Saguedo Sawadogo, D. A. Gnabahou, Sibri Alphonse Sandwidi, F. Ouattara
In this paper, we presented the effect of moderate geomagnetic storms on the TEC variation at the Koudougou station (Geo Lat 12° 15 ′ N; Geo Long: -2° 20 ′ E) in Burkina Faso (Africa) during the descending phase of solar cycle 24. For this purpose, four moderate geomagnetic storms without storm sudden commencement (SSC) or sudden impulse (SI) that occurred on May 13, 2015 (Dst: -76 nT), June 08, 2015 (Dst: -73 nT), September 11, 2015 (Dst: -80 nT), and May 08-09, 2016 (Dst: -88nT), were considered. These moderate storms were found to be associated with transients induced by fast solar winds. At the Koudougou station, TEC variation shows a positive response to the different moderate geomagnetic storms studied, with increases of order of 2-21 TECU around 1300-1500 UT except for September 11, 2015, TEC variation which shows sometimes negative responses at a few hours (mainly at night). TEC increases observed are a function of geomagnetic parameter (magnitude and polarity) variation. Storm-induced electric field and neutral winds are the main drivers of TEC changes observed during the selected geomagnetic storms. In addition, it was found that the TEC peak on storm day behaves differently compared to the days before and after the storm depending on whether Dst is positive or negative before southward inversion. Indeed, a TEC small peak relative to the days before and after the storm is observed when Dst is negative before southward inversion, and a larger peak occurs in the opposite case. The reasons for these differences are not investigated in this paper.
{"title":"Koudougou (Burkina Faso, Africa), GPS-TEC Response to Recurrent Geomagnetic Storms during Solar Cycle 24 Declining Phase","authors":"Saguedo Sawadogo, D. A. Gnabahou, Sibri Alphonse Sandwidi, F. Ouattara","doi":"10.1155/2023/4181389","DOIUrl":"https://doi.org/10.1155/2023/4181389","url":null,"abstract":"In this paper, we presented the effect of moderate geomagnetic storms on the TEC variation at the Koudougou station (Geo Lat 12° 15\u0000 \u0000 ′\u0000 \u0000 N; Geo Long: -2° 20\u0000 \u0000 ′\u0000 \u0000 E) in Burkina Faso (Africa) during the descending phase of solar cycle 24. For this purpose, four moderate geomagnetic storms without storm sudden commencement (SSC) or sudden impulse (SI) that occurred on May 13, 2015 (Dst: -76 nT), June 08, 2015 (Dst: -73 nT), September 11, 2015 (Dst: -80 nT), and May 08-09, 2016 (Dst: -88nT), were considered. These moderate storms were found to be associated with transients induced by fast solar winds. At the Koudougou station, TEC variation shows a positive response to the different moderate geomagnetic storms studied, with increases of order of 2-21 TECU around 1300-1500 UT except for September 11, 2015, TEC variation which shows sometimes negative responses at a few hours (mainly at night). TEC increases observed are a function of geomagnetic parameter (magnitude and polarity) variation. Storm-induced electric field and neutral winds are the main drivers of TEC changes observed during the selected geomagnetic storms. In addition, it was found that the TEC peak on storm day behaves differently compared to the days before and after the storm depending on whether Dst is positive or negative before southward inversion. Indeed, a TEC small peak relative to the days before and after the storm is observed when Dst is negative before southward inversion, and a larger peak occurs in the opposite case. The reasons for these differences are not investigated in this paper.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2023-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41410463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Arisbaya, Edy Wijanarko, Warsa, P. Sumintadireja, Y. Sudrajat, L. Handayani, M. Mukti, H. Grandis
In recent years, dozen low-intensity earthquakes occurred in southern Garut, West Java Indonesia; two of them were reported destructive. However, those shallow earthquake clusters are hardly associated with well-known active faults in the area. Hence, we conducted 3D gravity combined with 2D magnetotellurics (MT) inversions to study the subsurface. Gravity and MT modeling confirm a basin with around 5 km depth consisting of two subbasins separated by a NE-SW trending local-high ridge. The local high coincides with the magmatic intrusion in geothermal fields and aligns with a series of volcanic bodies’ lineament observed on the surface. We interpret this structural high as a preexisting fault that serves as a magma pathway in the tectonomagmatic interaction. Shallow low-magnitude seismicity in the southern Garut area tends to occur in the resistive bodies. We interpret that heat from the cooling magmatic intrusion may decrease the effective fault-normal stress of the rocks, leading to a decrease in fault failure resistance and may initiate rupture. The resistivity structure around the initial rupture may affect whether or not the nucleation will end up as a large-magnitude earthquake. Furthermore, the unconsolidated young volcanic cover in this area could amplify ground shaking when earthquake occurs that might lead to more extensive damage.
