@article { author = {Kalaee, Mohammad Javad and Katoh, Yuto}, title = {The transition energy and the beaming angle of converted LO-mode waves from 100 to 400 kHz through density gradient according to observations of kilometric continuum radiations in the plasmapause}, journal = {Iranian Journal of Geophysics}, volume = {10}, number = {5}, pages = {1-9}, year = {2017}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {The satellite observations such as the Cluster mission with four-point measurements show some local fluctuations in the density gradient in the vicinity of the plasmapause. These structures are found over a broad range of spatial scales, with a size from 20 to 5000 km. Also, the simultaneous observations of the kilometric continuum by IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) and GEOTAIL satellites have indicated another new evidence of a very broad emission. In this study, we considered the mode conversion of waves propagating under the presence of the density gradient in a scale length from 20 to 10,000 km, for a range of frequency from 100 to 400 kHz according to observations of the kilometric continuum. We calculated the transmitted energy flux as a function of the spatial scale lengths and the frequencies. We also calculated the resultant beaming angle for the frequency and the wave normal angle of incident waves. For these cases, results showed that the beaming angle becomes larger and smaller than the angle estimated by Jones’ formula. We suggest that the spatial scale length should be less than about 100 km for the efficient mode conversion and then that the beaming angle becomes consistent with the observed the kilometric continuum.}, keywords = {beaming angle,scale length,Cluster mission,kilometric continuum}, title_fa = {The transition energy and the beaming angle of converted LO-mode waves from 100 to 400 kHz through density gradient according to observations of kilometric continuum radiations in the plasmapause}, abstract_fa = {The satellite observations such as the Cluster mission with four-point measurements show some local fluctuations in the density gradient in the vicinity of the plasmapause. These structures are found over a broad range of spatial scales, with a size from 20 to 5000 km. Also, the simultaneous observations of the kilometric continuum by IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) and GEOTAIL satellites have indicated another new evidence of a very broad emission. In this study, we considered the mode conversion of waves propagating under the presence of the density gradient in a scale length from 20 to 10,000 km, for a range of frequency from 100 to 400 kHz according to observations of the kilometric continuum. We calculated the transmitted energy flux as a function of the spatial scale lengths and the frequencies. We also calculated the resultant beaming angle for the frequency and the wave normal angle of incident waves. For these cases, results showed that the beaming angle becomes larger and smaller than the angle estimated by Jones’ formula. We suggest that the spatial scale length should be less than about 100 km for the efficient mode conversion and then that the beaming angle becomes consistent with the observed the kilometric continuum.}, keywords_fa = {beaming angle,scale length,Cluster mission,kilometric continuum}, url = {https://www.ijgeophysics.ir/article_34126.html}, eprint = {https://www.ijgeophysics.ir/article_34126_88a97f911d01ba37c54b81b8682bac85.pdf} } @article { author = {Jamasb, Ali and Motavalli-Anbaran, Seyed-Hani}, title = {Non-linear stochastic inversion of regional Bouguer anomalies by means of Particle Swarm Optimization: Application to the Zagros Mountains}, journal = {Iranian Journal of Geophysics}, volume = {10}, number = {5}, pages = {10-21}, year = {2017}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {Estimating the lateral depth variations of the Earth’s crust from gravity data is a non-linear ill-posed problem. The ill-posedness of the problem is due to the presence of noise in the data, and also the non-uniqueness of the problem. Particle Swarm Optimization (PSO) is a stochastic population-based optimizer, originally inspired by the social behavior of fish schools and bird flocks. PSO is a global search method, meaning that it has the ability to escape local minima. In addition, PSO is an iterative method, wherein an initial solution is chosen randomly and then improved iteratively until the algorithm finds a solution close enough to the global minimum. Herein, the inverse problem of estimating the thickness of the crust from gravity anomalies is formulated as a single objective optimization problem and is solved by PSO. The method is first tested on a realistic synthetic crustal model both with and without the presence of white Gaussian noise (WGN). Then it is applied to the gravity data from EIGEN-6c4, the latest combined global gravity model, in order to find the base of the crust in the Zagros Mountains (Iran) and compare the results with those of other geophysical methods. The assumed crustal model is one with a linear density gradient in which the densities at both the surface and the base of the crust are fixed. Results agree well with the previously published works including both seismic and potential field studies.