انجمن ملی ژئوفیزیک ایرانمجله ژئوفیزیک ایران2008-033618620250120Qualitative and quantitative interpretation of high-resolution gravity data of Ewekoro, Southwest Nigeria using source parameter imaging and Euler deconvolution techniquesQualitative and quantitative interpretation of high-resolution gravity data of Ewekoro, Southwest Nigeria using source parameter imaging and Euler deconvolution techniques11618580510.30499/ijg.2023.398619.1533FAGideon OluyinkaLayadeAssociate Professor, Department of Physics, (Geophysics Unit), Federal University of Agriculture, Abeokuta, Nigeria0000-0002-3665-6883Emmanuel OluwatoyinBamideleM.Sc. Graduate, Department of Physics, Federal University of Agriculture Abeokuta, NigeriaVictorMakindeProfessor, Department of Physics, (Geophysics Unit) Federal University of Agriculture Abeokuta, NigeriaBabatunde SaheedBadaProfessor, Department of Environmental Management & Toxicology, Federal University of Agriculture Abeokuta, NigeriaHazeen OwolabiEdunjobiLecturer, Department of Physics, Sikiru Adetona College of Education, Science and Technology, Omu-Ajose, Nigeria0000-0003-0129-3389Journal Article20230731Geoscientists are interested in investigating the subsurface mineral resources such as crude oil through exploration of the Earth's subsurface. The availability and extent of these important commercial minerals can be ascertained by the characteristics of their geophysical properties through a geophysical survey in the area under investigation. Gravity method is a non-destructive geophysical method primarily used for locating the presence of solid minerals. This research work is aimed at using data coordinate interpolation techniques to extract information from aerogravity data obtained over Ewekoro in order to estimate the depth of the overburden thickness of the geological contact of the observed causative potential field anomaly. Hence, Source Parameter Imaging (SPI) and Euler deconvolution methods were applied on airborne gravity data of Ewekoro in both qualitative and quantitative approaches. The airborne gravity data sheets 260 and 279 acquired by the Bureau Gravimetrique International (BGI), through the Earth Gravity Model (EGM08) in 2008 were used. The raw gravity data recorded in digital format of X, Y and Z representing latitude, longitude and the Bouguer gravity values, respectively, were exported into Oasis Montaj software for qualitative and quantitative analysis. The datasets were gridded using the minimum curvature algorithm. Regional-residual separation was carried out to remove low frequency anomalies from the total field by applying a high-pass filter in sharpening the edges of the anomaly and enhancement. A Two-Dimensional Fast Fourier Transform (2D FFT) filtering technique was used in computing different derivative grids. The interpolated gravity map revealed a decrease in anomaly from SW to NE of the study area, with an anomaly range of 15–19 mGal. The SPI revealed a depth range of 235–698 m with the deeper gravity source concentrated in the central region and shallower source discovered in the SE of the study area. The 3D Euler depth estimates corresponding to Structural Index (SI) = 0 applied to the gravity data revealed a depth range of 132–692 m with a scattered Euler solution trending in NW, NE and SSE of the study area. The results for both methods indicate an average correlation in terms of their depths. The investigation revealed Bouguer anomaly thickness of Ewekoro trends in the SW–NE with significant depth for mineral exploration. The heterogeneity of the subsurface of the study area and the overburden thickness of Ewekoro trending in the NNE–NNW with an appreciable depth to harbour mineral resources were established.Geoscientists are interested in investigating the subsurface mineral resources such as crude oil through exploration of the Earth's subsurface. The availability and extent of these important commercial minerals can be ascertained by the characteristics of their geophysical properties through a geophysical survey in the area under investigation. Gravity method is a non-destructive geophysical method primarily used for locating the presence of solid minerals. This research work is aimed at using data coordinate interpolation techniques to extract information from aerogravity data obtained over Ewekoro in order to estimate the depth of the overburden thickness of the geological contact of the observed causative potential field anomaly. Hence, Source Parameter Imaging (SPI) and Euler deconvolution methods were applied on airborne gravity data of Ewekoro in both qualitative and quantitative approaches. The airborne gravity data sheets 260 and 279 acquired by the Bureau Gravimetrique International (BGI), through the Earth Gravity Model (EGM08) in 2008 were used. The raw gravity data recorded in digital format of X, Y and Z representing latitude, longitude and the Bouguer gravity values, respectively, were exported into Oasis Montaj software for qualitative and quantitative analysis. The datasets were gridded using the minimum curvature algorithm. Regional-residual separation was carried out to remove low frequency anomalies from the total field by applying a high-pass filter in sharpening the edges of the anomaly and enhancement. A Two-Dimensional Fast Fourier Transform (2D FFT) filtering technique was used in computing different derivative grids. The interpolated gravity map revealed a decrease in anomaly from SW to NE of the study area, with an anomaly range of 15–19 mGal. The SPI revealed a depth range of 235–698 m with the deeper gravity source concentrated in the central region and shallower source discovered in the SE of the study area. The 3D Euler depth estimates corresponding to Structural Index (SI) = 0 applied to the gravity data revealed a depth range of 132–692 m with a scattered Euler solution trending in NW, NE and SSE of the study area. The results for both methods indicate an average correlation in terms of their depths. The investigation revealed Bouguer anomaly thickness of Ewekoro trends in the SW–NE with significant depth for mineral exploration. The heterogeneity of the subsurface of the study area and the overburden thickness of Ewekoro trending in the NNE–NNW with an appreciable depth to harbour mineral resources were established.