{"title":"Magnetotellurics (MT) and Gravity Study of a Possible Active Fault in Southern Garut, West Java, Indonesia","authors":"I. Arisbaya, Edy Wijanarko, Warsa, P. Sumintadireja, Y. Sudrajat, L. Handayani, M. Mukti, H. Grandis","doi":"10.1155/2023/4482074","DOIUrl":"https://doi.org/10.1155/2023/4482074","url":null,"abstract":"In recent years, dozen low-intensity earthquakes occurred in southern Garut, West Java Indonesia; two of them were reported destructive. However, those shallow earthquake clusters are hardly associated with well-known active faults in the area. Hence, we conducted 3D gravity combined with 2D magnetotellurics (MT) inversions to study the subsurface. Gravity and MT modeling confirm a basin with around 5 km depth consisting of two subbasins separated by a NE-SW trending local-high ridge. The local high coincides with the magmatic intrusion in geothermal fields and aligns with a series of volcanic bodies’ lineament observed on the surface. We interpret this structural high as a preexisting fault that serves as a magma pathway in the tectonomagmatic interaction. Shallow low-magnitude seismicity in the southern Garut area tends to occur in the resistive bodies. We interpret that heat from the cooling magmatic intrusion may decrease the effective fault-normal stress of the rocks, leading to a decrease in fault failure resistance and may initiate rupture. The resistivity structure around the initial rupture may affect whether or not the nucleation will end up as a large-magnitude earthquake. Furthermore, the unconsolidated young volcanic cover in this area could amplify ground shaking when earthquake occurs that might lead to more extensive damage.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2023-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49203420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. E. Nkoungou, S. Tsala, V. Oyoa, P. Eba'a Owoutou
With the properties of laterites being related to the nature of the rock from which they are derived, twenty vertical electrical surveys and twenty boreholes for geotechnical tests, distributed in two units (plutonic and green belt zones) of the Ntem complex located at the northern limit of the Congo Craton, were implemented to study the formation process of the laterites of this geological structure. The inversion of the geoelectrical data in the plutonic area resulted in three lateritic layers with resistivities of 1090 Ω·m, 1302 Ω·m, and 1122 Ω·m, with induration and leaching indices of 28.9% and 72.56%. In the green belt zone, three lateritic layers were also identified with resistivities of 1080 Ω·m, 943 Ω·m, and 1158 Ω·m, with induration and leaching indices of 28.8% and 72.55%. The similarities of the geomechanical parameters (induration and lixiviation indices) show that these soils experienced similar weathering patterns during the same geological period, confirmed by CBR values, corresponding to PF3 platforms that can be used in road works. However, the average resistivity values in the different geological units (1171.77 Ω·m and 1061.16 Ω·m in plutonic and green belt areas) reflect the observed differences in resistivity values of the bedrock alterations (3413.51 Ω·m and 1569.32 Ω·m in plutonic and green belt areas), showing that these laterites are derived from different bedrock weathering. In addition, the average permeability values obtained in the plutonic zone ( k = 6.24 E − 05 cm/s) and in the green belt zone ( k = 5.82 E − 05 cm/s) confirm this difference. The reduction in the difference between the resistivities of the laterites compared to the difference observed in the bedrock of the two units highlights the leaching process over a long geological period.
