Juan Gómez, J. Jaramillo, Mario Saenz, Juan Vergara
A method to study the response of surface topographies submitted to incident waves is presented. The method is based on the superposition of diffracted sources described in Jaramillo et al. (2013). Since the technique proceeds in the frequency domain in terms of the superposition of incident, reflected, and diffracted waves, it has been termed like a superposition based diffraction approach. The final solution resulting from the superposition approach takes the form of a series of infinite terms, where each term corresponds to diffractions of increasing order and of decreasing amplitude generated by the interactions between the geometric singularities of the scatterer. A detailed, step-by-step algorithm to apply the method is presented with regard to the simple problem of scattering by a V-shaped canyon. In order to show the accuracy of the method we compare our time and frequency domain results with those obtained from a direct Green’s function approach. We show that fast solutions with an error of the order of 6.0% are obtained.
{"title":"A Superposition Based Diffraction Technique to Study Site Effects in Earthquake Engineering","authors":"Juan Gómez, J. Jaramillo, Mario Saenz, Juan Vergara","doi":"10.1155/2016/7131867","DOIUrl":"https://doi.org/10.1155/2016/7131867","url":null,"abstract":"A method to study the response of surface topographies submitted to incident waves is presented. The method is based on the superposition of diffracted sources described in Jaramillo et al. (2013). Since the technique proceeds in the frequency domain in terms of the superposition of incident, reflected, and diffracted waves, it has been termed like a superposition based diffraction approach. The final solution resulting from the superposition approach takes the form of a series of infinite terms, where each term corresponds to diffractions of increasing order and of decreasing amplitude generated by the interactions between the geometric singularities of the scatterer. A detailed, step-by-step algorithm to apply the method is presented with regard to the simple problem of scattering by a V-shaped canyon. In order to show the accuracy of the method we compare our time and frequency domain results with those obtained from a direct Green’s function approach. We show that fast solutions with an error of the order of 6.0% are obtained.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":"10 1","pages":"1-14"},"PeriodicalIF":1.1,"publicationDate":"2016-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2016/7131867","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64507556","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}
In April 2015, a M7.8 earthquake occurred less than one month before a M7.3 earthquake near Kodari, Nepal. The Nepal earthquake sequences also include four larger (M > 6) aftershocks. To reveal the interrelation between the main shock and the aftershocks, we check the role of coseismic coulomb stress triggering on aftershocks that follow the M7.8 main shock. Based on the focal mechanisms of the aftershocks and source models of the main shock, the coulomb failure stress changes on both of the focal mechanism nodal planes are calculated. In addition, the coulomb stress changes on the focal sources of each aftershock are also calculated. A large proportion of the M > 6 aftershocks occurred in positive coulomb stress areas triggered by the M7.8 main shock. The secondary triggering effect of the M7.3 aftershock is also found in this paper. More specifically, the M7.3 aftershock promoted failure on the rupture plane of the M6.3 aftershock. Therefore, we may conclude that the majority of larger aftershocks, which accumulated positive coulomb stress changes during the sequence, were promoted or triggered by the main shock failure. It suggests that coulomb stress triggering contributed to the evolution of the Nepal M7.8 earthquake sequence.