https://www.ijgeophysics.ir/article_185805_c9da4a3a3c5e1d09791a46d0bf0950aa.pdfانجمن ملی ژئوفیزیک ایرانمجله ژئوفیزیک ایران2008-033618620250120Investigating the effect of thermal loading on geothermal piles in stratified soilsInvestigating the effect of thermal loading on geothermal piles in stratified soils172818763210.30499/ijg.2024.423290.1549FAMasoudAmelsakhiAssistant Professor, Department of Civil Engineering, Faculty of Engineering, Qom University of Technology, Qom, Iran0000-0002-5894-0404FatemehSheshpariMaster of Civil Engineering, Department of Civil Engineering, Faculty of Engineering, Qom University of Technology, Qom, IranJournal Article20231101Energy pile is a type of foundation that simultaneously provides the two goals of structural load transfer and energy conversion. In addition to transferring the structural load of the building to the lower layers, this system also acts as a heat exchanger. In this article, to investigate the effect of soil and geothermal pile on each other, numerical modeling was performed using finite element method using COMSOL software. The main purpose of this study is to investigate the response of geothermal pile in layered soils and compare it with geothermal pile implemented in homogeneous soil. This problem has been performed considering the different soil layers that are on the bedrock and the results have been compared with the experimental data of the geothermal pile placed in the layered soil. The results showed that the properties of soils and the location of loose and dense <br />layers in the depth of the soil have a significant effect on the type of behavior of the pile, so the deformations and stresses obtained from the numerical analyzes are related to the modulus of <br />elasticity and in other words, to the hardness of the soil. It conducted that the value of the strain obtained from the numerical analysis of the pile placed in multi-layered soil is between the value of the pile strains in the case where the homogeneous soil is only loose or dense. The conclusion of obtained results is that the vertical stresses and strains of the pile placed in multi-layered soil at the depth of the earth's surface are in better agreement with the vertical stresses and strains of the pile placed in loose soil. The modulus of elasticity of soil with average density of type 2 is 74% higher than the modulus of elasticity of loose soil considered in the analysis, which has led to a 27% <br />reduction in displacement, a 40% increase in compressive stress and a 77% reduction in vertical strain. The same change in the modulus of elasticity of the soil layers caused a change in the values of stresses and pile stresses in the state of layered soil. Also, the 40% change in the modulus of elasticity of type 2 and 3 soils has caused the amount of displacement to decrease by 17% and the amount of compressive stress and strain to increase by 11% and decrease by 27%, respectively. The results of the numerical analysis showed that the type of soil and the way it is located in the depth have a significant effect on the behavior of the geothermal pile.
