@article { author = {Nikfal, Amirhossein and Ranjbar SaadatAbadi, Abbas and Rahnama, Mehdi and tajbakhsh, sahar and Moradi, Mohamad}, title = {Evaluation of the WRF/Chem aerosol models - a dust episode case study}, journal = {Iranian Journal of Geophysics}, volume = {14}, number = {4}, pages = {1-18}, year = {2020}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {10.30499/ijg.2020.104569}, abstract = {Presented herein is an analysis of an intensive dust intrusion of 8-11 February, 2015. The intrusion has been associated with the development of an intense front over the Middle East. During the episode, dust concentrations in Ahvaz air quality monitoring station in south-western Iran (Khuzestan region) reached over 10000 μg/m3, which was beyond the capacity of air quality sensors to be recorded. In this paper, the performance of WRF/Chem modelling system was evaluated for the west and southwestern Iran as well as the whole model domain. MADE and GOCART models as the main aerosol models implemented in WRF/Chem V3.6 were verified by ground observation data for the specific points. We have taken into account the advantages and disadvantages of MADE and GOCART aerosol models over the study period, by comparing the simulations' results for the specific points with the available dust concentration data. The time series of the area-average of modeled dust column mass density over the test area determined a coherent temporal variation with that of MERRA-2 model which shows the sensitivity of WRF/Chem modeling system for this area with most frequent dust storm events in the Middle East. The validation of WRF/Chem V3.6 modeling system results for the overall model domain is implemented using Hovmoller diagrams. The modeled latitude-average of dust column mass density for the whole model domain showed some discrepancies of dust transport pattern with the results of MERRA-2 model. Although there is a considerable difference between the modelled dust concentrations and the observations especially on the peak values, the temporal variations of the modelled dust concentration with MADE aerosol model is quite consistent with the observations. The results of MADE aerosol model for the dust concentration were more close to the observations of the points inside Khuzestan and surrounding low level plains with aeolian soils. The GOCART aerosol model had more reasonable simulation results for the points through the mountainous terrains of western Iran. It can be concluded that the structure of MADE and GOCART aerosol models can be revised with regard to their relative advantages in specific regions to minimize the error in modeling dust behavior. Scince this study has been employed on a dust episode, and considering that the gaseous air pollutants require the emissions data, the simulations of the gaseous aerosols has not been considered in this study. However, the results of the WRF/Chem model for the dust aerosols could be extended to the other aerosols, especially PM10 and PM2.5 particles.  }, keywords = {WRF/Chem,Dust,Aerosol models,Middle East}, title_fa = {Evaluation of the WRF/Chem aerosol models - a dust episode case study}, abstract_fa = {Presented herein is an analysis of an intensive dust intrusion of 8-11 February, 2015. The intrusion has been associated with the development of an intense front over the Middle East. During the episode, dust concentrations in Ahvaz air quality monitoring station in south-western Iran (Khuzestan region) reached over 10000 μg/m3, which was beyond the capacity of air quality sensors to be recorded. In this paper, the performance of WRF/Chem modelling system was evaluated for the west and southwestern Iran as well as the whole model domain. MADE and GOCART models as the main aerosol models implemented in WRF/Chem V3.6 were verified by ground observation data for the specific points. We have taken into account the advantages and disadvantages of MADE and GOCART aerosol models over the study period, by comparing the simulations' results for the specific points with the available dust concentration data. The time series of the area-average of modeled dust column mass density over the test area determined a coherent temporal variation with that of MERRA-2 model which shows the sensitivity of WRF/Chem modeling system for this area with most frequent dust storm events in the Middle East. The validation of WRF/Chem V3.6 modeling system results for the overall model domain is implemented using Hovmoller diagrams. The modeled latitude-average of dust column mass density for the whole model domain showed some discrepancies of dust transport pattern with the results of MERRA-2 model. Although there is a considerable difference between the modelled dust