{"title":"Study on Coulomb Stress Triggering of the April 2015 M7.8 Nepal Earthquake Sequence","authors":"Jianchao Wu, Qing Hu, Weijie Li, Dongning Lei","doi":"10.1155/2016/7378920","DOIUrl":"https://doi.org/10.1155/2016/7378920","url":null,"abstract":"In April 2015, a M7.8 earthquake occurred less than one month before a M7.3 earthquake near Kodari, Nepal. The Nepal earthquake sequences also include four larger (M > 6) aftershocks. To reveal the interrelation between the main shock and the aftershocks, we check the role of coseismic coulomb stress triggering on aftershocks that follow the M7.8 main shock. Based on the focal mechanisms of the aftershocks and source models of the main shock, the coulomb failure stress changes on both of the focal mechanism nodal planes are calculated. In addition, the coulomb stress changes on the focal sources of each aftershock are also calculated. A large proportion of the M > 6 aftershocks occurred in positive coulomb stress areas triggered by the M7.8 main shock. The secondary triggering effect of the M7.3 aftershock is also found in this paper. More specifically, the M7.3 aftershock promoted failure on the rupture plane of the M6.3 aftershock. Therefore, we may conclude that the majority of larger aftershocks, which accumulated positive coulomb stress changes during the sequence, were promoted or triggered by the main shock failure. It suggests that coulomb stress triggering contributed to the evolution of the Nepal M7.8 earthquake sequence.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":"2016 1","pages":"1-10"},"PeriodicalIF":1.1,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2016/7378920","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64519224","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}
Recently, Luong and Sprik published an article that compared measurements that had been made on 20 samples of saturated rock with a number of empirical models and Glover et al.’s 2012 theoretical model for zeta potential and streaming potential coefficient. They found that none of the empirical models could reproduce the streaming potential coefficient measurements which had been made in the presence of low pore fluid salinities, and the theoretical method could only do so if a constant zeta potential was invoked. This contribution in the form of a comment (i) indicates at least three possible errors in modelling that contribute to the mismatch between the theoretical model and the data at low salinities and (ii) carries out individual modelling on all of samples of Luong and Sprik’s 2014 dataset, showing that Glover et al.’s 2012 theoretical model matches the data well when the zeta potential is allowed to vary and good match can only be obtained with a constant zeta potential if an unrealistic value of zeta potential offset is used.
{"title":"Comment on “Examination of a Theoretical Model of Streaming Potential Coupling Coefficient”","authors":"P. Glover","doi":"10.1155/2015/941246","DOIUrl":"https://doi.org/10.1155/2015/941246","url":null,"abstract":"Recently, Luong and Sprik published an article that compared measurements that had been made on 20 samples of saturated rock with a number of empirical models and Glover et al.’s 2012 theoretical model for zeta potential and streaming potential coefficient. They found that none of the empirical models could reproduce the streaming potential coefficient measurements which had been made in the presence of low pore fluid salinities, and the theoretical method could only do so if a constant zeta potential was invoked. This contribution in the form of a comment (i) indicates at least three possible errors in modelling that contribute to the mismatch between the theoretical model and the data at low salinities and (ii) carries out individual modelling on all of samples of Luong and Sprik’s 2014 dataset, showing that Glover et al.’s 2012 theoretical model matches the data well when the zeta potential is allowed to vary and good match can only be obtained with a constant zeta potential if an unrealistic value of zeta potential offset is used.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":"2015 1","pages":"1-8"},"PeriodicalIF":1.1,"publicationDate":"2015-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2015/941246","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64174259","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}
St. Croix is located inside the sweep of the Lesser Antilles arc and near the southeastern edge of the Greater Antillean ridge. It is separated from the Puerto Rico and the Northern Virgin Islands (PRNVI) block by the Virgin Islands basin. Recent seismic activities demonstrate that the Virgin Islands basin is tectonically active. A better understanding of fault activities in the basin would improve seismic hazard assessment in this region. This study illustrates out a detailed way of deriving relative motion between St. Croix and the PRNVI block using current GPS geodesy infrastructure in the PRVI region. The local geodesy infrastructure includes over 20 continuous GPS stations and a Stable PRNVI Reference Frame (SPRNVIRF). Twenty-year continuous GPS observations (1995–2014) on St. Croix indicate that the island is presently moving away from the PRNVI block toward the southeast (S55°E) at a steady rate of 1.7 mm/year. The velocity vector can be decomposed into two 1.2 mm/year components along the long-axis and short-axis directions of the rhomboidal Virgin Islands basin. Quantitative results indicate that the Virgin Islands basin presently experiences left-lateral motion in a nearly east-west direction and extension in a nearly north-south direction.