}, keywords = {gravity data,Particle Swarm Optimization (PSO),Zagros mountains}, title_fa = {Non-linear stochastic inversion of regional Bouguer anomalies by means of Particle Swarm Optimization: Application to the Zagros Mountains}, abstract_fa = {Estimating the lateral depth variations of the Earth’s crust from gravity data is a non-linear ill-posed problem. The ill-posedness of the problem is due to the presence of noise in the data, and also the non-uniqueness of the problem. Particle Swarm Optimization (PSO) is a stochastic population-based optimizer, originally inspired by the social behavior of fish schools and bird flocks. PSO is a global search method, meaning that it has the ability to escape local minima. In addition, PSO is an iterative method, wherein an initial solution is chosen randomly and then improved iteratively until the algorithm finds a solution close enough to the global minimum. Herein, the inverse problem of estimating the thickness of the crust from gravity anomalies is formulated as a single objective optimization problem and is solved by PSO. The method is first tested on a realistic synthetic crustal model both with and without the presence of white Gaussian noise (WGN). Then it is applied to the gravity data from EIGEN-6c4, the latest combined global gravity model, in order to find the base of the crust in the Zagros Mountains (Iran) and compare the results with those of other geophysical methods. The assumed crustal model is one with a linear density gradient in which the densities at both the surface and the base of the crust are fixed. Results agree well with the previously published works including both seismic and potential field studies.  }, keywords_fa = {gravity data,Particle Swarm Optimization (PSO),Zagros mountains}, url = {https://www.ijgeophysics.ir/article_42516.html}, eprint = {https://www.ijgeophysics.ir/article_42516_eb860151f1037168175d5f5ffa88f544.pdf} } @article { author = {Moghaddam, Sadegh and Kamkar Rouhani, Abolghasem and Arab Amiri, Alireza}, title = {Subsurface structural characterization of the Chooman Dam site using geoelectric method}, journal = {Iranian Journal of Geophysics}, volume = {10}, number = {5}, pages = {22-30}, year = {2017}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {A recent evaluation of Chooman Dam highlighted the potential for dam failure due to either seepage or an earthquake on nearby faults. Unfortunately, this dam suffers from infiltration or leakage problems related mainly to different geological and tectonic factors. In response to these concerns, electrical resistivity surveys employing vertical electric sounding (VES) method were carried out at the dam site, located in Kurdistan Province in the west of Iran in order to delineate potential pathways of leakage occurring thorough the subsurface structure close to the dam body, bed rock depth and lateral discontinuities in the study area. The VES surveys were conducted using the Schlumberger electrode array in 400 points or stations along 28 profiles at a station interval of 20 to 50 m in up- and downstream sides of the dam embankment. For data acquisition, a terrameter SAS 4000 resistivity system, made by Swedish ABEM Company, was used. Maximum separation of current electrodes in the Schlumberger VES surveys was considered 430 m. These geoelectrical studies revealed a thick package of andesite basement in the eastern part and vitriform tuff basement in the western part of the study area. Considering the results and the detection of a strike-slip fault on the downstream side of the dam embankment, it is evident that fractures are the main causative factor responsible for the leakage in the Chooman Dam.}, keywords = {Electrical resistivity,vertical electric sounding (VES) method,Schlumberger array,Chooman Dam,Kurdistan province,Iran}, title_fa = {Subsurface structural characterization of the Chooman Dam site using geoelectric method}, abstract_fa = {A recent evaluation of Chooman Dam highlighted the potential for dam failure due to either seepage or an earthquake on nearby faults. Unfortunately, this dam suffers from infiltration or leakage problems related mainly to different geological and tectonic factors. In response to these concerns, electrical resistivity surveys employing vertical electric sounding (VES) method were carried out at the dam site, located in Kurdistan Province in the west of Iran in order to delineate potential pathways of leakage occurring thorough the subsurface structure close to the dam body, bed rock depth and lateral discontinuities in the study area. The VES surveys were conducted using the Schlumberger electrode array in 400 points or stations along 28 profiles at a station interval of 20 to 50 m in up- and downstream sides of the dam embankment. For data acquisition, a terrameter SAS 4000 resistivity system, made by Swedish ABEM Company, was used. Maximum separation of current electrodes in the Schlumberger VES surveys was considered 430 m. These geoelectrical studies revealed a thick package of andesite basement in the eastern part and vitriform tuff basement in the western part of the study area. Considering the results and the detection of a strike-slip fault on the downstream side of the dam embankment, it is evident that fractures are the main causative factor responsible for the leakage in the Chooman Dam.