Energy pile is a type of foundation that simultaneously provides the two goals of structural load transfer and energy conversion. In addition to transferring the structural load of the building to the lower layers, this system also acts as a heat exchanger. In this article, to investigate the effect of soil and geothermal pile on each other, numerical modeling was performed using finite element method using COMSOL software. The main purpose of this study is to investigate the response of geothermal pile in layered soils and compare it with geothermal pile implemented in homogeneous soil. This problem has been performed considering the different soil layers that are on the bedrock and the results have been compared with the experimental data of the geothermal pile placed in the layered soil. The results showed that the properties of soils and the location of loose and dense <br />layers in the depth of the soil have a significant effect on the type of behavior of the pile, so the deformations and stresses obtained from the numerical analyzes are related to the modulus of <br />elasticity and in other words, to the hardness of the soil. It conducted that the value of the strain obtained from the numerical analysis of the pile placed in multi-layered soil is between the value of the pile strains in the case where the homogeneous soil is only loose or dense. The conclusion of obtained results is that the vertical stresses and strains of the pile placed in multi-layered soil at the depth of the earth's surface are in better agreement with the vertical stresses and strains of the pile placed in loose soil. The modulus of elasticity of soil with average density of type 2 is 74% higher than the modulus of elasticity of loose soil considered in the analysis, which has led to a 27% <br />reduction in displacement, a 40% increase in compressive stress and a 77% reduction in vertical strain. The same change in the modulus of elasticity of the soil layers caused a change in the values of stresses and pile stresses in the state of layered soil. Also, the 40% change in the modulus of elasticity of type 2 and 3 soils has caused the amount of displacement to decrease by 17% and the amount of compressive stress and strain to increase by 11% and decrease by 27%, respectively. The results of the numerical analysis showed that the type of soil and the way it is located in the depth have a significant effect on the behavior of the geothermal pile.
https://www.ijgeophysics.ir/article_187632_ef213b02e9a3ac87964e8a3610dad97a.pdfانجمن ملی ژئوفیزیک ایرانمجله ژئوفیزیک ایران2008-033618620250120Investigating the effect of height difference correction between reanalysis grid points and observation stations on the accuracy of ERA5 2m temperature and pressure dataInvestigating the effect of height difference correction between reanalysis grid points and observation stations on the accuracy of ERA5 2m temperature and pressure data294518337610.30499/ijg.2023.414550.1536FAAliSam KhanianiAssistant Professor, Babol Noshirvani University of Technology, Civil Engineering Department, Mazandaran, IranAtefehMohammadiPh.D., Atmospheric Science and Meteorological Research Center (ASMERC), Tehran, IranJournal Article20230902Temperature and surface pressure are among the critical variables in various meteorological and climatic applications. Reanalysis products have become valuable sources of temperature and pressure data in recent years and have garnered much attention. Due to the elevation difference between reanalysis grid points and ground stations, surface pressure and 2m temperature derived from reanalysis products exhibit noticeable biases. In this study, using 10 years of measured data from 202 synoptic stations in Iran, the impact of elevation correction on the accuracy of ERA5 Land (ERA5L) pressure and 2m temperature data was investigated. Three different models were used for elevation correction. A comparison of error statistics before and after elevation correction revealed that in most stations the accuracy of ERA5L temperature and pressure data are improved after elevation correction. The results indicate that after data calibration, the average bias and Root Mean Square Error (RMSE) of surface pressure in the region improved by 96% and 66%, respectively. Compared to surface pressure, the positive impact of elevation correction on ERA5L temperature was less pronounced, with average bias and RMSE improving by 68% and 13%, respectively. Furthermore, for the elevation calibration of ERA5L pressure, the three used models were compared. A comparison of error statistics across all stations demonstrated that the performance of the three models did not show significant differences in the Iran region.Temperature and surface pressure are among the critical variables in various meteorological and climatic applications. Reanalysis products have become valuable sources of temperature and pressure data in recent years and have garnered much attention. Due to the elevation difference between reanalysis grid points and ground stations, surface pressure and 2m temperature