{"title":"Laterization Process Recognition along the Northern Border of the Congo Craton by Geoelectrical and Geotechnical Data","authors":"H. E. Nkoungou, S. Tsala, V. Oyoa, P. Eba'a Owoutou","doi":"10.1155/2023/8534774","DOIUrl":"https://doi.org/10.1155/2023/8534774","url":null,"abstract":"With the properties of laterites being related to the nature of the rock from which they are derived, twenty vertical electrical surveys and twenty boreholes for geotechnical tests, distributed in two units (plutonic and green belt zones) of the Ntem complex located at the northern limit of the Congo Craton, were implemented to study the formation process of the laterites of this geological structure. The inversion of the geoelectrical data in the plutonic area resulted in three lateritic layers with resistivities of 1090 Ω·m, 1302 Ω·m, and 1122 Ω·m, with induration and leaching indices of 28.9% and 72.56%. In the green belt zone, three lateritic layers were also identified with resistivities of 1080 Ω·m, 943 Ω·m, and 1158 Ω·m, with induration and leaching indices of 28.8% and 72.55%. The similarities of the geomechanical parameters (induration and lixiviation indices) show that these soils experienced similar weathering patterns during the same geological period, confirmed by CBR values, corresponding to PF3 platforms that can be used in road works. However, the average resistivity values in the different geological units (1171.77 Ω·m and 1061.16 Ω·m in plutonic and green belt areas) reflect the observed differences in resistivity values of the bedrock alterations (3413.51 Ω·m and 1569.32 Ω·m in plutonic and green belt areas), showing that these laterites are derived from different bedrock weathering. In addition, the average permeability values obtained in the plutonic zone (\u0000 \u0000 k\u0000 =\u0000 6.24\u0000 E\u0000 −\u0000 05\u0000 \u0000 cm/s) and in the green belt zone (\u0000 \u0000 k\u0000 =\u0000 5.82\u0000 E\u0000 −\u0000 05\u0000 \u0000 cm/s) confirm this difference. The reduction in the difference between the resistivities of the laterites compared to the difference observed in the bedrock of the two units highlights the leaching process over a long geological period.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2023-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42371603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kai Kordelin, J. Virkki, Jaana Kordelin, Juhani Norokallio, Jari Heikkinen, J. Liimatainen, L. Ukkonen, L. Sydänheimo
This research work is aimed at studying different rock types and the effect of their mineral contents on an active 434 MHz RFID card’s radio signal attenuation. This research was done at the ONKALO nuclear waste storage facility using radio frequency identification (RFID) equipment. First, the studied area and research plan, including the used system and equipment, are explained. After this, the researched areas of rock types and their effects on radio signals are presented. This work focused mainly on occupational safety, but it also investigated whether it would be possible to use RFID technology in producing mines as well, especially in the boundary layer of the ore body. This research can help the design of communication frequencies for autonomous devices.
{"title":"Rock Type Effects on Radio Signal Attenuation","authors":"Kai Kordelin, J. Virkki, Jaana Kordelin, Juhani Norokallio, Jari Heikkinen, J. Liimatainen, L. Ukkonen, L. Sydänheimo","doi":"10.1155/2023/1209844","DOIUrl":"https://doi.org/10.1155/2023/1209844","url":null,"abstract":"This research work is aimed at studying different rock types and the effect of their mineral contents on an active 434 MHz RFID card’s radio signal attenuation. This research was done at the ONKALO nuclear waste storage facility using radio frequency identification (RFID) equipment. First, the studied area and research plan, including the used system and equipment, are explained. After this, the researched areas of rock types and their effects on radio signals are presented. This work focused mainly on occupational safety, but it also investigated whether it would be possible to use RFID technology in producing mines as well, especially in the boundary layer of the ore body. This research can help the design of communication frequencies for autonomous devices.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42894096","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The assumption of a homogeneous elastic half-space model is widely used to model the earth’s deformation. However, the homogeneous assumption would not accurately reflect the complexity of the shallow crust. We performed a 3D coseismic deformation model using the finite element method and referred to the 2010 Mentawai earthquake. The 2010 tsunami earthquake was located at the Mentawai segment, which is a part of the accretionary wedge in the Sumatra subduction zone. This active accretionary wedge is identified as the most complicated structure on earth and lies along the Sumatra subduction zone, at which most destructive earthquakes happen in this region. We examined the impact of the accretionary wedge geometry and material properties by considering the wedge as a single different property separated from the continental plate. Various geometrical features, such as topography and wedge dimension, as well as physical properties, were simulated. Those features are then observed for their responses on the surface deformation. The topography affected the magnitude of the horizontal deformation up to 10% but only the pattern of the vertical deformation. The wedge dimension seems to have an insignificant influence on the surface deformation compared to the topography. Different physical properties of the accretionary wedge affect not only the magnitude of the horizontal deformation up to 40% but also the orientation. The direction of the lateral movement is seemingly affected by the material under the GPS station and by the source. On the other hand, the variations in the physical properties resulted in discrepancies of 0.5 meters in the vertical deformation near the source. These results indicated that regional physical property information and geometrical features are critical in estimating coseismic deformation, leading to more accurate slip inversion and earthquake and tsunami hazard prediction, particularly in regions with significant inhomogeneity.