}, keywords_fa = {Electrical resistivity,vertical electric sounding (VES) method,Schlumberger array,Chooman Dam,Kurdistan province,Iran}, url = {https://www.ijgeophysics.ir/article_46953.html}, eprint = {https://www.ijgeophysics.ir/article_46953_8bd0683c1ffed5e14909d31deb675d26.pdf} } @article { author = {Farzaneh, Saeed and Sharifi, Mohammad Ali}, title = {The regional estimates of the GPS satellite and receiver differential code biases}, journal = {Iranian Journal of Geophysics}, volume = {10}, number = {5}, pages = {31-41}, year = {2017}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {The Differential Code Biases (DCB), which are also termed hardware delay biases, are the frequency-dependent time delays of the satellite and receiver. Possible sources of these delays are antennas and cables, as well as different filters used in receivers and satellites. These instrumental delays affect both code and carrier measurements. These biases for satellites and some IGS stations tend to be obtained from the Center for Orbit Determination in Europe (CODE) as daily or monthly constants, which are based on the global ionospheric total electron content (TEC) modeling in the solar-geomagnetic frame. These biases are not provided for regional and local network receivers, and need to be computed by the user. In this study, the regional approach by the spherical Slepian function was used to estimate the GPS satellite and receiver DCBs. Validations using real data showed that this method has significant potential and the ability to yield reliable results, even for a single station DCB estimate.}, keywords = {DCB,GPS,Slepian function,regional modeling}, title_fa = {The regional estimates of the GPS satellite and receiver differential code biases}, abstract_fa = {The Differential Code Biases (DCB), which are also termed hardware delay biases, are the frequency-dependent time delays of the satellite and receiver. Possible sources of these delays are antennas and cables, as well as different filters used in receivers and satellites. These instrumental delays affect both code and carrier measurements. These biases for satellites and some IGS stations tend to be obtained from the Center for Orbit Determination in Europe (CODE) as daily or monthly constants, which are based on the global ionospheric total electron content (TEC) modeling in the solar-geomagnetic frame. These biases are not provided for regional and local network receivers, and need to be computed by the user. In this study, the regional approach by the spherical Slepian function was used to estimate the GPS satellite and receiver DCBs. Validations using real data showed that this method has significant potential and the ability to yield reliable results, even for a single station DCB estimate.}, keywords_fa = {DCB,GPS,Slepian function,regional modeling}, url = {https://www.ijgeophysics.ir/article_46954.html}, eprint = {https://www.ijgeophysics.ir/article_46954_b221322f44a3ad82da67c3d89f374beb.pdf} } @article { author = {Pahlavanloo, Ali and Soleimani monfared, Mehrdad and Gallo, Claudio}, title = {Improving seismic image in complex structures by new solving strategies in the CO-CRS and the CO-CDS methods}, journal = {Iranian Journal of Geophysics}, volume = {10}, number = {5}, pages = {42-56}, year = {2017}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {Conventional seismic imaging possesses problem in exposing structural detail in complex geological media. Nevertheless, some recently introduced methods reduce this ambiguity to some extent, by using data based imaging operator or emancipation from the macro-velocity model. The zero offset common reflection surface (ZO-CRS) stack method is a velocity independent imaging technique which is frequently used in seismic imaging. Various modifications of this method were introduced through its development. The ZO diffraction stacking operator, the common offset CRS (CO-CRS) and anisotropic CRS methods were introduced to enhance the final seismic image. As diffraction events are carriers of structural details information, we adhere to improve response diffraction to obtain more structural details in the final image. Thus we combined advantages of the CO-CRS method by the diffraction operator to make the CO-CDS stack operator. The parameters of the reflection operator were changed to fulfill conditions of a diffraction response in CO domain. Meanwhile, to resolve the problem of conflicting dips, the solving strategy was modified in order to consider all possible angles and make a contribution to them in their related operators. Thus it was expected that the CO-CDS stack reveals weak diffraction events in the stacked section, in favor of further depth migration. The introduced method was applied to a synthetic and land data. Utilizing the CO-CDS method on the synthetic data brings out as much as diffraction in the stacked result. For land data set, the CO-CDS operator boosted the share of diffraction in the stack section which was further underwent depth migration procedure by the robust Gaussian Beam algorithm with a smooth velocity model. Outstanding enhancement in the final result compared to the conventional and the CRS methods were depicted by depth imaging of the CO-CDS result, which was a consequence of improved diffraction based operator of the CRS method.