A detailed ground magnetic survey was carried out in a basement complex underlain Modomo community in southwestern Nigeria with a view to delineating the subsurface structures, estimate the overburden thicknesses and assess the relevance of the geophysical method in groundwater investigation in the locality. The total field component of the earth’s magnetic field was measured at station intervals of 10–100 m along access routes within the study area. The data were corrected for diurnal variation and offset and subsequently reduced to the magnetic equator (RTE). Data enhancement techniques including the second vertical derivative, total horizontal derivative and Euler deconvolution were applied to the RTE data to map edges and estimate depths to the structures. Overburden thicknesses were estimated from 2D magnetic subsurface modeling along eight profiles. The magnetic survey derived lineaments (structures) and overburden thicknesses were validated with resistivity survey derived 2D structures and overburden thicknesses and borehole log data from the study area. Twenty-four lineaments with lengths ranging from 150 to 777 m were identified from the magnetic map. The lineament orientations were E–W, ENE–WSW, WNW–ESE, NNW–SSE, NW–SE and NE–SW directions. Many of the identified lineaments correlated significantly with structures derived from the 2D resistivity images. Comparable thicknesses were observed between correlated magnetic derived overburden thicknesses (4.41–29.4 m) and depths from wells and boreholes (5.48–27.1 m). The study concluded that the magnetic method could be reliably used for overburden thickness estimation and structure mapping required in groundwater potential assessment in a typical basement complex terrain.

中文翻译：

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磁性方法作为地下复杂地形地下水调查的一种工具：以尼日利亚西南部Modomo为例

在尼日利亚西南部的莫德莫社区地下复杂地层中进行了详细的地磁测量，目的是勾勒出地下结构，估算覆盖层厚度并评估地球物理方法在当地地下水调查中的相关性。沿着研究区域内的进入路线，以10-100 m的站点间隔测量了地球磁场的总场分量。对数据进行昼夜变化和偏移校正，然后减少到磁赤道（RTE）。数据增强技术包括二阶垂直导数，总水平导数和Euler反卷积应用于RTE数据，以绘制边缘并估计结构的深度。根据8个剖面的2D磁性地下模型估算覆盖层厚度。用研究区的电阻率测量二维结构，上覆层厚度和井眼测井数据验证了磁测量得出的地层（结构）和上覆层厚度。从磁图中识别出二十四个线段，长度在150至777 m之间。线条方向为E–W，ENE–WSW，WNW–ESE，NNW–SSE，NW–SE和NE–SW方向。许多已识别的线条与源自2D电阻率图像的结构显着相关。在相关的磁性衍生覆盖层厚度（4.41-29.4 m）与井眼和井眼深度（5.48-27.1 m）之间观察到了可比的厚度。