derived from reanalysis products exhibit noticeable biases. In this study, using 10 years of measured data from 202 synoptic stations in Iran, the impact of elevation correction on the accuracy of ERA5 Land (ERA5L) pressure and 2m temperature data was investigated. Three different models were used for elevation correction. A comparison of error statistics before and after elevation correction revealed that in most stations the accuracy of ERA5L temperature and pressure data are improved after elevation correction. The results indicate that after data calibration, the average bias and Root Mean Square Error (RMSE) of surface pressure in the region improved by 96% and 66%, respectively. Compared to surface pressure, the positive impact of elevation correction on ERA5L temperature was less pronounced, with average bias and RMSE improving by 68% and 13%, respectively. Furthermore, for the elevation calibration of ERA5L pressure, the three used models were compared. A comparison of error statistics across all stations demonstrated that the performance of the three models did not show significant differences in the Iran region.https://www.ijgeophysics.ir/article_183376_46c133db0e97e519e14826d9c7a9e6f4.pdfانجمن ملی ژئوفیزیک ایرانمجله ژئوفیزیک ایران2008-033618620250120Evaluation of the groundwater potential of Ogbomoso, Southwestern Nigeria, using an adaptive neuro-fuzzy inference system optimized by three metaheuristic algorithmsEvaluation of the groundwater potential of Ogbomoso, Southwestern Nigeria, using an adaptive neuro-fuzzy inference system optimized by three metaheuristic algorithms477819375610.30499/ijg.2024.431927.1559FAPelumi TimothyFajemiloM.Sc. Graduate, Department of Applied Geophysics, Federal University of Technology, Akure, NigeriaKesyton OyamendaOzeginPh.D. , Department of Physics, Ambrose Alli University Ekpoma, Edo State, Nigeria0000-0001-5788-1142Journal Article20231223Groundwater is a significant driver of water supply considering its constant accessibility, intrinsic quality, and ease of immediate diversion to disadvantaged areas. The bulk of the Ogbomoso population relies on surface water because of normative groundwater investigation, which is a laborious and resource-intensive process. Over the last decade, the use of an adaptive neuro-fuzzy inference system (ANFIS) has garnered enthusiastic acceptance in a variety of research domains. This study aimed to evaluate groundwater potential in Ogbomoso, Nigeria, using ANFIS in a geographic information system coupled with three metaheuristic optimizing algorithms: the genetic algorithm (GA), particle swarm optimization (PSO), and the firefly algorithm (FA). To facilitate groundwater potential mapping (GPM) in the research area, a database of 165 wells with 8 predictive parameters was created. Thirty percent (49) of the 165 well locations were designated for the validation set, while the remaining seventy percent (116) were designated for the training set. The slope, lineament density, lithology, overburden thickness, bedrock relief, coefficient of anisotropy, hydraulic conductivity, and transmissivity were the eight groundwater variable parameters generated for modeling. The findings showed that each of the models had good prediction capability; nonetheless, the ANFIS-GA has the strongest predicting effectiveness with a correlation level of r = 0.8 (80%), followed by both the ANFIS-PSO and the ANFIS-FA with r = 0.77 (77%). The groundwater potential index developed for the study region was zoned into low (0.77–1.63) (30%), moderate (1.63–1.74) (25%), and high (1.74–2.50) (45%) using the ANFIS improved by the GA method. The linear correlation method was used to validate the model using 110 water columns from wells in the study area. The findings of this study demonstrate that ANFIS models paired with metaheuristic algorithmic optimization can be an invaluable tool for making decisions for groundwater utilization and monitoring.Groundwater is a significant driver of water supply considering its constant accessibility, intrinsic quality, and ease of immediate diversion to disadvantaged areas. The bulk of the Ogbomoso population relies on surface water because of normative groundwater investigation, which is a laborious and resource-intensive process. Over the last decade, the use of an adaptive neuro-fuzzy inference system (ANFIS) has garnered enthusiastic acceptance in a variety of research domains. This study aimed to evaluate groundwater potential in Ogbomoso, Nigeria, using ANFIS in a geographic information system coupled with three metaheuristic optimizing algorithms: the genetic algorithm (GA), particle swarm optimization (PSO), and the firefly algorithm (FA). To facilitate groundwater potential mapping (GPM) in the research area, a database of 165 wells with 8 predictive parameters was created. Thirty percent (49) of the 165 well locations were designated for the validation set, while the remaining seventy percent (116) were designated for the training set. The slope, lineament density, lithology, overburden thickness, bedrock relief, coefficient