انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 19 6 2026 01 21 Application of 2D inversion of apparent resistivity and RQD data in identification of granite massif quality Application of 2D inversion of apparent resistivity and RQD data in identification of granite massif quality 1 17 207806 10.30499/ijg.2024.454299.1595 FA Ali Akbar Moradi Master of geophysics, Department of Physics, Faculty of Science, Arak University, Arak, Iran 0000-0001-6582-624X Mahmoud Mirzaei Associate Professor, Department of Physics, Faculty of Science, Arak University, Arak, Iran 0000-0002-8488-4135 Mahdi Abbasi Master of Civil Engineering, Immansazan Institute of Consulting Engineers, Tehran, Iran Journal Article 2024 04 26 Collecting geotechnical information of subsurface formations is very important in creating water transfer structures and digging tunnels. Knowing the quality of rock structures in this regard can be done with the help of using geoelectric techniques. In order to determine the different subsurface geological structures and the quality of the granite rocks, the apparent resistivity data were collected by Vertical Electric Sounding (VES) method with the Schlumberger array in Glass area, located in the northwest of Iran. By performing two-dimensional inversion of the data using the Res2DInv software, tomograms of resistivity values distributed along each profile are constructed. Then, the obtained geoelectric sections are interpreted by means of geological and boreholes information to delineate the different rock structures in the study area. The study area includes all the weathering grades of formations from sandy soil to fresh rock. The results of the tests conducted on the samples taken from the boreholes drilled in the study area serve as a direct check for the results of the resistivity measurements interpretation. Interpretation results can provide an evaluation of the advantages and limitations of the geophysical method used. They also can depict a structural model of subsurface rock masses, showing the relationship between physical properties and geotechnical parameters like Rock Quality Designation (RQD) and the degree of weathering. In the geoelectric sections, resistivity variations in both vertical and horizontal directions are linked to different geological structures and discontinuities. The quality of granite rock masses, in terms of compaction or weathering, is assessed by analyzing resistivity values within the geoelectric sections. These findings on the quality of granite rock masses are compared and validated against borehole sample test results. Collecting geotechnical information of subsurface formations is very important in creating water transfer structures and digging tunnels. Knowing the quality of rock structures in this regard can be done with the help of using geoelectric techniques. In order to determine the different subsurface geological structures and the quality of the granite rocks, the apparent resistivity data were collected by Vertical Electric Sounding (VES) method with the Schlumberger array in Glass area, located in the northwest of Iran. By performing two-dimensional inversion of the data using the Res2DInv software, tomograms of resistivity values distributed along each profile are constructed. Then, the obtained geoelectric sections are interpreted by means of geological and boreholes information to delineate the different rock structures in the study area. The study area includes all the weathering grades of formations from sandy soil to fresh rock. The results of the tests conducted on the samples taken from the boreholes drilled in the study area serve as a direct check for the results of the resistivity measurements interpretation. Interpretation results can provide an evaluation of the advantages and limitations of the geophysical method used. They also can depict a structural model of subsurface rock masses, showing the relationship between physical properties and geotechnical parameters like Rock Quality Designation (RQD) and the degree of weathering. In the geoelectric sections, resistivity variations in both vertical and horizontal directions are linked to different geological structures and discontinuities. The quality of granite rock masses, in terms of compaction or weathering, is assessed by analyzing resistivity values within the geoelectric sections. These findings on the quality of granite rock masses are compared and validated against borehole sample test results.

