جستجوی مقالات مرتبط با کلیدواژه « fractal dimension » در نشریات گروه « زمین شناسی »

During the last two decades, the south part of seismotectonic zone of Zagros (Fars) was active. The Zagros seismotectonic belt consists of a series of fault-related folds that within their evolution, seismic areas and hydrocarbon reservoirs formed. Although the characteristics of Zagros are well known, the distribution of active deformations, style of fault-related folds, and its seismotectonic behavior are among the features that require further investigation.    In this study, changes in seismic rate based on changes in seismic parameter (b-value) and fractal dimension of seismicity (D-value) have been investigated using instrumental seismic data in the period of 2000 to 2021. Total amount of b-value and D-value were calculated by the least square’s method and the correlation integral method, respectively. The map of these parameters was plotted by interpolation method.    Frequency-magnitude distribution power law (logN=a–bM) relates the cumulative number of earthquakes (N) to their magnitude (M). This ratio is frequently used in seismic studies. In this relationship, a-value describes the productivity and b-value characterizes relative size distribution of earthquakes. Most b-value studies associate the seismicity parameter with the physical properties of a particular zone.    Since the introduction of fractal in 1976, the fractal concept has covered a wide range of pure mathematics and many experimental aspects of engineering. It has found a comprehensive concept. We analyzed seismicity using the IIEES and IRSC catalog. Decreasing the b-value in the northeastern of study area indicates that stress is increasing, which may signal a future sizable earthquake. The spatial variation of b-value suggests that the SW segment is less stressed compared to the NE segment.Considering that the correlation coefficient is about -0.78, the probability of occurrence of large earthquakes on large area faults increases. The zoning map parameter b-value to D-value ratio found valuable information on the invariance property of the seismic variation scale in the area. These results suggest that this approach can be used as a useful tool to evaluate seismic power distribution on active seismotectonic regions.    According to the zoning maps and the identification of high stress zone in the study area, the north parts of MFF, around Jam and Farashband and in the later stages, Khormuj will be the main candidate areas for future earthquakes. The seismicity pattern analyzed does hold the key to understand the seismotectonics of the region.

The hydrographic network system in a watershed is a function of structural, lithological and topographic factors that are of particular importance in the management of natural resources. The purpose of this study is to compare the performance of two methods without quantification of quantitative parameters in geomorphology including drainage network density and their fractal dimension in the separation of surface geological formations in the northern slopes of Alvand Hamedan. First, by examining the geological map of the region and satellite images of Earth Google and field observations, four geological units including Alvand granite, chlorite hornfels, marl limestone and sterolized schist were selected and in each unit 2 plots of 2 * 2 km were randomly selected. Systematic installation and drainage network and their fractal dimension were calculated using Fractalyse and ArcGIS software and then, QQ diagram, deviation angle and determination coefficient were used for validation. The results show that the validation ratio in both techniques is very good and similar and between 0.97 to 0.99 and indicates the good performance of both techniques to identify and separate geological units. However, considering the QQ diagrams and the proximity of the coefficient determination numbers in the drainage network density technique to 1, plus the low deviation angle and proximity of its computational figures to zero, the results show that the technique without dimensioning the drainage density compared to the fractal dimension technique Drainage network is the best and most appropriate technique for identifying and separating geological units in the study area.

The Bakharden-Quchan Faulted Zone is located in central part of trusted folding belts of Kopeh Dagh in NE-Iran with an array of active right lateral-strike slip faults by trending NW-SE. the most seismic activities have distributed around and along major fault systems of this zone. Because of neotectonic activities and ends bending of these faults in the Bakharden-Quchan Zone and mechanism changing faults to reverse accompanying with trusting vector have increased stress, shortening, seismicity and high density of earthquakes in their ends. This zone has constantly put unter affection neotectonic stresses convergence of Arabia-Eurasia plates since last phase of Alpine orogeny. In this paper by using of Zmap software and Box counting method were used to compute surface fractal dimension of faults distribution that is shown geometric disorder pattern of earthquakes and forming two cells with high fractal dimension along the Bakharden-Quchan Faulted Zone.