}, keywords = {seismic imaging,CRS,CDS,diffraction imaging,Gaussian Beam migration}, title_fa = {Improving seismic image in complex structures by new solving strategies in the CO-CRS and the CO-CDS methods}, abstract_fa = {Conventional seismic imaging possesses problem in exposing structural detail in complex geological media. Nevertheless, some recently introduced methods reduce this ambiguity to some extent, by using data based imaging operator or emancipation from the macro-velocity model. The zero offset common reflection surface (ZO-CRS) stack method is a velocity independent imaging technique which is frequently used in seismic imaging. Various modifications of this method were introduced through its development. The ZO diffraction stacking operator, the common offset CRS (CO-CRS) and anisotropic CRS methods were introduced to enhance the final seismic image. As diffraction events are carriers of structural details information, we adhere to improve response diffraction to obtain more structural details in the final image. Thus we combined advantages of the CO-CRS method by the diffraction operator to make the CO-CDS stack operator. The parameters of the reflection operator were changed to fulfill conditions of a diffraction response in CO domain. Meanwhile, to resolve the problem of conflicting dips, the solving strategy was modified in order to consider all possible angles and make a contribution to them in their related operators. Thus it was expected that the CO-CDS stack reveals weak diffraction events in the stacked section, in favor of further depth migration. The introduced method was applied to a synthetic and land data. Utilizing the CO-CDS method on the synthetic data brings out as much as diffraction in the stacked result. For land data set, the CO-CDS operator boosted the share of diffraction in the stack section which was further underwent depth migration procedure by the robust Gaussian Beam algorithm with a smooth velocity model. Outstanding enhancement in the final result compared to the conventional and the CRS methods were depicted by depth imaging of the CO-CDS result, which was a consequence of improved diffraction based operator of the CRS method.}, keywords_fa = {seismic imaging,CRS,CDS,diffraction imaging,Gaussian Beam migration}, url = {https://www.ijgeophysics.ir/article_46955.html}, eprint = {https://www.ijgeophysics.ir/article_46955_561625d290b9d4c93ca559e35d356b61.pdf} } @article { author = {Khandan, Reza and Alavipanah, Seyed Kazem and Pour Biazar, Arastoo and Gharaylou, Maryam}, title = {Analysis of updraft velocity in mesoscale convective systems using satellite and WRF model simulations}, journal = {Iranian Journal of Geophysics}, volume = {10}, number = {5}, pages = {57-70}, year = {2017}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {Updraft vertical velocity is an important dynamical quantity which is strongly related to storm intensity and heavy precipitation. It can be calculated by direct observations, NWP model, and geostationary satellites which can provide the possibility of measuring this quantity with high temporal resolution. This research analyzed updraft velocity based on six derived parameters from INSAT3-D and high temporal and spatial resolution simulations of WRF model in the west and southwest of Iran. The interrelationship among the derived variables was investigated from the immature to mature stages of convective cells in Mesoscale Convective Systems (MCS). Updraft velocity was calculated based on a theoretical framework and real observations. The was a large results discrepancy among the results. This finding was in company with previous studies which concluded that updraft velocity is the resultant of other bulk buoyancy forces and environmental variables. Also, the estimated updraft velocities showed a positive correlation with height. The authors proposed linear regression, as a parametric, and Random Forest (RF), as a non-parametric, machine learning methods for estimation of updraft velocity based on satellite variables. A forward–backward method was applied to reach the best modeling in both methods. In linear regression modeling, the cloud-top cooling rate was the most significant factor, and in the RF, band difference of water vapor, thermal infrared 1, and elevation data had the maximum importance. Results showed that the RF could better estimate updraft velocity.}, keywords = {MCS,updraft velocity,NWP,geostationary satellite,CAPE}, title_fa = {Analysis of updraft velocity in mesoscale convective systems using satellite and WRF model simulations}, abstract_fa = {Updraft vertical velocity is an important dynamical quantity which is strongly related to storm intensity and heavy precipitation. It can be calculated by direct observations, NWP model, and geostationary satellites which can provide the possibility of measuring this quantity with high temporal resolution. This research analyzed updraft velocity based on six derived parameters from INSAT3-D and high temporal and spatial resolution simulations of WRF model in the west and southwest of Iran. The interrelationship among the derived variables was investigated from the immature to mature stages of convective cells in Mesoscale Convective Systems (MCS). Updraft