https://www.ijgeophysics.ir/article_207806_d1eda221762c556f09647551b0ee3242.pdf

انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 19 6 2026 01 21 Weakening of the Arctic polar vortex dynamic barrier in 2006, 2010 and 2014 Weakening of the Arctic polar vortex dynamic barrier in 2006, 2010 and 2014 19 29 208638 10.30499/ijg.2024.478161.1634 FA Vladimir Zuev Professor., Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia 0000-0002-2351-8924 Ekaterina Savelieva Ph.D., Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia 0000-0002-6560-7386 Alexey Pavlinsky Ph.D., Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia Journal Article 2024 09 12 <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi; color: black; mso-themecolor: text1;">The Arctic polar vortex is characterized by significant interannual and intraseasonal variability, causing instability of processes occurring in the winter-spring period in the polar stratosphere of the Northern Hemisphere. The dynamic barrier in the lower stratosphere leads to a decrease in temperature within the polar vortex, which is necessary for the formation of polar stratospheric clouds involved in the chlorine cycle of ozone depletion. In the middle and upper stratosphere, the dynamic barrier prevents air masses from the subpolar region from penetrating into the vortex, isolating the atmosphere inside the vortex from the outside. Using the vortex delineation method, based on the ERA5 reanalysis data, we examined the criteria for the weakening of the dynamic barrier in the middle and upper stratosphere and the features of the vertical dynamics of the Arctic polar vortex in 2006, 2010 and 2014. In 2006 and 2010, sudden stratospheric warmings were observed: on 21 January 2006, as a result of a significant displacement of the vortex, and on 9 February 2010, as a result of the vortex splitting. During the winter of 2014, the polar vortex was strong and persistent, taking on an elliptical shape in January and February. In the studied years, the breakdown of the Arctic polar vortex occurred in January 2006, February 2010 and March 2014, respectively. Despite the different time periods of the polar vortex breakdown, in each case it was observed after the weakening of the dynamic barrier. A weakening of the dynamic barrier (accompanied by a change in temperature inside the vortex) was observed with a local decrease in wind speed along the vortex edge below 27, 28 and 29 m/s at the 10, 7 and 5 hPa levels, respectively. The polar vortex breakdown occurred simultaneously with or shortly after the decrease in mean wind speed along the vortex edge below 41, 43, and 45 m/s at the 10, 7, and 5 hPa levels, respectively. The weakening of the dynamic barrier in the studied years was often not observed along the entire vertical extent of the polar vortex. In all cases, the weakening and subsequent breakdown of the Arctic polar vortex was first observed in the upper stratosphere and then spread into the middle and lower stratosphere. <span dir="RTL" lang="AR-SA" style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi; color: black; mso-themecolor: text1;"> <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi; color: black; mso-themecolor: text1;">The Arctic polar vortex is characterized by significant interannual and intraseasonal variability, causing instability of processes occurring in the winter-spring period in the polar stratosphere of the Northern Hemisphere. The dynamic barrier in the lower stratosphere leads to a decrease in temperature within the polar vortex, which is necessary for the formation of polar stratospheric clouds involved in the chlorine cycle of ozone depletion. In the middle and upper stratosphere, the dynamic barrier prevents air masses from the subpolar region from penetrating into the vortex, isolating the atmosphere inside the vortex from the outside. Using the vortex delineation method, based on the ERA5 reanalysis data, we examined the criteria for the weakening of the dynamic barrier in the middle and upper stratosphere and the features of the vertical dynamics of the Arctic polar vortex in 2006, 2010 and 2014. In 2006 and 2010, sudden stratospheric warmings were observed: on 21 January 2006, as a result of a significant displacement of the vortex, and on 9 February 2010, as a result of the vortex splitting. During the winter of 2014, the polar vortex was strong and persistent, taking on an elliptical shape in January and February. In the studied years, the breakdown of the Arctic polar vortex occurred in January 2006, February 2010 and March 2014, respectively. Despite the different time periods of the polar vortex breakdown, in each case it was observed after the weakening of the dynamic barrier. A weakening of the dynamic barrier (accompanied by a change in temperature inside the vortex) was observed with a local decrease in wind speed along the vortex edge below 27, 28 and 29 m/s at the 10, 7 and 5 hPa levels, respectively. The polar vortex breakdown occurred simultaneously with or shortly after the decrease in mean wind speed along the vortex edge below 41, 43, and 45 m/s at the 10, 7, and 5 hPa levels, respectively. The weakening of the dynamic barrier in the studied years was often not observed along the entire vertical extent of the polar vortex. In all cases, the weakening and subsequent breakdown of the Arctic polar vortex was first observed in the upper stratosphere and then spread into the middle and lower stratosphere. <span dir="RTL" lang="AR-SA" style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi; color: black; mso-themecolor: text1;">