Joint roughness coefficient (JRC) is one of the most important properties of discontinuities to determine the amount of shear strength in Barton- Bandis (1982) failure criterion. One of the weaknesses of this parameter is its high dependence on personal judgment in adapting the joint profile to the standard sections of Barton and Choubey (1977). Various methods have been devised to solve this problem, the aim of the paper is a simple formula based on fractal dimension. In this study, two relationships based on fractal dimension by box counting and correlation dimension methods are presented for estimating the joint roughness coefficient. Also, the value of JRC using them is estimated for 192 rock joint profiles and compared with other JRC determination relationships. Accordingly, in these equations, sharing of the asperity amplitude to profile length ratio, in addition to the fractal dimension parameter, increases the accuracy and wider range for calculating the Joint roughness coefficient than single-parameter relations.

The most seismic activities have observed around and along major fault systems of this zone in NE Iran that involving of an array active right lateral-strike slip faults have distributed by trending NW-SE. neotectonic activity and mechanism changing of faults to reverse trusting faults have caused to increase stress, shortening and increasing seismicity with high density of earthquakes in their ends bending. Structural relation faults between this zone and Binaloud through Meshkan thrusting-transfer zone which is major motion engine of Bakharden-Quchan zone to put it constantly under neotectonic stresses convergence of Arabia-Eurasia plates since last phase Alpine orogeny. In this paper Fractal analysis through box counting method has done and D values change between 0-2. If D closes to zero, faults an earthquakes are focusing in a point with high tension and if D closes to 2 is shown low tension, dispersal faults and earthquakes in whole of region. Both surface/volume fractal dimension distribution show higher seismicity activity in Central and Western parts of Kopeh Dagh in NE Iran.

In this paper the fractal dimension of the aftershocks of the 2013 M 7.8 Gosht-Saravan earthquake and their relationship with the seismicity parameters (such as the b-value) and also the released seismic energies of the main shocks and the aftershocks are investigated. The Gosht-Saravan main shock is an intraslab event with normal mechanism. No relationship between the Saravan fault and the main shock is observed. By examining the fractal dimension of the aftershocks and their relationship with the b-value it is confirmed that a linear seismic source (such as a subduction zone) exists. The slip ratio between the primary and secondary faults can be estimated by the fractal dimension. The calculated slip ratio indicates that a low portion of the slips may be related to the near surface fractures which can be verified by the shallow depth aftershocks. The earthquake occurrence in the intermediate depth, releases seismic energy and migrates to the near surface faults and fractures. The occurrence of aftershocks both near the hypocenter and at shallow depths can confirm the activity of these faults. The ratio of the total radiated seimic energy of the aftershocks to the radiated seimic energy of the main shock indicates that a high fraction of the energy related to the main shock and just a small fraction of the energy related to the aftershocks.

The present paper tends to analyze the pore structure of Organic rich carbonaceous rock in 4 samples from Upper Jurassic Sargelu and 5 samples from Lower Cretaceous Garau formation using low pressure nitrogen adsorption. TOC content of Garau samples ranged between 0.64 wt% and 5.21 wt% (mean 3.2 wt%).TOC varied between 0.12 and 10.94 for Sargelu samples. XRD results shows that carbonates are the dominant minerals, followed by quartz and clay minerals. The calculated total pore volume vary between 0.6 cm3/100g to 2.5 cm3/100g with the mean values of 1.4 cm3/100g. A positive linear correlation were found between TOC content of measured samples with pore structure parameters. Due to the larger variation of TOC content this relationship was more obvious for the Sargelu samples. The calculated fractal dimension ranged between 2.45 and 2.81 emphasizing the irregular pore surface of the measured samples. Based on the result of this study organic matter content is recognized as a controlling factor for pore structure and fractal characteristics of the Garau and Sargelu samples.

Fractal analysis of drainages and fractures is a useful tool to determine the maturity structure of a region. With the help of fractal geometry, this study investigates the fractal dimension of drainages and fractures in the southwestern part of Lenjan, and examines the role of geological structures after determining the most active part of region. In order for fractal analysis of fractures and drainages, box-counting method has been used. To achieve this, four parts A, B, C and D of high structural density were first detected in the region, and the fractal dimensions of drainages and fractures were then calculated and compared. Results of fractal analysis of fractures suggest that sector B is the most active part of the region, while fractal analysis of drainages indicates greater tectonic activity in sector A. The larger number of earthquakes and higher density of fractures in sector B, however, could indicate it as the most active part of the study area. Therefore, contradicts in different results obtained from the fractal dimension analysis of fractures and drainages can be explained by the varieties in lithology. The structural studies indicate the existence of a dextral transpression zone in the study area. The dextral transpression zone resulted in uplift of sector B by development of positive flower structures in this part of the region. Therefore, increased tectonic activity in part B is due to formation of positive flower structures and consequent tectonic uplift.