{"title":"Coseismic Deformation Responses due to Geometrical Structure and Heterogeneity of the Accretionary Wedge: Study Case 2010 Mentawai Earthquake, West Sumatra, Indonesia","authors":"Alvina K. Kuncoro, W. Srigutomo, U. Fauzi","doi":"10.1155/2023/5507264","DOIUrl":"https://doi.org/10.1155/2023/5507264","url":null,"abstract":"The assumption of a homogeneous elastic half-space model is widely used to model the earth’s deformation. However, the homogeneous assumption would not accurately reflect the complexity of the shallow crust. We performed a 3D coseismic deformation model using the finite element method and referred to the 2010 Mentawai earthquake. The 2010 tsunami earthquake was located at the Mentawai segment, which is a part of the accretionary wedge in the Sumatra subduction zone. This active accretionary wedge is identified as the most complicated structure on earth and lies along the Sumatra subduction zone, at which most destructive earthquakes happen in this region. We examined the impact of the accretionary wedge geometry and material properties by considering the wedge as a single different property separated from the continental plate. Various geometrical features, such as topography and wedge dimension, as well as physical properties, were simulated. Those features are then observed for their responses on the surface deformation. The topography affected the magnitude of the horizontal deformation up to 10% but only the pattern of the vertical deformation. The wedge dimension seems to have an insignificant influence on the surface deformation compared to the topography. Different physical properties of the accretionary wedge affect not only the magnitude of the horizontal deformation up to 40% but also the orientation. The direction of the lateral movement is seemingly affected by the material under the GPS station and by the source. On the other hand, the variations in the physical properties resulted in discrepancies of 0.5 meters in the vertical deformation near the source. These results indicated that regional physical property information and geometrical features are critical in estimating coseismic deformation, leading to more accurate slip inversion and earthquake and tsunami hazard prediction, particularly in regions with significant inhomogeneity.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2023-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47600025","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Ponomarev, M. Kadyrov, Y. V. Vaganov, Valeria A. Cheymetova, V. Aleksandrov, Aleksandr V. Morev
This review paper presents controversial issues on the formation of hydrocarbon deposits. We look into the geological contradictions of the abiogenic and biogenic theories of petroleum origin, indicating the connection between hydrocarbon deposits and disjunctive dislocations, as well as present disputes about the geological period over which hydrocarbon deposits have been formed. We further overviewed the radical chain mechanism of hydrocarbon generation from organic matter as proposed by Prof. Nesterov. It is noted that the petroleum generation process in reservoir conditions occurs almost instantly in the presence of discrete geomagnetic fields and does not require a long geological time. This is explained by spin magnetic effects (spin catalysis, magnetic isotope properties). We briefly highlight the effect of magnetic fields on chemical reactions involving organic compounds and the use of magnetic fields to enhance oil recovery. We also present the leading causes of discrete magnetic fields in the sedimentary cover: Earth’s geomagnetic reversals, generation of ferromagnetic minerals in oil deposits, electromechanical effects of rock friction near faults, and intermixing of reservoir waters with different mineralization (spontaneous ion polarization). Based on the material reported, we conclude that the radical chain mechanism of petroleum generation processes explains some contradictions of the abiogenic and biogenic theories of petroleum origin. Elaborating this research area has excellent prospects for developing new criteria for hydrocarbon prospecting and devising innovative methods to enhance the oil recovery for shale oil production.