https://www.ijgeophysics.ir/article_208638_308cc985ad58bf6722beec67f5049b4a.pdf

انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 19 6 2026 01 21 Seasonal changes of stability and double diffusive processes in the pit of the Strait of Hormuz Seasonal changes of stability and double diffusive processes in the pit of the Strait of Hormuz 31 43 209888 10.30499/ijg.2024.435204.1565 FA Farzaneh Mohammadpour M.Sc., Department of Nonliving Resources of Atmosphere and Ocean, Faculty of Marine Science and Technology, University of Hormozgan, Bandar Abbas, Iran 0009-0005-2035-6172 Maryam Soyuf Jahromi Assistant Professor, Department of Nonliving Resources of Atmosphere and Ocean, Faculty of Marine Science and Technology, University of Hormozgan, Bandar Abbas, Iran 0000-0002-7877-6277 Samad Hamzei Assistant Professor, Iranian National Institute for Oceanography and Atmospheric Science, Tehran, Iran Journal Article 2024 01 11 <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';">Oceanic pits are often<span dir="RTL" style="font-size: 11.0pt; font-family: 'B Zar'; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi;"> <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';">unknown due to their enclosed nature and lack of exchange with the surrounding environment, and they are often overlooked and neglected by researchers. The study area of the current research is a pit located in the Strait of Hormuz, near the south of Greater Tunb Island, which has not been previously studied. Its depth is more than 185 meters, with longitude coordinates of 55.321 degrees East and latitude of 26.122 degrees North. However, the depth of these coordinates has been recorded as 68 meters on GEBCO's international website. <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';">The seasonal data used are temperature and salinity obtained from one seasonal field measurement of the Persian Gulf Explorer in 2018 which were measured using a <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-fareast-language: EN-GB;">CTD (Conductivity, Temperature, and Depth) instrument with a time step of one second. <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';">Then the related graphs of temperature, salinity and potential density were plotted and analyzed in Ocean Data View (ODV) software package. Moreover, the Brunt-Väisälä buoyancy frequency and Turner’s angle were calculated and plotted using ODV. <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-fareast-language: EN-GB;">The average values of each component were calculated by the weighted averaging method in ODV. <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';">The results showed that the pit is generally stable. The surface layer of winter had a higher density than the other seasons, but the summer unexpectedly had a higher density than the other seasons in the deep trapped water of the pit. The results also showed that all three states of stability, instability and double diffusion convection occur in all seasons in the pit. The layers which mostly consist of double diffusion convection were observed in the following order: summer, winter, spring and autumn, respectively. The salt finger regime in warm seasons (spring and summer) and the diffusive convection regime in cold seasons (autumn and winter) had a greater contribution to creating double diffusion convection. The strong diffusive regime in warm and cold season seasons was9% and 4%, respectively, and the weak diffusive regime in warm and cold season seasons was 5% and 22%, respectively. Meanwhile, the strong salt finger regime in warm and cold seasons was 18% and 8%, respectively and the weak salt finger regime in warm and cold seasons was 21% and 9%, respectively. <span style="font-size: 11.0pt; mso-bidi-font-size: 9.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';">The relationship between temperature and stability clearly showed that there was no seasonal thermocline layer in autumn and winter. In summer, the thermocline layer is stable and the surface mixed layer was highly unstable. Surprisingly, both the most stable and unstable layers were located in deep waters of spring.<span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';"> In general, autumn was the most stable season and spring was the most unstable season according to the measured data of the Persian Gulf Explorer (2018) in the pit of Strait of Hormuz, near the south of Greater Tunb. <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';">Oceanic pits are often<span dir="RTL" style="font-size: 11.0pt; font-family: 'B Zar'; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi;"> <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';">unknown due to their enclosed nature and lack of exchange with the surrounding environment, and they are often overlooked and neglected by researchers. The study area of the current research is a pit located in the Strait of Hormuz, near the south of Greater Tunb Island, which has not been previously studied. Its depth is more than 185 meters, with longitude coordinates of 55.321 degrees East and latitude of 26.122 degrees North. However, the depth of these coordinates has been recorded as 68 meters on GEBCO's international website. <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';">The seasonal data used are temperature and salinity obtained from one seasonal field measurement of the Persian Gulf Explorer in 2018 which were measured using a <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-fareast-language: EN-GB;">CTD (Conductivity, Temperature, and Depth) instrument with a time step of one second. <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';">Then the related graphs of temperature, salinity and potential density were plotted and analyzed in Ocean Data View (ODV) software package. Moreover, the Brunt-Väisälä buoyancy frequency and Turner’s angle were calculated and plotted using ODV. <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-fareast-language: EN-GB;">The average values of each component were calculated by the weighted averaging method in ODV. <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';">The results showed that the pit is generally stable. The surface layer of winter had a higher density than the other seasons, but the summer unexpectedly had a higher density than the other seasons in the deep trapped water of the pit. The results also showed that all three states of stability, instability and double diffusion convection occur in all seasons in the pit. The layers which mostly consist of double diffusion convection were observed in the following order: summer, winter, spring and autumn, respectively. The salt finger regime in warm seasons (spring and summer) and the diffusive convection regime in cold seasons (autumn and winter) had a greater contribution to creating double diffusion convection. The strong diffusive regime in warm and cold season seasons was9% and 4%, respectively, and the weak diffusive regime in warm and cold season seasons was 5% and 22%, respectively. Meanwhile, the strong salt finger regime in warm and cold seasons was 18% and 8%, respectively and the weak salt finger regime in warm and cold seasons was 21% and 9%, respectively. <span style="font-size: 11.0pt; mso-bidi-font-size: 9.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';">The relationship between temperature and stability clearly showed that there was no seasonal thermocline layer in autumn and winter. In summer, the thermocline layer is stable and the surface mixed layer was highly unstable. Surprisingly, both the most stable and unstable layers were located in deep waters of spring.<span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'B Zar';"> In general, autumn was the most stable season and spring was the most unstable season according to the measured data of the Persian Gulf Explorer (2018) in the pit of Strait of Hormuz, near the south of Greater Tunb.

https://www.ijgeophysics.ir/article_209888_ff84eeace059e44588c3bd6c6ef0f399.pdf

انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 19 6 2026 01 21 Evaluation of daily satellite rainfall product during high dense rainstorm for flood prediction over Iraq Evaluation of daily satellite rainfall product during high dense rainstorm for flood prediction over Iraq 45 58 210067 10.30499/ijg.2024.475075.1625 FA Zaidoon Abdulrazzaq Ph.D., Space Research and Technology Center, Scientific Research Commission, Baghdad, Iraq 0000-0002-0234-0872 Journal Article 2024 08 26 Precipitation in regions characterized by intricate terrain is frequently identified by significant variability and inadequate observation, which hampers efforts to effectively address water resource management concerns. In this study, we assess the accuracy of remote sensing and ground station-based gridded precipitation products in Iraq by comparing them to weather station precipitation observations on a daily basis. Moreover, the possibility of rainfall satellite-derived data to predict potential floods and damages in selected areas in eastern and central Iraq during previous rainstorms was studied. In the present study, the accuracy of GPM satellite precipitation data during a highly dense rainstorm for flood prediction over Iraq was evaluated. The findings revealed a strong agreement between satellite precipitation data and rain-gauge data, with a correlation coefficient of 0.88, indicating a high level of accuracy. Hence, it is ideal for utilization in meteorological and hydrological investigations as well as for the creation of rainfall contour maps. Based on the overly model that has been produced for the areas threatened by flooding then, the extraction function was used to polygons of these areas. Statistical calculations showed the areas vulnerable to flooding in the event of continued recurring rainstorms, as the total area reached 4,461,241 km2. Precipitation in regions characterized by intricate terrain is frequently identified by significant variability and inadequate observation, which hampers efforts to effectively address water resource management concerns. In this study, we assess the accuracy of remote sensing and ground station-based gridded precipitation products in Iraq by comparing them to weather station precipitation observations on a daily basis. Moreover, the possibility of rainfall satellite-derived data to predict potential floods and damages in selected areas in eastern and central Iraq during previous rainstorms was studied. In the present study, the accuracy of GPM satellite precipitation data during a highly dense rainstorm for flood prediction over Iraq was evaluated. The findings revealed a strong agreement between satellite precipitation data and rain-gauge data, with a correlation coefficient of 0.88, indicating a high level of accuracy. Hence, it is ideal for utilization in meteorological and hydrological investigations as well as for the creation of rainfall contour maps. Based on the overly model that has been produced for the areas threatened by flooding then, the extraction function was used to polygons of these areas. Statistical calculations showed the areas vulnerable to flooding in the event of continued recurring rainstorms, as the total area reached 4,461,241 km2.