concentrations and the observations especially on the peak values, the temporal variations of the modelled dust concentration with MADE aerosol model is quite consistent with the observations. The results of MADE aerosol model for the dust concentration were more close to the observations of the points inside Khuzestan and surrounding low level plains with aeolian soils. The GOCART aerosol model had more reasonable simulation results for the points through the mountainous terrains of western Iran. It can be concluded that the structure of MADE and GOCART aerosol models can be revised with regard to their relative advantages in specific regions to minimize the error in modeling dust behavior. Scince this study has been employed on a dust episode, and considering that the gaseous air pollutants require the emissions data, the simulations of the gaseous aerosols has not been considered in this study. However, the results of the WRF/Chem model for the dust aerosols could be extended to the other aerosols, especially PM10 and PM2.5 particles.  }, keywords_fa = {WRF/Chem,Dust,Aerosol models,Middle East}, url = {https://www.ijgeophysics.ir/article_104569.html}, eprint = {https://www.ijgeophysics.ir/article_104569_c2a6d3c4fbd01cbc8e610b3eb8d1ec48.pdf} } @article { author = {taghizadeh Farahmand, Fataneh and Eslami, Malikeh}, title = {Evaluation of the Deterministic Seismic Hazard by using Fuzzy Inference System, Case Study: Tabriz city, Iran}, journal = {Iranian Journal of Geophysics}, volume = {14}, number = {4}, pages = {19-28}, year = {2020}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {10.30499/ijg.2020.107051}, abstract = {The Iranian plateau is located in the high seismicity belt. Earthquake can inflict severe loss of life and property, especially when they occur in densely populated areas. Therefore, seismic hazard evaluation is very essential to prevent the harmful effects. The region of the study is located in the northwest of Iran, between 43°-50° E longitude and 35.5°-40.5° N latitude. This city which is located in the center of East Azerbaijan province, has been ruined by terrible earthquakes, which is due to the presence of active faults in the region. Seismic hazard assessment similar to other seismology researches is very complicated due to the effect of different parameters in an earthquake occurring with uncertainty. The amount of uncertainty should be considered in a rational way. The fuzzy method is a suitable method that is used as a decision-making method for solving problems and modeling uncertainties and ambiguities. We used a fuzzy inference system, as the practice is based on uncertainty estimation of seismic hazard for Tabriz region. Peak ground Acceleration value is estimated for fuzzy Logic System in deterministic method 0.55g which is obtained from a seismic source with a Mmax=8.0 at a distance of  36.98 km of Tabriz city.The contour map of the peak ground acceleration throughout Tabriz city can help in urban planning.  }, keywords = {Fuzzy inference system,Seismic hazard,Deterministic Approach,Peak Ground Acceleration,Tabriz,Iran}, title_fa = {Evaluation of the Deterministic Seismic Hazard by using Fuzzy Inference System, Case Study: Tabriz city, Iran}, abstract_fa = {The Iranian plateau is located in the high seismicity belt. Earthquake can inflict severe loss of life and property, especially when they occur in densely populated areas. Therefore, seismic hazard evaluation is very essential to prevent the harmful effects. The region of the study is located in the northwest of Iran, between 43°-50° E longitude and 35.5°-40.5° N latitude. This city which is located in the center of East Azerbaijan province, has been ruined by terrible earthquakes, which is due to the presence of active faults in the region. Seismic hazard assessment similar to other seismology researches is very complicated due to the effect of different parameters in an earthquake occurring with uncertainty. The amount of uncertainty should be considered in a rational way. The fuzzy method is a suitable method that is used as a decision-making method for solving problems and modeling uncertainties and ambiguities. We used a fuzzy inference system, as the practice is based on uncertainty estimation of seismic hazard for Tabriz region. Peak ground Acceleration value is estimated for fuzzy Logic System in deterministic method 0.55g which is obtained from a seismic source with a Mmax=8.0 at a distance of  36.98 km of Tabriz city.The contour map of the peak ground acceleration throughout Tabriz city can help in urban planning.  }, keywords_fa = {Fuzzy inference system,Seismic hazard,Deterministic Approach,Peak Ground Acceleration,Tabriz,Iran}, url = {https://www.ijgeophysics.ir/article_107051.html}, eprint = {https://www.ijgeophysics.ir/article_107051_848e36fc7bc92e71b45f35562c6e6351.pdf} } @article { author = {Heidari, Reza}, title = {Parametric Criteria in Onsite Earthquake Early Warning System}, journal = {Iranian Journal of Geophysics}, volume = {14}, number = {4}, pages = {29-39}, year = {2020}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {10.30499/ijg.2020.107329}, abstract = {In recent years, rapid estimation of Peak Ground Motion (PGM) and Modified Mercalli Intensity (MMI) based on a few seconds of the initial portion of  wave has been studied as the most important part of the onsite Earthquake Early Warning (EEW) systems studies. To establish an onsite EEW, we need the empirical relationship between earthquake size, PGM and epicentral distance in real-time mode. In some EEWs, the epicentral distance is estimated from the amplitude growth rate of a few seconds of P waves. Many studies have empirically confirmed that the growth rate becomes smaller as epicentral distance becomes far. This relation is true regardless of the earthquake size. In the current study, five parametric criteria including , , ,  and  are proposed for quick detection of destructive oncoming strong motions at a specific target based on ground motions of the first 4 seconds of Japan event waveforms where  and  parameters represent the characteristics of  wave envelope curve in a simple function with the form of . In this study, parameter is inversely proportional to epicentral distance which can be readily estimated within a given short time after P waves’ arrival. ,  and  are the initial peak ground acceleration, velocity and displacement, respectively. The current study represent five thresholds parameters including , , ,  and  in order to warn a Peak Ground Velocity ( ) greater than about 10 cm/sec which are clustered in strong shaking with Modified Mercalli Intensity ( ) larger than . Therefore, destructive earthquakes can be detected form the maximum amplitudes and growth rate of few seconds of P waves by using mentioned parametric criteria.}, keywords = {Onsite earthquake early warnings,KiK-net,P wave,PGV,Parametric criteria}, title_fa = {Parametric Criteria in Onsite Earthquake Early Warning System}, abstract_fa = {In recent years, rapid estimation of Peak Ground Motion (PGM) and Modified Mercalli Intensity (MMI) based on a few seconds of the initial portion of  wave has been studied as the most important part of the onsite Earthquake Early Warning (EEW) systems studies. To establish an onsite EEW, we need the empirical relationship between earthquake size, PGM and epicentral distance in real-time mode. In some EEWs, the epicentral distance is estimated from the amplitude growth rate of a few seconds of P waves. Many studies have empirically confirmed that the growth rate becomes smaller as epicentral distance becomes far. This relation is true regardless of the earthquake size. In the current study, five parametric criteria including , , ,  and  are proposed for quick detection of destructive oncoming strong motions at a specific target based on ground motions of the first 4 seconds of Japan event waveforms where  and  parameters represent the characteristics of  wave envelope curve in a simple function with the form of . In this study, parameter is inversely proportional to epicentral distance which can be readily estimated within a given short time after P waves’ arrival. ,  and  are the initial peak ground acceleration, velocity and displacement, respectively. The current study represent five thresholds parameters including , , ,  and  in order to warn a Peak Ground Velocity ( ) greater than about 10 cm/sec which are clustered in strong shaking with Modified Mercalli Intensity ( ) larger than . Therefore, destructive earthquakes can be detected form the maximum amplitudes and growth rate of few seconds of P waves by using mentioned parametric criteria.}, keywords_fa = {Onsite earthquake early warnings,KiK-net,P wave,PGV,Parametric criteria}, url = {https://www.ijgeophysics.ir/article_107329.html}, eprint = {https://www.ijgeophysics.ir/article_107329_a0718ea7e82f4caa0b5f40999be198ad.pdf} } @article { author = {Shahbazi, Amin and Soleimani monfared, Mehrdad and Thiruchelvam, Vinesh and Ka Fei, Thang}, title = {Presenting an integrated strategy for porosity mapping in a genetic-based seismic inversion framework in a heterogeneous reservoir}, journal = {Iranian Journal of Geophysics}, volume = {14}, number = {4}, pages = {41-65}, year = {2020}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {10.30499/ijg.2020.223648.1261}, abstract = {Seismic reservoir characterization is a state-of-the-art procedure in using various sources of data. Generally, seismic