of anisotropy, hydraulic conductivity, and transmissivity were the eight groundwater variable parameters generated for modeling. The findings showed that each of the models had good prediction capability; nonetheless, the ANFIS-GA has the strongest predicting effectiveness with a correlation level of r = 0.8 (80%), followed by both the ANFIS-PSO and the ANFIS-FA with r = 0.77 (77%). The groundwater potential index developed for the study region was zoned into low (0.77–1.63) (30%), moderate (1.63–1.74) (25%), and high (1.74–2.50) (45%) using the ANFIS improved by the GA method. The linear correlation method was used to validate the model using 110 water columns from wells in the study area. The findings of this study demonstrate that ANFIS models paired with metaheuristic algorithmic optimization can be an invaluable tool for making decisions for groundwater utilization and monitoring.https://www.ijgeophysics.ir/article_193756_59200fed5dc1a1db8c557735386b46a6.pdfانجمن ملی ژئوفیزیک ایرانمجله ژئوفیزیک ایران2008-033618620250120Application of the ground penetrating radar for detecting the subsurface
cavities-a case study from the Kariz galleriesApplication of the ground penetrating radar for detecting the subsurface cavities-a case study from the Kariz galleries799419437610.30499/ijg.2024.416448.1539FASajjadGhanbariAssistant Professor, Physics Department, Faculty of Sciences, Razi university, Kermanshah, IranAladinEbrahimiPh.D., Department of Computer Science and Information Technology, La Trobe University, Melbourne, AustraliaMohammad KazemHafiziProfessor, Institute of Geophysics, University of Tehran, IranMaksimBanoAssociate Professor, Ecole et observatoire Université de Strasbourg, Strasbourg, FranceNasrinFaramarziM.Sc. Graduate, Razi university, Kermanshah, IranJournal Article20230915In general, a quantitative analysis of ground-penetrating radar (GPR) data provides insights into the depth of sources and underlying geological features. This study compares the depth information obtained from GPR waves using diverse approaches to detect underground cavities. The processing techniques, including conventional processing (Kirchhoff migration), time reversal (TR) imaging, and the application of continuous wavelet transform (CWT) in TR imaging, known as compensated time reversal (CTR), are evaluated in comparison to commercial software. The predicted depths from TR and CTR align closely with drilling results, while traditional processing and Kirchhoff migration occasionally fall short in identifying distinct targets. Subsequently, we focused on typical subsurface cavities in urban areas, known as Kariz (ancient aqueducts), situated at three locations in Kashan, Iran, encompassing two active (water-carrying) and one dried Kariz. The TR and CTR results demonstrate the applicability of both techniques for additional applications, showcasing their effectiveness in estimating the depth of Kariz galleries using GPR signals.In general, a quantitative analysis of ground-penetrating radar (GPR) data provides insights into the depth of sources and underlying geological features. This study compares the depth information obtained from GPR waves using diverse approaches to detect underground cavities. The processing techniques, including conventional processing (Kirchhoff migration), time reversal (TR) imaging, and the application of continuous wavelet transform (CWT) in TR imaging, known as compensated time reversal (CTR), are evaluated in comparison to commercial software. The predicted depths from TR and CTR align closely with drilling results, while traditional processing and Kirchhoff migration occasionally fall short in identifying distinct targets. Subsequently, we focused on typical subsurface cavities in urban areas, known as Kariz (ancient aqueducts), situated at three locations in Kashan, Iran, encompassing two active (water-carrying) and one dried Kariz. The TR and CTR results demonstrate the applicability of both techniques for additional applications, showcasing their effectiveness in estimating the depth of Kariz galleries using GPR signals.https://www.ijgeophysics.ir/article_194376_fb2759e9b09f8451351f8de4cfa0fa15.pdfانجمن ملی ژئوفیزیک ایرانمجله ژئوفیزیک ایران2008-033618620250120A fast implementation of stochastic 1D elastic seismic full-waveform inversionA fast implementation of stochastic 1D elastic seismic full-waveform inversion9511019259110.30499/ijg.2024.431652.1558FAAliJamasbPh.D. Student, Institute of Geophysics, University of Tehran, IranSeyed-HaniMotavalli-AnbaranAssociate Professor, Institute of Geophysics, University of Tehran, Iran0000-0003-0340-5209Journal Article20231220We present a fast implementation of a 1D elastic full-waveform inversion for reconstructing the elastic structure of the subsurface. The FWI is an inversion algorithm that directly models the full seismic wavefield by solving a semi-analytical form of the elastic wave equation for a 1D layered earth model known as the reflectivity method. The input seismic data are pre-conditioned angle-gathers. The inversion is done using a stochastic algorithm