https://www.ijgeophysics.ir/article_210067_4ead29d5ccaf3697a3ec50e0e2a22d98.pdf

انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 19 6 2026 01 21 Solar dynamics and cosmic ray intensity: statistical analysis from 1986 to 2019 Solar dynamics and cosmic ray intensity: statistical analysis from 1986 to 2019 59 70 211275 10.30499/ijg.2024.476329.1627 FA Nisha R Ph.D. Student, Research Scholar, Department of Physics, Women’s Christian College, Nagercoil, India 0000-0003-4173-3318 Shanthi G Associate Professor, Department of Physics and Research Centre, Women’s Christian College, Nagercoil, India Journal Article 2024 08 31 <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi; color: black; mso-themecolor: text1;">Interpretations of cosmic ray intensity reflect various solar activities, particularly influenced by changes in solar wind plasma within the heliosphere. To investigate the periodic behavior and relationship of cosmic ray intensity with sunspot number, solar wind plasma velocity, solar wind temperature, and interplanetary magnetic field (IMF), we employed daily and annual data analysis of solar activity from September 1986 to December 2019. In analyzing the relationship between cosmic ray intensity (CRI) and solar activity, the statistical method of "cross-correlation", although widely employed in various disciplines and applications, has been a staple for investigating such relationships. The primary goal of the cross-correlation method is to study the relationship between CRI and solar activity parameters and apply this information in statistical analyses across various solar cycles or periods. In this study, calculations for the most recent solar activity cycles are provided. The analysis confirms a negative correlation between the intensity of cosmic rays and the number of sunspots, with solar wind parameters exhibiting an anachronistic phase relationship also showing a negative correlation. Furthermore, the anti-correlation of cosmic ray intensity with solar wind parameters is expected to yield insights into space weather near Earth. <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi; color: black; mso-themecolor: text1;">Interpretations of cosmic ray intensity reflect various solar activities, particularly influenced by changes in solar wind plasma within the heliosphere. To investigate the periodic behavior and relationship of cosmic ray intensity with sunspot number, solar wind plasma velocity, solar wind temperature, and interplanetary magnetic field (IMF), we employed daily and annual data analysis of solar activity from September 1986 to December 2019. In analyzing the relationship between cosmic ray intensity (CRI) and solar activity, the statistical method of "cross-correlation", although widely employed in various disciplines and applications, has been a staple for investigating such relationships. The primary goal of the cross-correlation method is to study the relationship between CRI and solar activity parameters and apply this information in statistical analyses across various solar cycles or periods. In this study, calculations for the most recent solar activity cycles are provided. The analysis confirms a negative correlation between the intensity of cosmic rays and the number of sunspots, with solar wind parameters exhibiting an anachronistic phase relationship also showing a negative correlation. Furthermore, the anti-correlation of cosmic ray intensity with solar wind parameters is expected to yield insights into space weather near Earth.

https://www.ijgeophysics.ir/article_211275_3602e5f48e3ede784842c65220f25881.pdf

انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 19 6 2026 01 21 Nonlinear travel-time cross-hole tomography with overlapping group sparse total variation regularization Nonlinear travel-time cross-hole tomography with overlapping group sparse total variation regularization 71 83 212309 10.30499/ijg.2024.457446.1602 FA Yaser Soufi Ph.D. Student, Islamic Azad University, Science and Research Branch, Tehran Iran Mohammad Ali Riahi Professor, Institute of Geophysics, University of Tehran, Iran 0000-0002-3827-4467 Reza Heidari Assistant Professor, Islamic Azad University, Science and Research Branch, Tehran Iran 0000-0002-3827-4467 Mahmood Mehramooz Assistant Professor, Islamic Azad University, Science and Research Branch, Tehran Iran Journal Article 2024 05 14 <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi;">To address the inherent ill-posedness of the geophysical inverse problems, it is necessary to include a suitable regularization function in the corresponding optimization framework. Typically, the choice of the regularization function depends on prior assumptions about the geometric characteristics of the unknown model parameters, e.g., smoothness or blockiness. First-order total variation regularization (TV) allows the reconstruction of well-defined edges and models exhibiting block-like characteristics. However, it is associated with the generation of undesirable staircase artifacts. This study applies a novel approach for removing staircase artifacts using a combined second-order non-convex total variation with overlapping group sparse regularizer. This regularizer aims to smooth out the staircase effect while still keeping the edges of the model. Moreover, the study applies the proposed method for the nonlinear seismic cross-hole tomography problems, where the goal is to reconstruct both smooth and blocky features of the model and avoid staircase artifacts of the TV regularization. The numerical examples indicate the efficiency of the proposed regularization method. <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi;">To address the inherent ill-posedness of the geophysical inverse problems, it is necessary to include a suitable regularization function in the corresponding optimization framework. Typically, the choice of the regularization function depends on prior assumptions about the geometric characteristics of the unknown model parameters, e.g., smoothness or blockiness. First-order total variation regularization (TV) allows the reconstruction of well-defined edges and models exhibiting block-like characteristics. However, it is associated with the generation of undesirable staircase artifacts. This study applies a novel approach for removing staircase artifacts using a combined second-order non-convex total variation with overlapping group sparse regularizer. This regularizer aims to smooth out the staircase effect while still keeping the edges of the model. Moreover, the study applies the proposed method for the nonlinear seismic cross-hole tomography problems, where the goal is to reconstruct both smooth and blocky features of the model and avoid staircase artifacts of the TV regularization. The numerical examples indicate the efficiency of the proposed regularization method.