data, due to their low resolution, are randomly used in the final steps of reservoir characterization. However, extensive coverage of 3D seismic data, compared to well data, makes it possible to be applicable for the distribution of characters through the whole reservoir. In this regard, seismic data should be inverted to illustrate the desired characters throughout the media. Conventionally, seismic inversion uses well logs that have defects in its derivation steps, such as wavelet extraction and its propagation through media. The proposed strategy to resolve such deficiencies is the genetic inversion. However, genetic inversion has its own deficiency in accuracy. In this study, we propose an integrated strategy for using various sources of data in an iterative manner for resolving this obstacle. The proposed strategy uses a combined related attribute to evaluate initial acoustic impedance inverted model by genetic inversion. The model then would be updated to satisfy well data. The proposed strategy was applied to a heterogeneous reservoir from the southwest of Iran. Three seismic attributes were integrated to produce a unique attribute for initial model evaluation. The final model was then evaluated by well data. Results were also compared with the conventional method of seismic inversion. The result of the proposed strategy in the genetic inversion depicted improvement in the final acoustic impedance and the porosity distribution model.  }, keywords = {seismic reservoir characterization,Genetic inversion,Seismic attributes,porosity distribution}, title_fa = {Presenting an integrated strategy for porosity mapping in a genetic-based seismic inversion framework in a heterogeneous reservoir}, abstract_fa = {Seismic reservoir characterization is a state-of-the-art procedure in using various sources of data. Generally, seismic data, due to their low resolution, are randomly used in the final steps of reservoir characterization. However, extensive coverage of 3D seismic data, compared to well data, makes it possible to be applicable for the distribution of characters through the whole reservoir. In this regard, seismic data should be inverted to illustrate the desired characters throughout the media. Conventionally, seismic inversion uses well logs that have defects in its derivation steps, such as wavelet extraction and its propagation through media. The proposed strategy to resolve such deficiencies is the genetic inversion. However, genetic inversion has its own deficiency in accuracy. In this study, we propose an integrated strategy for using various sources of data in an iterative manner for resolving this obstacle. The proposed strategy uses a combined related attribute to evaluate initial acoustic impedance inverted model by genetic inversion. The model then would be updated to satisfy well data. The proposed strategy was applied to a heterogeneous reservoir from the southwest of Iran. Three seismic attributes were integrated to produce a unique attribute for initial model evaluation. The final model was then evaluated by well data. Results were also compared with the conventional method of seismic inversion. The result of the proposed strategy in the genetic inversion depicted improvement in the final acoustic impedance and the porosity distribution model.  }, keywords_fa = {seismic reservoir characterization,Genetic inversion,Seismic attributes,porosity distribution}, url = {https://www.ijgeophysics.ir/article_109973.html}, eprint = {https://www.ijgeophysics.ir/article_109973_59f31a4f145ad3303ebe0085624718e2.pdf} } @article { author = {Hashemi, Hosein and Zarabiha, Hanif}, title = {Application of Gustafson-Kessel algorithm in finding seismically co-pattern zones, A case study on Meybod city}, journal = {Iranian Journal of Geophysics}, volume = {14}, number = {4}, pages = {67-77}, year = {2020}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {10.30499/ijg.2020.227165.1263}, abstract = {The current paper deals with a new use of fuzzy logic in the domain of seismic zonation methodologies with a case study in Meybod, Iran. Determining the risk function of an earthquake is an important issue and for the complete solution, the seismic specialist shall necessarily find the soil response and present an appropriate zonation output to the civil engineer. For tackling this problem, a fuzzy clustering method has been applied in acquiring microtremor data more specifically in the city of Meybod. Dataset is divided into four subsets based on its intrinsic complexity by GK fuzzy clustering. Features in this classification practice are including the coordinates, the output dominant frequency of H/V method and the related amplitudes. Euclidian distance matrix norm is constructed to detect hyper ellipsoidal clusters with different orientations (shape and size) in the dataset. The cluster means are then refreshed in an iterative manner so as to identify the uniform seismic answer into the isolated gatherings. We used this method to determine the four divided seismicity regions with different range of frequencies. In addition, various type of soil structures in Meybod city with high and weak risky area have been cleared and can be applied in hazard and earthquake engineering projects. This approach was significantly well matched with clay and silt dominant on soil observed in the boreholes.  