{"title":"Relative Motion between St. Croix and the Puerto Rico-Northern Virgin Islands Block Derived from Continuous GPS Observations (1995–2014)","authors":"Hanlin Liu, Guoquan Wang","doi":"10.1155/2015/915753","DOIUrl":"https://doi.org/10.1155/2015/915753","url":null,"abstract":"St. Croix is located inside the sweep of the Lesser Antilles arc and near the southeastern edge of the Greater Antillean ridge. It is separated from the Puerto Rico and the Northern Virgin Islands (PRNVI) block by the Virgin Islands basin. Recent seismic activities demonstrate that the Virgin Islands basin is tectonically active. A better understanding of fault activities in the basin would improve seismic hazard assessment in this region. This study illustrates out a detailed way of deriving relative motion between St. Croix and the PRNVI block using current GPS geodesy infrastructure in the PRVI region. The local geodesy infrastructure includes over 20 continuous GPS stations and a Stable PRNVI Reference Frame (SPRNVIRF). Twenty-year continuous GPS observations (1995–2014) on St. Croix indicate that the island is presently moving away from the PRNVI block toward the southeast (S55°E) at a steady rate of 1.7 mm/year. The velocity vector can be decomposed into two 1.2 mm/year components along the long-axis and short-axis directions of the rhomboidal Virgin Islands basin. Quantitative results indicate that the Virgin Islands basin presently experiences left-lateral motion in a nearly east-west direction and extension in a nearly north-south direction.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":"45 1","pages":"1-9"},"PeriodicalIF":1.1,"publicationDate":"2015-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2015/915753","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64158096","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 Pliocene Sajau coals of the Berau Basin area have a moderately to highly developed cleat system. Mostly the cleat fractures are well developed in both bright and dull bands, and these cleats are generally inclined or perpendicular to the bedding planes of the seam. The presence of cleat networks/fractures in coal seam is the important point in coalbed methane prospect. The 3D X-ray computed tomography (CT) technique was performed to identify cleats characteristics in the Sajau coal seams, such as the direction of coal cleats, geometry of cleat, and cleats mineralization. By CT scan imaging technique two different types of natural fractures observed in Sajau coals have been identified, that is, face cleats and butt cleats. This technique also identified the direction of face cleats and butt cleats as shown in the resulting 3D images. Based on the images, face cleats show a NNE-SSW direction while butt cleats have a NW-SE direction. The crosscutting relationship indicated that NNE-SSW cleats were formed earlier than NW-SE cleats. The procedure also identified the types of minerals that filled the cleats apertures. Based on their density, the minerals are categorized as follows: very high density minerals (pyrite), high density minerals (anastase), and low density minerals (kaolinite, calcite) were identified filling the cleats aperture.
{"title":"X-Ray Computed Tomography Analysis of Sajau Coal, Berau Basin, Indonesia: 3D Imaging of Cleat and Microcleat Characteristics","authors":"A. Hamdani","doi":"10.1155/2015/415769","DOIUrl":"https://doi.org/10.1155/2015/415769","url":null,"abstract":"The Pliocene Sajau coals of the Berau Basin area have a moderately to highly developed cleat system. Mostly the cleat fractures are well developed in both bright and dull bands, and these cleats are generally inclined or perpendicular to the bedding planes of the seam. The presence of cleat networks/fractures in coal seam is the important point in coalbed methane prospect. The 3D X-ray computed tomography (CT) technique was performed to identify cleats characteristics in the Sajau coal seams, such as the direction of coal cleats, geometry of cleat, and cleats mineralization. By CT scan imaging technique two different types of natural fractures observed in Sajau coals have been identified, that is, face cleats and butt cleats. This technique also identified the direction of face cleats and butt cleats as shown in the resulting 3D images. Based on the images, face cleats show a NNE-SSW direction while butt cleats have a NW-SE direction. The crosscutting relationship indicated that NNE-SSW cleats were formed earlier than NW-SE cleats. The procedure also identified the types of minerals that filled the cleats apertures. Based on their density, the minerals are categorized as follows: very high density minerals (pyrite), high density minerals (anastase), and low density minerals (kaolinite, calcite) were identified filling the cleats aperture.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":"2015 1","pages":"1-8"},"PeriodicalIF":1.1,"publicationDate":"2015-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2015/415769","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64954658","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 recently verified superrotation of Earth’s inner core is examined and a new model is presented which is based on the tidal despinning of the mantle and the viscosity of the outer core. The model also takes into account other damping mechanisms arising from the inner core superrotation such as magnetic and gravitational coupling as well as contribution from eddy viscosity in the outer core. The effective viscosity obtained in this model confirms a previously well constrained value of about 103 Pa s. In addition, the model shows that the currently measured superrotation of the inner core must be almost exactly equal to its asymptotic or steady-state value. The effect of extraterrestrial impacts is also investigated, and it is shown that perturbations due to such impacts can only persist over a short geological time.