https://www.ijgeophysics.ir/article_212309_1dc328a90c3d09ba571577935410481d.pdf

انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 19 6 2026 01 21 Spatial reconstruction of geological features distribution based on remote sensing model using convolutional neural network algorithm in Patuha geothermal field, Indonesia Spatial reconstruction of geological features distribution based on remote sensing model using convolutional neural network algorithm in Patuha geothermal field, Indonesia 85 104 212701 10.30499/ijg.2025.476758.1629 FA Widya Utama Associate Professor, Department of Geophysics Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia 0000-0002-7883-6508 Ira Mutiara Anjasmara Associate Professor, Department of Geophysics Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia 0000-0001-5674-7849 Dhea Pratama Novian Putra M.Sc., Department of Geomatics Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia 0000-0003-3436-9554 Daniel Sahat Rezeki Hutagalung Bachelor, Department of Geomatics Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia 0009-0004-0521-2931 Muhammad Himam Awali Bachelor, Department of Geomatics Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia 0000-0002-6499-7423 Sherly Ardhya Garini Ph.D. Student, Department of Informatics, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia 0000-0002-8238-7098 Rista Fitri Indriani M.Sc., Department of Geomatics Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia 0000-0003-0539-155X Journal Article 2024 09 04 Recent advancements in remote sensing technology have optimized spatial data by enhancing the resolution of field measurement data. Regional geological maps are still used to validate geoscience models because of their high reliability, which is based on field measurements, but they have relatively low spatial resolution. Combining remote sensing models with machine learning algorithms offers a promising method to reconstruct regional geological maps into high-resolution geological maps, especially in volcanic regions with active geothermal systems such as the Patuha Geothermal Field in Indonesia. Models derived from pre-processed satellite gravity data and normalized satellite images, with standardized pixel raster sizes, form the quantitative basis for reconstructing regional geological map models. The Convolutional Neural Network (CNN) algorithm serves as the computational basis for reconstructing spatial models. The results of spatial reconstruction modeling using remote sensing data provide detailed insights into the distribution of geological features, achieving an accuracy rate of 81.26%. These varying geological feature zones are likely related to the dynamics of active volcanic regions. Since the active volcanic activity, geological fault structures have been formed and could be identified by combination of derivative analysis and remote sensing approach. Second Vertical Derivative (SVD) provides physical characteristics of active fault planes, integrating it with remote sensing analysis to indicate fault planes appeared in the surface. There is a clear correlation between the distribution of reconstructed lithological features and geological fault planes. Areas with a high concentration of fault planes often have a more diverse distribution of geological features, likely due to the influence of active faults, volcanic activity, and material erosion. Adding hyperparameters and geological feature constraints to the machine learning algorithm is a promising option for further research in this area of geological map reconstruction. Recent advancements in remote sensing technology have optimized spatial data by enhancing the resolution of field measurement data. Regional geological maps are still used to validate geoscience models because of their high reliability, which is based on field measurements, but they have relatively low spatial resolution. Combining remote sensing models with machine learning algorithms offers a promising method to reconstruct regional geological maps into high-resolution geological maps, especially in volcanic regions with active geothermal systems such as the Patuha Geothermal Field in Indonesia. Models derived from pre-processed satellite gravity data and normalized satellite images, with standardized pixel raster sizes, form the quantitative basis for reconstructing regional geological map models. The Convolutional Neural Network (CNN) algorithm serves as the computational basis for reconstructing spatial models. The results of spatial reconstruction modeling using remote sensing data provide detailed insights into the distribution of geological features, achieving an accuracy rate of 81.26%. These varying geological feature zones are likely related to the dynamics of active volcanic regions. Since the active volcanic activity, geological fault structures have been formed and could be identified by combination of derivative analysis and remote sensing approach. Second Vertical Derivative (SVD) provides physical characteristics of active fault planes, integrating it with remote sensing analysis to indicate fault planes appeared in the surface. There is a clear correlation between the distribution of reconstructed lithological features and geological fault planes. Areas with a high concentration of fault planes often have a more diverse distribution of geological features, likely due to the influence of active faults, volcanic activity, and material erosion. Adding hyperparameters and geological feature constraints to the machine learning algorithm is a promising option for further research in this area of geological map reconstruction.