Finally zonation maps based on this new method is provided.}, keywords = {seismic microzonation,Fuzzy logic,Fuzzy Clustering,Meybod city,Site Effect}, title_fa = {Application of Gustafson-Kessel algorithm in finding seismically co-pattern zones, A case study on Meybod city}, abstract_fa = {The current paper deals with a new use of fuzzy logic in the domain of seismic zonation methodologies with a case study in Meybod, Iran. Determining the risk function of an earthquake is an important issue and for the complete solution, the seismic specialist shall necessarily find the soil response and present an appropriate zonation output to the civil engineer. For tackling this problem, a fuzzy clustering method has been applied in acquiring microtremor data more specifically in the city of Meybod. Dataset is divided into four subsets based on its intrinsic complexity by GK fuzzy clustering. Features in this classification practice are including the coordinates, the output dominant frequency of H/V method and the related amplitudes. Euclidian distance matrix norm is constructed to detect hyper ellipsoidal clusters with different orientations (shape and size) in the dataset. The cluster means are then refreshed in an iterative manner so as to identify the uniform seismic answer into the isolated gatherings. We used this method to determine the four divided seismicity regions with different range of frequencies. In addition, various type of soil structures in Meybod city with high and weak risky area have been cleared and can be applied in hazard and earthquake engineering projects. This approach was significantly well matched with clay and silt dominant on soil observed in the boreholes.  Finally zonation maps based on this new method is provided.}, keywords_fa = {seismic microzonation,Fuzzy logic,Fuzzy Clustering,Meybod city,Site Effect}, url = {https://www.ijgeophysics.ir/article_110244.html}, eprint = {https://www.ijgeophysics.ir/article_110244_00710a15335b840cc35ca900e13b063b.pdf} } @article { author = {Hessami, Khaled}, title = {Polyphase Inversion Tectonics in Western Alborz Mountains, Northern Iran}, journal = {Iranian Journal of Geophysics}, volume = {14}, number = {4}, pages = {79-88}, year = {2020}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {10.30499/ijg.2020.248614.1291}, abstract = {Fault kinematics in western Alborz mountains is complicated by range-parallel left lateral strike slip faults as well as a series of longitudinal zones of thrusts that are considered to be due to the inversion of pre-existing right lateral and normal faults, respectively. Previously proposed models suggested that the NW component of the motion resulted from the clockwise rotation of the South Caspian block is responsible for left lateral motion on the NW trending faults in western Alborz. However, a more recently proposed model suggests that only if several basement blocks rotate clockwise about vertical axes, the left lateral motion along range-parallel basement faults can occur. Recent GPS studies indicate that northern Iran including north central Iran, Alborz mountains as well as South Caspian block are rotating clockwise with respect to Eurasia. Here, I invoke the previously published evidence to suggest a new tectonic model to explain a sequence of invert deformation episodes as well as the observed structural features and the active deformation in western Alborz mountains. According to this model the western Alborz mountains initiated as several east-west trending extensional (pull-apart) basins associated with left lateral motions on the large-scale strike slip basement faults and intervening normal faulting at least since the Late Triassic time. The inversion of left lateral strike slip faults in Late Cretaceous and Neogene times, however, could be due to a halt in block rotations. In other words, when the blocks stopped rotating the NW trending faults bounding them, they might be affected by the convergence between central Iran and the South Caspian block. This N-S compression would presumably cause dextral motion on the NW trending strike slip basement