{"title":"Controversial Issues of Hydrocarbon Field Formation and the Role of Geomagnetic Fields","authors":"A. Ponomarev, M. Kadyrov, Y. V. Vaganov, Valeria A. Cheymetova, V. Aleksandrov, Aleksandr V. Morev","doi":"10.1155/2022/2834990","DOIUrl":"https://doi.org/10.1155/2022/2834990","url":null,"abstract":"This review paper presents controversial issues on the formation of hydrocarbon deposits. We look into the geological contradictions of the abiogenic and biogenic theories of petroleum origin, indicating the connection between hydrocarbon deposits and disjunctive dislocations, as well as present disputes about the geological period over which hydrocarbon deposits have been formed. We further overviewed the radical chain mechanism of hydrocarbon generation from organic matter as proposed by Prof. Nesterov. It is noted that the petroleum generation process in reservoir conditions occurs almost instantly in the presence of discrete geomagnetic fields and does not require a long geological time. This is explained by spin magnetic effects (spin catalysis, magnetic isotope properties). We briefly highlight the effect of magnetic fields on chemical reactions involving organic compounds and the use of magnetic fields to enhance oil recovery. We also present the leading causes of discrete magnetic fields in the sedimentary cover: Earth’s geomagnetic reversals, generation of ferromagnetic minerals in oil deposits, electromechanical effects of rock friction near faults, and intermixing of reservoir waters with different mineralization (spontaneous ion polarization). Based on the material reported, we conclude that the radical chain mechanism of petroleum generation processes explains some contradictions of the abiogenic and biogenic theories of petroleum origin. Elaborating this research area has excellent prospects for developing new criteria for hydrocarbon prospecting and devising innovative methods to enhance the oil recovery for shale oil production.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47254973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Site characterization is a prerequisite for the successful and economic design of engineering structures and earthworks by providing geological information for any proposed project. Until now, no detail study has been carried out on the site characterization and classification using shear wave velocity (Vs) up to the top 30 m depth in Hawassa town. For this study, multichannel analysis of surface waves (MASW) was used to determine the variation of Vs for a proper civil engineering design in the town. In addition, vertical electrical sounding (VES) and standard penetration test (SPT) were employed to characterize the near-surface materials. The Vs30 map was prepared for Hawassa town using the estimated Vs30 values which ranges from 248.9 m/s to 371.3 m/s while the SPT-N values were ranges from 5bpf to 50bpf. The correlation of Vs and SPT-N values has been done by considering both corrected and uncorrected SPT-N values. The VES result showed that groundwater is found at a shallow depth. The correlation of Vs and SPT-N value was validated using regression model. The 1D Vs profile and 2D cross-section showed low Vs at a shallow depth. The near-surface soils of the town are classified based on the Vs30 as site class C (stiff soil and soft rock) and D class (stiff soils) according to the NEHRP (Natural Earthquake hazards Reduction Program) and as subsoil classes B and C according to the Eurocode 8. The geotechnical tests also showed that the soils in the study area are silty sand, sand and silty sand with some gravel. The low Vs values observed at a shallow depth should be given much attention during foundation design for the stability of civil engineering structures.
{"title":"Multichannel Analysis of Surface Waves (MASW) to Estimate the Shear Wave Velocity for Engineering Characterization of Soils at Hawassa Town, Southern Ethiopia","authors":"A. Ayele, Kifle Woldearegay, M. Meten","doi":"10.1155/2022/7588306","DOIUrl":"https://doi.org/10.1155/2022/7588306","url":null,"abstract":"Site characterization is a prerequisite for the successful and economic design of engineering structures and earthworks by providing geological information for any proposed project. Until now, no detail study has been carried out on the site characterization and classification using shear wave velocity (Vs) up to the top 30 m depth in Hawassa town. For this study, multichannel analysis of surface waves (MASW) was used to determine the variation of Vs for a proper civil engineering design in the town. In addition, vertical