https://www.ijgeophysics.ir/article_212701_498887d3a72d7f37c5548d963c55f4f3.pdf

انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 19 6 2026 01 21 Effects of meteorological factors and air pollution on the spread and transmission patterns of COVID-19 in Iran Effects of meteorological factors and air pollution on the spread and transmission patterns of COVID-19 in Iran 105 123 213604 10.30499/ijg.2025.486036.1647 FA Farahnaz Fazel Rastgar Ph.D., Discipline of Physics, School of Chemistry and Physics, University of KwaZulu-Natal, South Africa 0000-0002-3904-4313 Sakineh Khansalari Assistant Professor, Research Institute of Meteorology and Atmospheric Science, Tehran, Iran 0000-0001-9039-2818 Venkataraman Sivakumar Professor, S. V. Raman Researchers Roadmap, Westville, South Africa Journal Article 2024 10 29 This study investigates the understanding meteorological and environmental drivers of COVID-19 transmission in Iran. This work examines multiple datasets and models obtained from NASA's Modern-Era Retrospective Analysis for Research and Applications (MERRA) database and ERA5 hourly data from the European Centre for Medium-Range Weather Forecasts (ECMWF). The study underscores the critical role of meteorological factors in the transmission dynamics of COVID-19, emphasizing the interplay of wind patterns, atmospheric levels, and humidity. Wind speeds at 10 meters and 850 hPa show strong positive correlations with transmission risk (correlation coefficients: 0.76 and 0.75). This suggests that stronger surface winds may facilitate the airborne spread of viral particles. Conversely, reduced wind speeds at 700 and 500 hPa show significant negative correlations (-0.53 and -0.70), highlighting how atmospheric stratification affects virus dispersion. Also, this work shows a negative correlation exists between relative humidity and COVID-19 transmission. Higher humidity may suppress the virus's airborne viability or dispersal, emphasizing the need for effective ventilation, especially in low-humidity indoor environments. The study also observed a notable increase in air pollutants—specifically, NO2, Pm2.5, SO2, and low-level ozone—during the fifth COVID-19 wave. This is in comparison with short pre- and post-events of the peak wave, despite lockdown measures. This caused the pollution accumulation without ventilation due to the specific stable weather. This rise in pollutants highlights the intersection of public health challenges posed by both viruses spread and air quality. The study also noted an expected increase in ozone levels during the summer months of the fifth wave, attributed to high temperatures that generally foster ozone formation. However, the analysis suggests that temperature alone does not significantly influence COVID-19 transmission risk, highlighting the complex role of multiple variables in influencing the spread of virus. Additionally, in the stable atmospheric conditions of the middle and upper levels during hot summer months, both ozone and particulate matter pollution correlated positively with transmission risk. This relationship was especially evident under unusually high temperatures (0.57K above normal) and hazy conditions characterized by increased aerosol optical depth (AOD) in August 2021. This study investigates the understanding meteorological and environmental drivers of COVID-19 transmission in Iran. This work examines multiple datasets and models obtained from NASA's Modern-Era Retrospective Analysis for Research and Applications (MERRA) database and ERA5 hourly data from the European Centre for Medium-Range Weather Forecasts (ECMWF). The study underscores the critical role of meteorological factors in the transmission dynamics of COVID-19, emphasizing the interplay of wind patterns, atmospheric levels, and humidity. Wind speeds at 10 meters and 850 hPa show strong positive correlations with transmission risk (correlation coefficients: 0.76 and 0.75). This suggests that stronger surface winds may facilitate the airborne spread of viral particles. Conversely, reduced wind speeds at 700 and 500 hPa show significant negative correlations (-0.53 and -0.70), highlighting how atmospheric stratification affects virus dispersion. Also, this work shows a negative correlation exists between relative humidity and COVID-19 transmission. Higher humidity may suppress the virus's airborne viability or dispersal, emphasizing the need for effective ventilation, especially in low-humidity indoor environments. The study also observed a notable increase in air pollutants—specifically, NO2, Pm2.5, SO2, and low-level ozone—during the fifth COVID-19 wave. This is in comparison with short pre- and post-events of the peak wave, despite lockdown measures. This caused the pollution accumulation without ventilation due to the specific stable weather. This rise in pollutants highlights the intersection of public health challenges posed by both viruses spread and air quality. The study also noted an expected increase in ozone levels during the summer months of the fifth wave, attributed to high temperatures that generally foster ozone formation. However, the analysis suggests that temperature alone does not significantly influence COVID-19 transmission risk, highlighting the complex role of multiple variables in influencing the spread of virus. Additionally, in the stable atmospheric conditions of the middle and upper levels during hot summer months, both ozone and particulate matter pollution correlated positively with transmission risk. This relationship was especially evident under unusually high temperatures (0.57K above normal) and hazy conditions characterized by increased aerosol optical depth (AOD) in August 2021.