faults in western Alborz. The resulting dextral motion on the NW strike slip faults, in turn, caused pre-existing normal faults bounding the pull-apart basins to turn into the reverse faults. As rotation of the central Iran-western Alborz-South Caspian blocks resumed first in Eocene and then in the Quaternary times, the NW trending basement faults regained their left lateral motions and the associated east-west basement reverse faults turned into the normal faults. However, geodetically observed shortening across the western Alborz mountains indicates that the east-west reverse faults within the cover unit have remained reverse. This contradiction may be explained by simultaneous shortening of the cover unit resulted from convergence between central Iran and South Caspian block, and extension of the basement due to clockwise rotation of the central Iran-western Alborz-South Caspian blocks.}, keywords = {Inversion tectonics,Alborz,Block rotation,Seismicity,Iran}, title_fa = {Polyphase Inversion Tectonics in Western Alborz Mountains, Northern Iran}, abstract_fa = {Fault kinematics in western Alborz mountains is complicated by range-parallel left lateral strike slip faults as well as a series of longitudinal zones of thrusts that are considered to be due to the inversion of pre-existing right lateral and normal faults, respectively. Previously proposed models suggested that the NW component of the motion resulted from the clockwise rotation of the South Caspian block is responsible for left lateral motion on the NW trending faults in western Alborz. However, a more recently proposed model suggests that only if several basement blocks rotate clockwise about vertical axes, the left lateral motion along range-parallel basement faults can occur. Recent GPS studies indicate that northern Iran including north central Iran, Alborz mountains as well as South Caspian block are rotating clockwise with respect to Eurasia. Here, I invoke the previously published evidence to suggest a new tectonic model to explain a sequence of invert deformation episodes as well as the observed structural features and the active deformation in western Alborz mountains. According to this model the western Alborz mountains initiated as several east-west trending extensional (pull-apart) basins associated with left lateral motions on the large-scale strike slip basement faults and intervening normal faulting at least since the Late Triassic time. The inversion of left lateral strike slip faults in Late Cretaceous and Neogene times, however, could be due to a halt in block rotations. In other words, when the blocks stopped rotating the NW trending faults bounding them, they might be affected by the convergence between central Iran and the South Caspian block. This N-S compression would presumably cause dextral motion on the NW trending strike slip basement faults in western Alborz. The resulting dextral motion on the NW strike slip faults, in turn, caused pre-existing normal faults bounding the pull-apart basins to turn into the reverse faults. As rotation of the central Iran-western Alborz-South Caspian blocks resumed first in Eocene and then in the Quaternary times, the NW trending basement faults regained their left lateral motions and the associated east-west basement reverse faults turned into the normal faults. However, geodetically observed shortening across the western Alborz mountains indicates that the east-west reverse faults within the cover unit have remained reverse. This contradiction may be explained by simultaneous shortening of the cover unit resulted from convergence between central Iran and South Caspian block, and extension of the basement due to clockwise rotation of the central Iran-western Alborz-South Caspian blocks.}, keywords_fa = {Inversion tectonics,Alborz,Block rotation,Seismicity,Iran}, url = {https://www.ijgeophysics.ir/article_118744.html}, eprint = {https://www.ijgeophysics.ir/article_118744_1509edea46f7fbae856b636e8e43571e.pdf} } @article { author = {Hamed, Amir Ali and Moradi, Ali}, title = {On the Diffusivity of Noise Data Recorded (2-8 Hz) at Stations Located in North-Western Iran}, journal = {Iranian Journal of Geophysics}, volume = {14}, number = {4}, pages = {89-99}, year = {2020}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {10.30499/ijg.2020.251816.1294}, abstract = {Since the advent of seismic interferometry, the cross-correlation of received random noises has been very frequently used for the approximate assessment of the empirical Green’s function between the station pairs. Theoretically, the diffusivity of noise wavefield isthe key factor that contributes to the success of this idea in real applications. Diffusivity itself requires the fulfillment