对最近证实的地球内核的超自转进行了检验，并提出了一个基于地幔的潮汐沉降和外核的黏性的新模型。该模型还考虑了由内核超旋转引起的其他阻尼机制，如磁和引力耦合以及外核涡流粘度的贡献。该模型得到的有效粘度证实了先前良好约束的值约为103 Pa s。此外，该模型表明，当前测量的内核超旋转必须几乎完全等于其渐近或稳态值。还研究了地外撞击的影响，结果表明，这种撞击引起的扰动只能持续很短的地质时间。
{"title":"Superrotation of Earth’s Inner Core, Extraterrestrial Impacts, and the Effective Viscosity of Outer Core","authors":"P. Mohazzabi, J. Skalbeck","doi":"10.1155/2015/763716","DOIUrl":"https://doi.org/10.1155/2015/763716","url":null,"abstract":"The recently verified superrotation of Earth’s inner core is examined and a new model is presented which is based on the tidal despinning of the mantle and the viscosity of the outer core. The model also takes into account other damping mechanisms arising from the inner core superrotation such as magnetic and gravitational coupling as well as contribution from eddy viscosity in the outer core. The effective viscosity obtained in this model confirms a previously well constrained value of about 103 Pa s. In addition, the model shows that the currently measured superrotation of the inner core must be almost exactly equal to its asymptotic or steady-state value. The effect of extraterrestrial impacts is also investigated, and it is shown that perturbations due to such impacts can only persist over a short geological time.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":"2015 1","pages":"1-8"},"PeriodicalIF":1.1,"publicationDate":"2015-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2015/763716","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"65142493","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}
Soft computing based geoelectrical data inversion differs from conventional computing in fixing the uncertainty problems. It is tractable, robust, efficient, and inexpensive. In this paper, fuzzy logic clustering methods are used in the inversion of geoelectrical resistivity data. In order to characterize the subsurface features of the earth one should rely on the true field oriented data validation. This paper supports the field data obtained from the published results and also plays a crucial role in making an interdisciplinary approach to solve complex problems. Three clustering algorithms of fuzzy logic, namely, fuzzy -means clustering, fuzzy -means clustering, and fuzzy subtractive clustering, were analyzed with the help of fuzzy inference system (FIS) training on synthetic data. Here in this approach, graphical user interface (GUI) was developed with the integration of three algorithms and the input data (AB/2 and apparent resistivity), while importing will process each algorithm and interpret the layer model parameters (true resistivity and depth). A complete overview on the three above said algorithms is presented in the text. It is understood from the results that fuzzy logic subtractive clustering algorithm gives more reliable results and shows efficacy of soft computing tools in the inversion of geoelectrical resistivity data.