Porous media such as groundwater aquifers, oil and gas reservoirs have a large amount of heterogeneity. Modeling of flow and transport in such environments is based on a survey of the properties of porous media. In this paper, fractal permeability of porous media has been estimated using the Monte Carlo simulation. Using the results of previous studies and measurements on several sandstone samples, such as porosity, fractal dimension, fractal property and intrinsic permeability, using a Monte Carlo probabilistic model and a set of random numbers between 0 and 1 and pore diameter measurement, the sandstone permeability was determined. Finally the simulated and measured values of samples sandstone permeability were compared. Monte Carlo simulation results show that without any need for empirical coefficients, domain discretization with only a few laboratories measured parameters one can reasonably determine the fractal permeability of porous media. Measured and calculated permeability correlations are matched 83 percent.

In this study active faults in the region of Shahid Rajai dam of sari with 100 km radius was categorized on based fractal dimension of faulting and Earthquake and also evaluating of slip rate and investigate those activity rate. Using the fractal dimension of faulting and earthquake with squares method (Box-counting) and finally by classification this fractals dimension، the faults of North Alborz، Damghan and Garmsar more activity faults in the region of study area during 100 years late which based on activity degree of faulting and Earthquake with method of fractal analysis which based on assessment of activity degree of faulting and earthquake with method of fractal analysis also set in BD grade and this activity was confirmation. For assessment of slip rate beginning the seismicity parameters (a&b) of study area was determination، then these parameters were normalized for each fault. Based on existing relationships and having a&b for each fault، the seismic moment those fault was calculated. According to The relationships for calculating the rate of seismic moment، slip rate of each fault has been estimate and based on faults in study area was classification. The Faults with very low slip rate and high return period of earthquake could cause occurrence large earhquakes which earthquake of 856 A. D Qumes and causing smith therefore Damghan Fault could this fault know. Thereupon Therefore expectance larger slip in the future on faults such as Astaneh، Rameh، Cheshme-Ali and etc Will have. High slip rate along the New faults introduced (Khorram-Abad، Majid، etc.) in this area is noteworthy that according to occurrence the earthquakes in the privacy of their fault، the high slip rate is reasonable.

In this research, to investigate seismic pattern and precursory properties of fractal dimensions, spatial distribution and temporal variations of correlation dimensions of epicentral, De, and temporal distribution of earthquakes, Dt, before the Baladeh-Kojour earthquake have been studied. The May 28th, 2004, Baladeh-Kojour earthquake with Mb= 6.2 (ISC), which is one of the largest earthquake in the vicinity of Tehran, was occurred in the northern part of the Alborz mountain ranges. The spatial distribution maps show decreasing in De and Dt in the eastern part of the epicenter, which is observed at 2002 in the temporal variation plots. With respect to space-time plot, it seems that this decreasing caused by the earthquake clusters that were occurred between 2002 -2003. Investigation of seismic pattern based on spatial and temporal variations of fractal dimensions and space-time plot of earthquakes demonstrate doughnut pattern (some earthquake clusters and a lot of small events) and seismic quiescence before the main shock. The results indicate that fractal dimensions are sensitive to clustering in space and time. So, the spatial and temporal variations of these parameters can be used as a precursory phenomenon, which is caused by seismic activation and quiescence.

In exploratory geophysics, main and primary purposes are determination of researching targets densities, which have a particular density difference with that of the host rock. In this study, hence, we introduce new method for density determination, called "variogram method”, which is based on the fractal geometry. It is based on minimizing the Bouguer anomaly surface roughness in which fractal dimension of the surface is used as Bouguer anomaly surface roughness criterion. Through this method, we can determine the optimum density of charak in the South Hormozgan, which is utilized in order to accomplish some corrections and review their results about isostatic circumstances of those regions. There are various methods to illustrate the bedrock topography and we will explain one of these methods at the present paper. The calculation is dome in the Fournier domain. The method mentioned above was implemented to detect the bedrock topography and the results were compatible to the region geology.