electrical sounding (VES) and standard penetration test (SPT) were employed to characterize the near-surface materials. The Vs30 map was prepared for Hawassa town using the estimated Vs30 values which ranges from 248.9 m/s to 371.3 m/s while the SPT-N values were ranges from 5bpf to 50bpf. The correlation of Vs and SPT-N values has been done by considering both corrected and uncorrected SPT-N values. The VES result showed that groundwater is found at a shallow depth. The correlation of Vs and SPT-N value was validated using regression model. The 1D Vs profile and 2D cross-section showed low Vs at a shallow depth. The near-surface soils of the town are classified based on the Vs30 as site class C (stiff soil and soft rock) and D class (stiff soils) according to the NEHRP (Natural Earthquake hazards Reduction Program) and as subsoil classes B and C according to the Eurocode 8. The geotechnical tests also showed that the soils in the study area are silty sand, sand and silty sand with some gravel. The low Vs values observed at a shallow depth should be given much attention during foundation design for the stability of civil engineering structures.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48057709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Shengelia, N. Jorjiashvili, T. Godoladze, I. Gunia, D. Akubardia
The frequency-dependent parameters of attenuation of P and S waves in one of the most seismically active regions, of the Javakheti plateau, have been estimated using digital data for the first time. We have analyzed and processed hundred and fifty local shallow earthquakes that occurred from 2006 to 2018 and were recorded by five seismic stations. The quality factors for P waves () and for S waves () were evaluated by means of the extended coda normalization method. The obtained and are strongly frequency dependent in the frequency range of 1.5 to 24 Hz, and increase with frequency according to the following power laws:
首次使用数字数据估计了地震最活跃地区之一Javakheti高原P波和S波衰减的频率相关参数。我们分析和处理了2006年至2018年发生的150次局部浅层地震，这些地震由五个地震台记录。P波（Qp）和S波的质量因子（Q s）通过扩展尾段归一化方法进行评估。获得的Q p和Qs在1.5到24的频率范围内强烈依赖于频率 Hz，并根据以下幂律随频率增加：Q P=17.4±2.3 f 1.100±0.033Q S=28.8±3.3 f 1.048±0.039。观察到的Q s/Qp 在整个频率范围内，该比率大于1，这表明散射可能在Javakheti高原上体波的衰减中起主要作用。S波的频率依赖性与格鲁吉亚另一个地震活跃地区Racha地区的剪切波的频率依存性非常相似。
{"title":"Attenuation of P and S Waves in the Javakheti Plateau, Georgia (Sakartvelo)","authors":"I. Shengelia, N. Jorjiashvili, T. Godoladze, I. Gunia, D. Akubardia","doi":"10.1155/2022/4436598","DOIUrl":"https://doi.org/10.1155/2022/4436598","url":null,"abstract":"<jats:p>The frequency-dependent parameters of attenuation of P and S waves in one of the most seismically active regions, of the Javakheti plateau, have been estimated using digital data for the first time. We have analyzed and processed hundred and fifty local shallow earthquakes that occurred from 2006 to 2018 and were recorded by five seismic stations. The quality factors for P waves (<jats:inline-formula>\u0000 <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M1\">\u0000 <msub>\u0000 <mrow>\u0000 <mi>Q</mi>\u0000 </mrow>\u0000 <mrow>\u0000 <mi>p</mi>\u0000 </mrow>\u0000 </msub>\u0000 </math>\u0000 </jats:inline-formula>) and for S waves (<jats:inline-formula>\u0000 <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M2\">\u0000 <msub>\u0000 <mrow>\u0000 <mi>Q</mi>\u0000 </mrow>\u0000 <mrow>\u0000 <mi>s</mi>\u0000 </mrow>\u0000 </msub>\u0000 </math>\u0000 </jats:inline-formula>) were evaluated by means of the extended coda normalization method. The obtained <jats:inline-formula>\u0000 <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M3\">\u0000 <msub>\u0000 <mrow>\u0000 <mi>Q</mi>\u0000 </mrow>\u0000 <mrow>\u0000 <mi>p</mi>\u0000 </mrow>\u0000 </msub>\u0000 </math>\u0000 </jats:inline-formula> and <jats:inline-formula>\u0000 <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M4\">\u0000 <msub>\u0000 <mrow>\u0000 <mi>Q</mi>\u0000 </mrow>\u0000 <mrow>\u0000 <mi>s</mi>\u0000 </mrow>\u0000 </msub>\u0000 </math>\u0000 </jats:inline-formula> are strongly frequency dependent in the frequency range of 1.5 to 24 Hz, and increase with frequency according to the following power laws: <jats:inline-formula>\u0000 <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M5\">\u0000 <msub>\u0000 <mrow>\u0000 <mi>Q</mi>\u0000 </mrow>\u0000 <mrow>\u0000 <mi>P</mi>\u0000 </mrow>\u0000 </msub>\u0000 <mo>=</mo>\u0000 <mfenced open=\"(\" close=\")\">\u0000 <mrow>\u0000 <mn>17.4</mn>\u0000","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45848486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhongxiong Li, Qinru Li, Duorong Zhang, F. Tan, S. Rajaure, Gang Zhao, G. N. Tripathi, Baiwei Du, Ping Yang