velocity was calculated based on a theoretical framework and real observations. The was a large results discrepancy among the results. This finding was in company with previous studies which concluded that updraft velocity is the resultant of other bulk buoyancy forces and environmental variables. Also, the estimated updraft velocities showed a positive correlation with height. The authors proposed linear regression, as a parametric, and Random Forest (RF), as a non-parametric, machine learning methods for estimation of updraft velocity based on satellite variables. A forward–backward method was applied to reach the best modeling in both methods. In linear regression modeling, the cloud-top cooling rate was the most significant factor, and in the RF, band difference of water vapor, thermal infrared 1, and elevation data had the maximum importance. Results showed that the RF could better estimate updraft velocity.}, keywords_fa = {MCS,updraft velocity,NWP,geostationary satellite,CAPE}, url = {https://www.ijgeophysics.ir/article_46956.html}, eprint = {https://www.ijgeophysics.ir/article_46956_90a76c7f9dcd03ce76c2e2fa42df4829.pdf} } @article { author = {Saberi, Mohammad Reza}, title = {A closer look at rock physics models and their assisted interpretation in seismic exploration}, journal = {Iranian Journal of Geophysics}, volume = {10}, number = {5}, pages = {71-84}, year = {2017}, publisher = {Iranian Geophysical Society}, issn = {2008-0336}, eissn = {2783-168X}, doi = {}, abstract = {Subsurface rocks and their fluid content along with their architecture affect reflected seismic waves through variations in their travel time, reflection amplitude, and phase within the field of exploration seismology. The combined effects of these factors make subsurface interpretation by using reflection waves very difficult. Therefore, assistance from other subsurface disciplines is needed if we intend to make a more accurate image of the subsurface. In this regard, rock physics acts as an integrated tool to combine subsurface information from different disciplines in a set of relationships between engineering (petrophysical) properties and their relevant geophysical variations, or more specifically, elastic variations. As a matter of fact, rock physics is required for a better understanding of rock properties if we intend to have a full understanding of our reservoir properties and their fluid content. This paper reviews some of the most important rock physics models and their application within the field of seismic exploration. These models are generally valid for the given conditions in which they are derived, and as a result, having a good understanding of their physical and geological limitations can help a lot with accurate rock physics modeling and interpretation. In this regard, this paper is an attempt to create a better understanding of such models, using different references and my personal experiences with these models. The application contexts of the models presented in this paper are not limited to the discussed scenarios. These scenarios are the ones that are commonly used and have shown a good prediction power in practice.}, keywords = {Rock Physics,seismic velocities,elastic rock properties,rock properties,exploration seismology}, title_fa = {A closer look at rock physics models and their assisted interpretation in seismic exploration}, abstract_fa = {Subsurface rocks and their fluid content along with their architecture affect reflected seismic waves through variations in their travel time, reflection amplitude, and phase within the field of exploration seismology. The combined effects of these factors make subsurface interpretation by using reflection waves very difficult. Therefore, assistance from other subsurface disciplines is needed if we intend to make a more accurate image of the subsurface. In this regard, rock physics acts as an integrated tool to combine subsurface information from different disciplines in a set of relationships between engineering (petrophysical) properties and their relevant geophysical variations, or more specifically, elastic variations. As a matter of fact, rock physics is required for a better understanding of rock properties if we intend to have a full understanding of our reservoir properties and their fluid content. This paper reviews some of the most important rock physics models and their application within the field of seismic exploration. These models are generally valid for the given conditions in which they are derived, and as a result, having a good understanding of their physical and geological limitations can help a lot with accurate rock physics modeling and interpretation. In this regard, this paper is an attempt to create a better understanding of such models, using different references and my personal experiences with these models. The application contexts of the models presented in this paper are not limited to the discussed scenarios. These scenarios are the ones that are commonly used and have shown a good prediction power in practice.}, keywords_fa = {Rock Physics,seismic velocities,elastic rock properties,rock properties,exploration seismology}, url = {https://www.ijgeophysics.ir/article_46957.html}, eprint = {https://www.ijgeophysics.ir/article_46957_a3a1f00530313478c4d0865bf3125525.pdf} }