{"title":"Geoelectrical Data Inversion by Clustering Techniques of Fuzzy Logic to Estimate the Subsurface Layer Model","authors":"A. Raj, D. Oliver, Y. Srinivas","doi":"10.1155/2015/134834","DOIUrl":"https://doi.org/10.1155/2015/134834","url":null,"abstract":"Soft computing based geoelectrical data inversion differs from conventional computing in fixing the uncertainty problems. It is tractable, robust, efficient, and inexpensive. In this paper, fuzzy logic clustering methods are used in the inversion of geoelectrical resistivity data. In order to characterize the subsurface features of the earth one should rely on the true field oriented data validation. This paper supports the field data obtained from the published results and also plays a crucial role in making an interdisciplinary approach to solve complex problems. Three clustering algorithms of fuzzy logic, namely, fuzzy -means clustering, fuzzy -means clustering, and fuzzy subtractive clustering, were analyzed with the help of fuzzy inference system (FIS) training on synthetic data. Here in this approach, graphical user interface (GUI) was developed with the integration of three algorithms and the input data (AB/2 and apparent resistivity), while importing will process each algorithm and interpret the layer model parameters (true resistivity and depth). A complete overview on the three above said algorithms is presented in the text. It is understood from the results that fuzzy logic subtractive clustering algorithm gives more reliable results and shows efficacy of soft computing tools in the inversion of geoelectrical resistivity data.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":"2015 1","pages":"1-11"},"PeriodicalIF":1.1,"publicationDate":"2015-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2015/134834","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64798044","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}
Ground penetrating radar (GPR) is a nondestructive method allowing the improvement of our knowledge of civil engineering structures. In particular, this method may be a nondestructive efficient tool for dike diagnosis and complete classical geotechnical methods. In this paper, we present GPR observations obtained on an earth embankment (crest and sloped paved revetment) in bad condition and located on the lateral canal of the Loire river (Saint Firmin, 80 km South East of Orleans). These measurements are combined with corings, visual inspection, and permeability logging performed with an updated drilling system, the Permeafor. This survey leads (i) to the detection of decompressed zones associated with leakage areas visible at the foot of the downstream slope and (ii) to the location of potentials voids underneath the paved revetment. This multidisciplinary approach complied with the dike inspection methodology proves its efficiency for the assessment of earth embankments.
{"title":"Detection of Leakage Areas in an Earth Embankment from GPR Measurements and Permeability Logging","authors":"R. Antoine, C. Fauchard, Y. Fargier, E. Durand","doi":"10.1155/2015/610172","DOIUrl":"https://doi.org/10.1155/2015/610172","url":null,"abstract":"Ground penetrating radar (GPR) is a nondestructive method allowing the improvement of our knowledge of \u0000civil engineering structures. In particular, this method may be a nondestructive efficient tool for dike diagnosis \u0000and complete classical geotechnical methods. In this paper, we present GPR observations obtained on an earth \u0000embankment (crest and sloped paved revetment) in bad condition and located on the lateral canal of the Loire \u0000river (Saint Firmin, 80 km South East of Orleans). These measurements are combined with corings, visual \u0000inspection, and permeability logging performed with an updated drilling system, the Permeafor. This survey leads \u0000(i) to the detection of decompressed zones associated with leakage areas visible at the foot of the downstream \u0000slope and (ii) to the location of potentials voids underneath the paved revetment. This multidisciplinary approach \u0000complied with the dike inspection methodology proves its efficiency for the assessment of earth embankments.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":"2015 1","pages":"1-9"},"PeriodicalIF":1.1,"publicationDate":"2015-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2015/610172","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"65056659","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}
This research compared the interpretation results of the Vertical Electrical Sounding data acquired using the conventional Schlumberger and modified Schlumberger arrays with a view to assessing the effectiveness of the modified Schlumberger arrays of vertical electrical sounding as an alternative to the conventional Schlumberger array at sites with space constraint during groundwater exploration. A total of thirty-seven (37) sounding locations were occupied and one hundred (100) sounding data for both conventional Schlumberger and modified Schlumberger arrays were collected across different rock units within Ibadan metropolis, south-western Nigeria, with electrode spacing () ranging from 1 to 75 m. The field data were interpreted qualitatively by curve matching and computer iterative methods. Also, statistical analysis of subsurface units and the coefficient of correlation “” of the statistical plots of the field data shows the relationship between the different arrays. The raw data plot of the different arrays shows significant similarities while statistical analysis of the geo-electric parameters obtained from the different arrays across varied lithologic units show that strong relationships exist between the different field methods. The coefficient of correlation with values ranging from 0.7 to 0.99 implies that a good similarity exists between the different field methods employed in this study. Hence, modified Schlumberger arrays can be said to be a good alternative to the conventional Schlumberger array for groundwater exploration especially in urban settings where space constraint is a major challenge.