of two conditions of energy equipartitioning as well as a homogeneous distribution of the incoming noise. To meet these requirements, the attempts are made to select a longer study period to homogenize the incoming azimuths. This solution is mostly logical in the range of 0.1-0.3 Hz, because it is believed that in this frequency range, microseismic noise waves are received continuously by the stations. But at higher frequencies, seismic sources are mostly changing both spatially and temporally, and their spectral content is not stationary over time. Therefore, in high-frequency seismic interferometry, prolonging the study interval will not help much in improving the signal-to-noise ratio of the retrieved Green’s functions. For this reason, the main focus in such studies is on highly heterogeneous regions because multiple scattering in these regions may be able to azimuthally homogenize the wave field to some extent. According to the scientific studies, however, the homogeneity of the azimuthal distribution of noise is very unlikely to happen, even in the most heterogeneous areas. So to know which claim is more correct, we turned our attention to the northwestern region of Iran, where the severe heterogeneity of the medium for frequencies above 1 Hz has already been confirmed by recent studies. With the help of a Frequency-Dependent Polarization Analysis (FDPA), we first extracted those elliptically polarized waves whose degree of polarization (IDOP) was greater than 0.8. This constraint assures us that the received waves have maintained their coherency for a relatively long time before reaching the station. Our analysis on the azimuths of these polarized data fail to pass Kuaper and  tests, indicating that the azimuth distribution of the received signals at the stations located in north-western Iran is azimuthally inhomogeneous. At the stations near the topography, even strong directivity in coherent seismic noises was observed.   }, keywords = {Seismic noise interferometry,diffusivity,Azimuthal homogeneity}, title_fa = {On the Diffusivity of Noise Data Recorded (2-8 Hz) at Stations Located in North-Western Iran}, abstract_fa = {Since the advent of seismic interferometry, the cross-correlation of received random noises has been very frequently used for the approximate assessment of the empirical Green’s function between the station pairs. Theoretically, the diffusivity of noise wavefield isthe key factor that contributes to the success of this idea in real applications. Diffusivity itself requires the fulfillment of two conditions of energy equipartitioning as well as a homogeneous distribution of the incoming noise. To meet these requirements, the attempts are made to select a longer study period to homogenize the incoming azimuths. This solution is mostly logical in the range of 0.1-0.3 Hz, because it is believed that in this frequency range, microseismic noise waves are received continuously by the stations. But at higher frequencies, seismic sources are mostly changing both spatially and temporally, and their spectral content is not stationary over time. Therefore, in high-frequency seismic interferometry, prolonging the study interval will not help much in improving the signal-to-noise ratio of the retrieved Green’s functions. For this reason, the main focus in such studies is on highly heterogeneous regions because multiple scattering in these regions may be able to azimuthally homogenize the wave field to some extent. According to the scientific studies, however, the homogeneity of the azimuthal distribution of noise is very unlikely to happen, even in the most heterogeneous areas. So to know which claim is more correct, we turned our attention to the northwestern region of Iran, where the severe heterogeneity of the medium for frequencies above 1 Hz has already been confirmed by recent studies. With the help of a Frequency-Dependent Polarization Analysis (FDPA), we first extracted those elliptically polarized waves whose degree of polarization (IDOP) was greater than 0.8. This constraint assures us that the received waves have maintained their coherency for a relatively long time before reaching the station. Our analysis on the azimuths of these polarized data fail to pass Kuaper and  tests, indicating that the azimuth distribution of the received signals at the stations located in north-western Iran is azimuthally inhomogeneous. At the stations near the topography, even strong directivity in coherent seismic noises was observed.   }, keywords_fa = {Seismic noise interferometry,diffusivity,Azimuthal homogeneity}, url = {https://www.ijgeophysics.ir/article_120487.html}, eprint = {https://www.ijgeophysics.ir/article_120487_f820af51084f3b9743080b652f355637.pdf} }