https://www.ijgeophysics.ir/article_213604_16bde39214bca1d8d8dc4e6d5b10b553.pdf

انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 19 6 2026 01 21 Determining apparent source time function (ASTF) of seismic events through empirical green function analysis (a case study of Khoy 2023 earthquake) Determining apparent source time function (ASTF) of seismic events through empirical green function analysis (a case study of Khoy 2023 earthquake) 125 138 214923 10.30499/ijg.2025.480141.1638 FA Khalil Bakhtiari Asl M.Sc., Department of Geomatics Engineering, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran 0009-0001-9539-5484 Vladimir Plicka Ph.D., Department of Geophysics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic 0000-0002-3316-8825 Khosro Moghtased- Azar Associate Professor, Department of Geomatics Engineering, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran Journal Article 2024 09 26 <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi;">The study examines the Apparent Source Time Function (ASTF) for four seismic stations (MRD, SDS1, URUN, and MAHB) in relation to the Khoy earthquake. By employing the method developed by <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi;">(Plicka, et al. 2022)<span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi;">, we meticulously calculate the ASTFs to investigate the temporal distribution of seismic energy release during the earthquake. Our analysis reveals significant variations in ASTF duration across the different stations. Specifically, the MRD station exhibits a notably short ASTF duration of 5 seconds, whereas the URUN station shows a considerably longer ASTF duration of 18 seconds. The SDS1 and MAHB stations fall in between, with ASTF durations of 15 seconds and 12 seconds, respectively. These observed variations in ASTF durations likely indicate differences in fault properties and rupture dynamics at each station. The shorter ASTF at MRD may suggest a more abrupt energy release, while the longer ASTF at SDS1 could imply a more prolonged rupture process. The intermediate durations at URUN and MAHB further highlight the complexity and variability of seismic energy release mechanisms. Our findings contribute valuable insights into seismic hazard assessment and fault characterization in the Khoy region. By applying the ASTF calculation method to this specific case study, we demonstrate its utility in enhancing our understanding of earthquake dynamics. This innovative application underscores the importance of ASTF analysis in seismic studies and its potential to inform more accurate seismic hazard models. Furthermore, our research opens up new avenues for future investigations. We suggest that subsequent studies should focus on a broader range of seismic events and stations to validate and refine the ASTF method. Additionally, exploring the relationship between ASTF characteristics and other seismic parameters, such as fault slip and rupture velocity, could provide deeper insights into the underlying mechanisms of earthquake generation. In conclusion, this study not only advances our knowledge of the Khoy earthquake but also highlights the broader applicability of ASTF analysis in seismology. Our work underscores the need for continued research in this area to improve seismic hazard assessments and enhance our understanding of earthquake processes. By integrating ASTF analysis with other geophysical methods, we can develop a more comprehensive picture of seismic activity, ultimately contributing to better preparedness and mitigation strategies in earthquake-prone regions. This holistic approach will be crucial for advancing the field of seismology and ensuring the safety and resilience of communities affected by seismic events. The insights gained from this study can also be applied to other regions with similar seismic profiles, thereby broadening the impact and relevance of our findings. <span dir="RTL" lang="AR-SA" style="font-size: 9.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi;"> <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi;">The study examines the Apparent Source Time Function (ASTF) for four seismic stations (MRD, SDS1, URUN, and MAHB) in relation to the Khoy earthquake. By employing the method developed by <span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi;">(Plicka, et al. 2022)<span style="font-size: 11.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi;">, we meticulously calculate the ASTFs to investigate the temporal distribution of seismic energy release during the earthquake. Our analysis reveals significant variations in ASTF duration across the different stations. Specifically, the MRD station exhibits a notably short ASTF duration of 5 seconds, whereas the URUN station shows a considerably longer ASTF duration of 18 seconds. The SDS1 and MAHB stations fall in between, with ASTF durations of 15 seconds and 12 seconds, respectively. These observed variations in ASTF durations likely indicate differences in fault properties and rupture dynamics at each station. The shorter ASTF at MRD may suggest a more abrupt energy release, while the longer ASTF at SDS1 could imply a more prolonged rupture process. The intermediate durations at URUN and MAHB further highlight the complexity and variability of seismic energy release mechanisms. Our findings contribute valuable insights into seismic hazard assessment and fault characterization in the Khoy region. By applying the ASTF calculation method to this specific case study, we demonstrate its utility in enhancing our understanding of earthquake dynamics. This innovative application underscores the importance of ASTF analysis in seismic studies and its potential to inform more accurate seismic hazard models. Furthermore, our research opens up new avenues for future investigations. We suggest that subsequent studies should focus on a broader range of seismic events and stations to validate and refine the ASTF method. Additionally, exploring the relationship between ASTF characteristics and other seismic parameters, such as fault slip and rupture velocity, could provide deeper insights into the underlying mechanisms of earthquake generation. In conclusion, this study not only advances our knowledge of the Khoy earthquake but also highlights the broader applicability of ASTF analysis in seismology. Our work underscores the need for continued research in this area to improve seismic hazard assessments and enhance our understanding of earthquake processes. By integrating ASTF analysis with other geophysical methods, we can develop a more comprehensive picture of seismic activity, ultimately contributing to better preparedness and mitigation strategies in earthquake-prone regions. This holistic approach will be crucial for advancing the field of seismology and ensuring the safety and resilience of communities affected by seismic events. The insights gained from this study can also be applied to other regions with similar seismic profiles, thereby broadening the impact and relevance of our findings. <span dir="RTL" lang="AR-SA" style="font-size: 9.0pt; mso-ascii-font-family: 'Times New Roman'; mso-ascii-theme-font: major-bidi; mso-hansi-font-family: 'Times New Roman'; mso-hansi-theme-font: major-bidi; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: major-bidi;">

