by high difference (sig=0/000)between mountains and plateaus and upperterraces types. Finally, the density ratio for landslide areas and points in each class of spatial characteristics for landslide occurrence, calculated and the effects of these variables on landslide occurrence severity, presented and analyzed. Also, in the landslide susceptibility zonation about 1/2 of landslides located in the high and very high risk classes that indicates the high potential for landslide in this region.
The results showed that the surface erosion has no significant effect on occurrence of large landslides but it has affected the landslide points. Also, the presence of marl and lime in study area that is a geological unit susceptible to dissolution can be effective in landslide occurrence. Geomorphologically, the mountain and hill types have been effective, which could be due to the high slope of these types. In the case of landslides occurrence in the vicinity of roads, faults and streams, it can be concluded that the small landslides has been affected by road, but it has no significant effect on the occurrence of large landslides. But the existence of fault in the area and proximity to the fault led to the occurrence of extensive landslides. Finally, the presence of stream in the area has also been effective in occurrence of large landslides, but the landslide points, has not been affected by existence of stream in their buffers. Also, high potential for landslide in the study area represents the being endangered for regional installations, agricultural lands, engineering structures and buildings.

The soil erosion affects watershed health and lead to different negative consequences.Marl is an erosion sensitive rock that due to its special physicochemical characteristics,establishment of vegetation on it is difficult,so,it needs to management.One of the soil improvement methods is dynamic compaction,which applies using devices such as rollers.Also,adding pozzolan is another method for soil improvement to modify its physical and mechanical properties.Because the pozzolan in the presence of water,show adhesive properties in a stable and non-solvent form.Therefore,this study tried to evaluate the roles of soil compaction(using rollers having weights of 0,20,25,30and35Kgs)and adding natural pozzolan(in values of 0,50,100,150and200g/m2)in the taftan-pumice type on marl stabilization in Islam-Qaleh region of Razavi-Khorasan.A factorial experimental design done with3replications and totally75field plots with an area equal to30*30centimeters exposed to a rainfall with a10minutes duration and0/8Mm per minute intensity with a slope of15/5°.The results of statistical analysis in the95%confidence level showed that considering runoff,sediment load and sediment concentration variables together,the main effects of soil compaction and pozzolan treatments are significant(sig.=0/000)but their interaction effect isn’t significant(sig.=0/780).Soil compaction treatment has an increasing and significant effect(sig.=0/000)on runoff and sediment production. But the pozzolan treatment showed decreasing and significant effect (sig.=0/000) on sediment and no significant effect (sig.=0/709) on runoff. Also, the interaction effect of 2 treatments on runoff and sediment was not significant. Therefore, the soil compaction due to degradation of surface sealing and marls structure is not suitable, but according to low price and availability of natural pozzolan, for marls stabilization operations, is suggested as an economic and appropriate option.