known as PSOES, a fast hybrid stochastic optimization algorithm. Our work primarily contributes to accelerating the computation times required for the inversion, with the goal of developing a strategy that enables code implementation at production scales. Additionally, we are working on creating a framework for conducting joint inversions with potential field data. The computational cost of the FWI is directly proportional to the number of unknowns in the inversion problem, which correlates with the vertical resolution of model (i.e., the layer thicknesses in the 1D Earth model) and the maximum depth of the study. However, the relationship is not linear because increasing the number of unknowns affects the run time of both the forward and inverse problems. On the other hand, the quality of the solution highly depends on the vertical resolution since modeling the higher frequencies in the data requires a relatively small vertical thickness. An optimum implementation of the FWI could result in calculating 1D elastic profiles of the subsurface which could be used for constraining the inversion of potential field data over sedimentary basins.We present a fast implementation of a 1D elastic full-waveform inversion for reconstructing the elastic structure of the subsurface. The FWI is an inversion algorithm that directly models the full seismic wavefield by solving a semi-analytical form of the elastic wave equation for a 1D layered earth model known as the reflectivity method. The input seismic data are pre-conditioned angle-gathers. The inversion is done using a stochastic algorithm known as PSOES, a fast hybrid stochastic optimization algorithm. Our work primarily contributes to accelerating the computation times required for the inversion, with the goal of developing a strategy that enables code implementation at production scales. Additionally, we are working on creating a framework for conducting joint inversions with potential field data. The computational cost of the FWI is directly proportional to the number of unknowns in the inversion problem, which correlates with the vertical resolution of model (i.e., the layer thicknesses in the 1D Earth model) and the maximum depth of the study. However, the relationship is not linear because increasing the number of unknowns affects the run time of both the forward and inverse problems. On the other hand, the quality of the solution highly depends on the vertical resolution since modeling the higher frequencies in the data requires a relatively small vertical thickness. An optimum implementation of the FWI could result in calculating 1D elastic profiles of the subsurface which could be used for constraining the inversion of potential field data over sedimentary basins.https://www.ijgeophysics.ir/article_192591_a18ba1c7d8c9c3668c400a2c91866241.pdfانجمن ملی ژئوفیزیک ایرانمجله ژئوفیزیک ایران2008-033618620250120Insights from the 2017 and 2020 Mw ~5 earthquakes around Tehran: Assessing seismicity and physical and social vulnerabilityInsights from the 2017 and 2020 Mw ~5 earthquakes around Tehran: Assessing seismicity and physical and social vulnerability11112819997410.30499/ijg.2024.445644.1579FAMohammadrezaJamalreyhaniPh.D., Southern University of Science and Technology, Shenzhen, China0000-0003-4181-7175AfsharHatamiPh.D., University of Kharazmi, Tehran, IranMirAliHassanzadehPh.D., Institute for Advanced Studies in Basic Sciences (IASBS), Department of Earth Sciences, Zanjan, Iran0000-0002-7601-077XPınarBüyükakpinarAssociate Professor, GFZ German Research Centre for Geosciences, German, Potsdam0000-0001-8461-674XRaminMovaghariPh.D., Southern University of Science and Technology, Shenzhen, ChinaJournal Article20240225Tehran is one of the most earthquake-prone cities globally. This vast urban center, with a population exceeding 10 million, is intersected by several active faults, presenting significant seismic hazards. The occurrence of two M<sub>w</sub> ~5 earthquakes in December 2017 near Malard and May 2020 near Damavand, further underscores the urgent need for comprehensive studies in the capital of Iran. his analysis primarily focuses on the 2017 and 2020 seismic events and their causative faults. Additionally, we highlight the limitations of Tehran's seismic monitoring and active faults map by addressing examples of unidentified seismic unrest and faults. By tackling the significant challenges of seismic studies and evaluating the preparedness of people and cities for a major earthquake, we draw insights from recent earthquakes around Tehran. Results show that the Malard and Damavand earthquakes occurred on the previously unknown and Mosha faults, respectively. Sparse seismic stations limit route detection thresholds and location accuracy of seismicity near Tehran. In addition, we show that the dispersion of population and distressed fabrics in Tehran is clustered, and the vulnerability to earthquakes is linked to both physical and social factors. This study holds immense importance in enhancing seismological research and risk reduction strategies for the Tehran province.