https://www.ijgeophysics.ir/article_214923_2d226a98043c7cb96b76d7385fcf94d6.pdf

انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 19 6 2026 01 21 Local earthquake tomography and 4-D imaging of the Rudbar Lorestan dam in Iran Local earthquake tomography and 4-D imaging of the Rudbar Lorestan dam in Iran 139 150 215536 10.30499/ijg.2025.474489.1626 FA Nasrin Pour Shabani M.Sc., Institute of Geophysics, Department of seismology, University of Tehran, Tehran, Iran Zaher Hossein Shomali Professor, Institute of Geophysics, Department of seismology, University of Tehran, Tehran, Iran 0000-0001-6254-7560 Ahmad Sadidkhouy Associate Professor, Institute of Geophysics, Department of seismology, University of Tehran, Tehran, Iran 0000-0002-7071-045X Journal Article 2024 08 27 This study focuses on analyzing the crustal velocity structure at the Rudbar Dam located in Lorestan Province, using advanced earthquake tomography techniques. Local earthquake tomography is a powerful tool that provides crucial insights into various subsurface structures by generating a three-dimensional (3-D) velocity model of the region. Understanding crustal velocity structures and the anomalies that can arise within them is vital for improving our comprehension of fault geometries and other subsurface features, such as sediment layers, which are essential for regional seismic studies. By detecting these structural anomalies, we can significantly enhance our understanding of the area's tectonic behavior, contributing to better-informed assessments of seismic risks. The research included data from 920 initial earthquakes, which were meticulously recorded by a network of seven short-period seismic stations strategically positioned around the dam. To calculate the crustal structure in this area, we utilized the SimulPS12 software, a robust tool designed for processing and analyzing seismic data to produce accurate velocity models. Initially, we developed and presented a one-dimensional (1-D) velocity model, which serves as a foundational step in the analysis. Following this, we employed the Joint Hypocenter Determination (JHD) method to relocate the earthquakes more precisely, ensuring the accuracy of the subsequent three-dimensional (3-D) velocity model. The resulting 3-D velocity model images clearly depict the region's geological features, particularly highlighting the anticlines characterized by high-velocity cores and the synclines with low-velocity cores. These findings align well with the existing geological evidence, further validating the accuracy and reliability of our model. The study also incorporates a four-dimensional (4-D) tomography approach to analyze temporal changes in the velocity structure. In this context, two distinct time windows were considered for data analysis: one prior to dewater and another after the injection process. This temporal analysis allowed us to observe significant changes in seismic activity, with the seismicity cluster shifting either towards the northwest or southeast following dewater. This movement suggests a correlation between the injection process and the observed seismicity patterns, offering insights into how human activities can influence seismic behavior. By employing 4-D tomography, we concluded that fluctuations in pore pressure, induced by dewater, can have a substantial impact on the mechanical resistance of fault sections. This, in turn, influences seismic activity along the active faults in the region. These findings underscore the importance of monitoring subsurface pressure changes, as they can have direct implications for seismic hazard assessments, especially in regions with active fault systems like Lorestan. This study focuses on analyzing the crustal velocity structure at the Rudbar Dam located in Lorestan Province, using advanced earthquake tomography techniques. Local earthquake tomography is a powerful tool that provides crucial insights into various subsurface structures by generating a three-dimensional (3-D) velocity model of the region. Understanding crustal velocity structures and the anomalies that can arise within them is vital for improving our comprehension of fault geometries and other subsurface features, such as sediment layers, which are essential for regional seismic studies. By detecting these structural anomalies, we can significantly enhance our understanding of the area's tectonic behavior, contributing to better-informed assessments of seismic risks. The research included data from 920 initial earthquakes, which were meticulously recorded by a network of seven short-period seismic stations strategically positioned around the dam. To calculate the crustal structure in this area, we utilized the SimulPS12 software, a robust tool designed for processing and analyzing seismic data to produce accurate velocity models. Initially, we developed and presented a one-dimensional (1-D) velocity model, which serves as a foundational step in the analysis. Following this, we employed the Joint Hypocenter Determination (JHD) method to relocate the earthquakes more precisely, ensuring the accuracy of the subsequent three-dimensional (3-D) velocity model. The resulting 3-D velocity model images clearly depict the region's geological features, particularly highlighting the anticlines characterized by high-velocity cores and the synclines with low-velocity cores. These findings align well with the existing geological evidence, further validating the accuracy and reliability of our model. The study also incorporates a four-dimensional (4-D) tomography approach to analyze temporal changes in the velocity structure. In this context, two distinct time windows were considered for data analysis: one prior to dewater and another after the injection process. This temporal analysis allowed us to observe significant changes in seismic activity, with the seismicity cluster shifting either towards the northwest or southeast following dewater. This movement suggests a correlation between the injection process and the observed seismicity patterns, offering insights into how human activities can influence seismic behavior. By employing 4-D tomography, we concluded that fluctuations in pore pressure, induced by dewater, can have a substantial impact on the mechanical resistance of fault sections. This, in turn, influences seismic activity along the active faults in the region. These findings underscore the importance of monitoring subsurface pressure changes, as they can have direct implications for seismic hazard assessments, especially in regions with active fault systems like Lorestan.

https://www.ijgeophysics.ir/article_215536_39eff323bee3b6ca2417f12420fd07ac.pdf