Hydrological Evaluation of the Groundwater Potential in the Fractured Karoo Aquifer Using Magnetic and Electrical Resistivity Methods: Case Study of the Balfour Formation, Alice, South Africa

IF 1 Q3 GEOCHEMISTRY & GEOPHYSICS
Gbenga Olamide Adesola, O. Gwavava, Kuiwu Liu
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引用次数: 2

Abstract

The study is aimed at evaluating the groundwater accumulations present in Alice using magnetic and electrical resistivity measurements to examine the trends of structural elements and characterize the groundwater resource for borehole drilling. The magnetic maps show a low magnetic linear structure moving northwest to southeast direction, which may be caused by fractures. The linear high intensities were probably caused by dolerite dykes, while dolerite sills caused broader high-intensity areas. The depth slices show that the near-surface magnetic structures are visible to a depth of about 19 m, and the deep-seated structures are found at a depth of about 31 m, possibly deeper. Twenty-five vertical electrical soundings (VES) of the Schlumberger array were measured with AB/2 varying between 1.5 m and 250 m across the study area. The VES interpretation showed four geoelectric layers composed of HK and HA curve types. The geoelectric layer’s thicknesses are (1) topsoil from 0.4 to 1.8 m, (2) weathered layer from 0.8 to 17.5 m, and (3) weathered/fractured layer from 9.9 to 143.9 m; the third layer could be the productive water-bearing zones, and (4) bedrock layer has an infinite thickness. The layers have resistivity values of 20-5752 Ωm, 3-51 Ωm, 136-352 Ωm, and 44-60428 Ωm, respectively. A correlation of the VES with the borehole log indicated a well-matched result. The magnetic and electrical resistivity surveys provided a detailed subsurface structure and helped identify possible fractures that could act as a passage for groundwater.
利用磁电阻率法对裂缝性Karoo含水层地下水潜力进行水文评价:以南非Alice Balfour地层为例
该研究的目的是利用磁电阻率和电阻率测量来评估Alice地区的地下水积累,以检查结构元素的趋势,并描述钻孔所需地下水资源的特征。地磁图显示低磁线状构造向西北至东南方向移动,可能是由断裂所致。线状强地震可能是由白云岩岩脉引起的,而白云岩岩脉引起的强地震范围更广。深度切片显示,近地表磁性构造在约19 m处可见,深层构造在约31 m处可见,可能更深。斯伦贝谢阵列的25个垂直电测深(VES)在研究区域的AB/2在1.5 m到250 m之间变化。探测结果显示,地电层由HK曲线型和HA曲线型组成。地电层厚度为(1)表层土壤厚度0.4 ~ 1.8 m,(2)风化层厚度0.8 ~ 17.5 m,(3)风化破碎层厚度9.9 ~ 143.9 m;(4)基岩层具有无限厚度。各层电阻率值分别为20-5752 Ωm、3-51 Ωm、136-352 Ωm和44-60428 Ωm。通过与测井资料的对比,得出了非常吻合的结果。磁电阻率和电阻率测量提供了详细的地下结构,并帮助识别可能作为地下水通道的裂缝。
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来源期刊
International Journal of Geophysics
International Journal of Geophysics GEOCHEMISTRY & GEOPHYSICS-
CiteScore
1.50
自引率
0.00%
发文量
12
审稿时长
21 weeks
期刊介绍: International Journal of Geophysics is a peer-reviewed, Open Access journal that publishes original research articles as well as review articles in all areas of theoretical, observational, applied, and computational geophysics.
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