Tehran is one of the most earthquake-prone cities globally. This vast urban center, with a population exceeding 10 million, is intersected by several active faults, presenting significant seismic hazards. The occurrence of two M<sub>w</sub> ~5 earthquakes in December 2017 near Malard and May 2020 near Damavand, further underscores the urgent need for comprehensive studies in the capital of Iran. his analysis primarily focuses on the 2017 and 2020 seismic events and their causative faults. Additionally, we highlight the limitations of Tehran's seismic monitoring and active faults map by addressing examples of unidentified seismic unrest and faults. By tackling the significant challenges of seismic studies and evaluating the preparedness of people and cities for a major earthquake, we draw insights from recent earthquakes around Tehran. Results show that the Malard and Damavand earthquakes occurred on the previously unknown and Mosha faults, respectively. Sparse seismic stations limit route detection thresholds and location accuracy of seismicity near Tehran. In addition, we show that the dispersion of population and distressed fabrics in Tehran is clustered, and the vulnerability to earthquakes is linked to both physical and social factors. This study holds immense importance in enhancing seismological research and risk reduction strategies for the Tehran province.
https://www.ijgeophysics.ir/article_199974_1ee8f14f1e7154840515a3d8cd5c0252.pdfانجمن ملی ژئوفیزیک ایرانمجله ژئوفیزیک ایران2008-033618620250120Chi angle scan for investigating gas water contact of a Pliocene reservoir in the offshore East Nile Delta, EgyptChi angle scan for investigating gas water contact of a Pliocene reservoir in the offshore East Nile Delta, Egypt12913719812410.30499/ijg.2024.448952.1587FAAiaDahrougAssistant Professor, Geophysics Department, Faculty of Science, Cairo University, Cairo, EgyptMagedFahimM.Sc Graduate, GeoEnergy Petroleum Services, Cairo, EgyptJournal Article20240317One of the main targets within the oil and gas industry is mainly the prediction of both fluids and lithology. Extended Elastic Impedance (EEI) technique is strongly recommended in facilitating reservoir characterization and in distinguishing between seismic amplitude anomalies caused by lithology and those caused by hydrocarbon. Chi angle scan range from 0° to 90° has been conducted to investigate a Pliocene prospect in the offshore East Nile Delta (ND), Egypt. The presence of a remarkable Gas Water Contact (GWC) in the study area helped in investigating the generated EEI volumes. The projections of Chi angles were either affected by lithology only or fluids only, or both lithology and fluids. The fluid volume was estimated at EEI35°, where the top of the gas sand is continuous because of the huge contrast with the overlaying shale and the high amplitude of the gas sand was shut off because of the variation of the fluid type from gas to water. This volume could clearly demonstrate the variation of different fluids with minimum lithology effect. The lithology volume with minimum effect of fluid was estimated at EEI90° (gradient volume), the bottom of the sand was shown on this volume regardless the type of the fluid. However, the base was challenging because of the insignificant contrast between the brine sand and the underlaying shale. The findings of this study can help in better understanding the implication of EEI technique in investigating a Pliocene gas prospect and delineating possible recommended locations for drilling in this field. Moreover, the results show how the technique successfully discriminates between different lithology and fluids.One of the main targets within the oil and gas industry is mainly the prediction of both fluids and lithology. Extended Elastic Impedance (EEI) technique is strongly recommended in facilitating reservoir characterization and in distinguishing between seismic amplitude anomalies caused by lithology and those caused by hydrocarbon. Chi angle scan range from 0° to 90° has been conducted to investigate a Pliocene prospect in the offshore East Nile Delta (ND), Egypt. The presence of a remarkable Gas Water Contact (GWC) in the study area helped in investigating the generated EEI volumes. The projections of Chi angles were either affected by lithology only or fluids only, or both lithology and fluids. The fluid volume was estimated at EEI35°, where the top of the gas sand is continuous because of the huge contrast with the overlaying shale and the high amplitude of the gas sand was shut off because of the variation of the fluid type from gas to water. This volume could clearly demonstrate the variation of different fluids with minimum lithology effect. The lithology volume with minimum effect of fluid was estimated at EEI90° (gradient volume), the bottom of the sand was shown on this volume regardless the type of the fluid. However, the base was challenging because of the insignificant contrast between the brine sand and the underlaying shale. The findings of this study can help in better understanding the implication of EEI technique in investigating a Pliocene gas prospect and delineating possible recommended locations for drilling in this field. Moreover, the results show how the technique successfully discriminates between different lithology and fluids.https://www.ijgeophysics.ir/article_198124_ed77545d550c32a0f017bb9d8dfe3c20.pdf