Two hundred km of 2D seismic survey was carried out at the Lesser Himalayan Thrust Belts in Dailekh district, western Nepal. The main motivation is to elucidate the geologic relationship between the known oil and gas seeps, subsurface structure, and stratigraphy in the area. This is a challenging task which is from its extreme structural and geological complexity such as thrust faulting, tight folding, steep dip layers, and strong lateral variations in seismic velocity. Seismic data were acquired with SERCEL 428XL system and processed by GEOEAST computer software. In order to increase signal-to-noise ratio (SNR), suppress interference, and search for optimum acquisition parameters, a series of comparative tests on the different charge depth and size, group interval, CDP fold, geophone array, and single high-sensitivity geophone were conducted. We also tested 2S3L (two lines shooting and three lines receiving) wide line profiling. The results indicate that single hole with charge depth of 12 m, 4-16 kg charge size (less charge size for the densely populated areas), single high-sensitivity geophone, and 1S2L wide line profiling with 132 folds are the optimum acquisition parameters. On the basis of comparative process experiment, data processing workflow consisting of data preparation, prestack denoising, amplitude compensation, deconvolution, tomography static correction, velocity analysis, residual static correction, CRS stack, poststack migration, prestack time migration (PSTM), and prestack depth migration (PSDM) was selected. Maybe affected by problem of conflicting dip in complex media, CRS stack section does not show satisfactory geological characteristics. PSTM profile has moderate signal-to-noise (S/N) ratio; the shallow, medium, and deep continuous reflections can be observed in section. More details of the geological structures can be observed in PSDM section, especially in medium and shallow layers (less than 3000 ms or 4000 m), but PSDM method is more expensive and highly time consuming than that of CRS stack and PSTM. So, the PSTM section can be reasonably used for geological interpretation. By reference to field mapping, thrust characteristics, and MT data, the final interpretation to the PSTM section identified the interfaces of 6 geological units (Paleoproterozoic Nabhisthan Fm., Paleoproterozoic Dubidanda Fm., Neogene to Late Cretaceous Surkhet group, Late Carboneferous to Early Cretaeous Gondwana group, Mesoproterozoic Upper Lakharpata group, and Lower Lakharpata group) and delineated Main Boundary Thrust (MBT), Ramgarh Thrust (RMT), Padukasthan Thrust (PT), and Dailekh Thrust (DT). The bottom of Surkhet group which is our top target zone is about 4250 meters deep.
{"title":"Seismic Survey in Lesser Himalayan Thrust Belt, Western Nepal","authors":"Zhongxiong Li, Qinru Li, Duorong Zhang, F. Tan, S. Rajaure, Gang Zhao, G. N. Tripathi, Baiwei Du, Ping Yang","doi":"10.1155/2022/8026088","DOIUrl":"https://doi.org/10.1155/2022/8026088","url":null,"abstract":"Two hundred km of 2D seismic survey was carried out at the Lesser Himalayan Thrust Belts in Dailekh district, western Nepal. The main motivation is to elucidate the geologic relationship between the known oil and gas seeps, subsurface structure, and stratigraphy in the area. This is a challenging task which is from its extreme structural and geological complexity such as thrust faulting, tight folding, steep dip layers, and strong lateral variations in seismic velocity. Seismic data were acquired with SERCEL 428XL system and processed by GEOEAST computer software. In order to increase signal-to-noise ratio (SNR), suppress interference, and search for optimum acquisition parameters, a series of comparative tests on the different charge depth and size, group interval, CDP fold, geophone array, and single high-sensitivity geophone were conducted. We also tested 2S3L (two lines shooting and three lines receiving) wide line profiling. The results indicate that single hole with charge depth of 12 m, 4-16 kg charge size (less charge size for the densely populated areas), single high-sensitivity geophone, and 1S2L wide line profiling with 132 folds are the optimum acquisition parameters. On the basis of comparative process experiment, data processing workflow consisting of data preparation, prestack denoising, amplitude compensation, deconvolution, tomography static correction, velocity analysis, residual static correction, CRS stack, poststack migration, prestack time migration (PSTM), and prestack depth migration (PSDM) was selected. Maybe affected by problem of conflicting dip in complex media, CRS stack section does not show satisfactory geological characteristics. PSTM profile has moderate signal-to-noise (S/N) ratio; the shallow, medium, and deep continuous reflections can be observed in section. More details of the geological structures can be observed in PSDM section, especially in medium and shallow layers (less than 3000 ms or 4000 m), but PSDM method is more expensive and highly time consuming than that of CRS stack and PSTM. So, the PSTM section can be reasonably used for geological interpretation. By reference to field mapping, thrust characteristics, and MT data, the final interpretation to the PSTM section identified the interfaces of 6 geological units (Paleoproterozoic Nabhisthan Fm., Paleoproterozoic Dubidanda Fm., Neogene to Late Cretaceous Surkhet group, Late Carboneferous to Early Cretaeous Gondwana group, Mesoproterozoic Upper Lakharpata group, and Lower Lakharpata group) and delineated Main Boundary Thrust (MBT), Ramgarh Thrust (RMT), Padukasthan Thrust (PT), and Dailekh Thrust (DT). The bottom of Surkhet group which is our top target zone is about 4250 meters deep.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46827028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Njeudjang, Justine Yandjimain, Apollinaire Bouba, Boris Merlain Djousse Kanouo, W. A. Teikeu, N. Djongyang, T. Ndougsa-Mbarga
The study area includes an area between 6° to 8°N and 11° to 15°E. Geologically, it belongs to Precambrian basement (granites, gneisses), Proterozoic, and Archean (volcanic) series, showing the main heat sources of Cameroon. The purpose of this study deals to analyze and interpret the EMAG2 magnetic data in the Adamawa area using various advanced processing techniques. Thus, the mapping and depth estimation of underground structures are realized. The analysis of aeromagnetic map of the reduction to equator (RTE) in Adamawa area reveals rapidly evolving subsurface geological presented its lithological and structural. In the same, the power spectrum-processing tool clearly emphasizes shallow and deep underground heat sources. Two magnetic source location methods (source parameter imaging and analytical signal) are used to characterize of the source. The estimated magnetic source depths from source parameter imaging (SPI) are between 0.3 km and 22 km. The analytical signal ranges from 0.2 km to 31 km. In addition, the comparative study of 2D magnetic modelling showed that the basement is affected by the faults in the main directions of N-S, NE-SW, NW-SE, and WNW-ESE. The resulting structural map based on the tectonic map of Adamawa magnetic basement is a document that can simplify future hydrological and geothermal exploration.
{"title":"Subsurface Tectonic Inferences of the Adamawa Region of Cameroon from EMAG2 Magnetic Data","authors":"K. Njeudjang, Justine Yandjimain, Apollinaire Bouba, Boris Merlain Djousse Kanouo, W. A. Teikeu, N. Djongyang, T. Ndougsa-Mbarga","doi":"10.1155/2022/8451725","DOIUrl":"https://doi.org/10.1155/2022/8451725","url":null,"abstract":"The study area includes an area between 6° to 8°N and 11° to 15°E. Geologically, it belongs to Precambrian basement (granites, gneisses), Proterozoic, and Archean (volcanic) series, showing the main heat sources of Cameroon. The purpose of this study deals to analyze and interpret the EMAG2 magnetic data in the Adamawa area using various advanced processing techniques. Thus, the mapping and depth estimation of underground structures are realized. The analysis of aeromagnetic map of the reduction to equator (RTE) in Adamawa area reveals rapidly evolving subsurface geological presented its lithological and structural. In the same, the power spectrum-processing tool clearly emphasizes shallow and deep underground heat sources. Two magnetic source location methods (source parameter imaging and analytical signal) are used to characterize of the source. The estimated magnetic source depths from source parameter imaging (SPI) are between 0.3 km and 22 km. The analytical signal ranges from 0.2 km to 31 km. In addition, the comparative study of 2D magnetic modelling showed that the basement is affected by the faults in the main directions of N-S, NE-SW, NW-SE, and WNW-ESE. The resulting structural map based on the tectonic map of Adamawa magnetic basement is a document that can simplify future hydrological and geothermal exploration.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45689939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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