{"title":"Efficacy of Hummel (Modified Schlumberger) Arrays of Vertical Electrical Sounding in Groundwater Exploration: Case Study of Parts of Ibadan Metropolis, Southwestern Nigeria","authors":"M. Oladunjoye, S. Jekayinfa","doi":"10.1155/2015/612303","DOIUrl":"https://doi.org/10.1155/2015/612303","url":null,"abstract":"This research compared the interpretation results of the Vertical Electrical Sounding data acquired using the conventional Schlumberger and modified Schlumberger arrays with a view to assessing the effectiveness of the modified Schlumberger arrays of vertical electrical sounding as an alternative to the conventional Schlumberger array at sites with space constraint during groundwater exploration. A total of thirty-seven (37) sounding locations were occupied and one hundred (100) sounding data for both conventional Schlumberger and modified Schlumberger arrays were collected across different rock units within Ibadan metropolis, south-western Nigeria, with electrode spacing () ranging from 1 to 75 m. The field data were interpreted qualitatively by curve matching and computer iterative methods. Also, statistical analysis of subsurface units and the coefficient of correlation “” of the statistical plots of the field data shows the relationship between the different arrays. The raw data plot of the different arrays shows significant similarities while statistical analysis of the geo-electric parameters obtained from the different arrays across varied lithologic units show that strong relationships exist between the different field methods. The coefficient of correlation with values ranging from 0.7 to 0.99 implies that a good similarity exists between the different field methods employed in this study. Hence, modified Schlumberger arrays can be said to be a good alternative to the conventional Schlumberger array for groundwater exploration especially in urban settings where space constraint is a major challenge.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":"2015 1","pages":"1-24"},"PeriodicalIF":1.1,"publicationDate":"2015-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2015/612303","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"65057187","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}
3D geometric modeling has received renewed attention recently, in the context of visual scene understanding. The reservoir geometry of the Baltim fields is described by significant elements, such as thickness, depth maps, and fault planes, resulting from an interpretation based on seismic and well data. Uncertainties affect these elements throughout the entire interpretation process. They have some bearing on the geometric shape and subsequently on the gross reservoir volume (GRV) of the fields. This uncertainty on GRV also impacts volumes of hydrocarbons in place, reserves, and production profiles. Thus, the assessment of geometrical uncertainties is an essential first step in a field study for evaluation, development, and optimization purposes. Seismic data are best integrated with well and reservoir information. A 3D geometric model of the Late Messinian Abu Madi reservoirs in the time and depth domain is used to investigate the influence of the reservoir geometry on the gas entrapment. Important conceptual conclusions about the reservoir system behavior are obtained using this model. The results show that the reservoir shape influences the seismic response of the incised Abu Madi Paleovalley, making it necessary to account for 3D effects in order to obtain accurate results.
{"title":"3D Geometric Modeling of the Abu Madi Reservoirs and Its Implication on the Gas Development in Baltim Area (Offshore Nile Delta, Egypt)","authors":"M. Abdel-Fattah, Ahmed Y. Tawfik","doi":"10.1155/2015/369143","DOIUrl":"https://doi.org/10.1155/2015/369143","url":null,"abstract":"3D geometric modeling has received renewed attention recently, in the context of visual scene understanding. The reservoir geometry of the Baltim fields is described by significant elements, such as thickness, depth maps, and fault planes, resulting from an interpretation based on seismic and well data. Uncertainties affect these elements throughout the entire interpretation process. They have some bearing on the geometric shape and subsequently on the gross reservoir volume (GRV) of the fields. This uncertainty on GRV also impacts volumes of hydrocarbons in place, reserves, and production profiles. Thus, the assessment of geometrical uncertainties is an essential first step in a field study for evaluation, development, and optimization purposes. Seismic data are best integrated with well and reservoir information. A 3D geometric model of the Late Messinian Abu Madi reservoirs in the time and depth domain is used to investigate the influence of the reservoir geometry on the gas entrapment. Important conceptual conclusions about the reservoir system behavior are obtained using this model. The results show that the reservoir shape influences the seismic response of the incised Abu Madi Paleovalley, making it necessary to account for 3D effects in order to obtain accurate results.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":"2015 1","pages":"1-11"},"PeriodicalIF":1.1,"publicationDate":"2015-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1155/2015/369143","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64925146","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：