Aldeep Mohamed, Soliman Mamdouh, Mesbah Hany S A, Gaweish Wael R, Ali Ahmed M, Meqbel Naser, Zaher Mohamed Abdel
The National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, Cairo, Egypt.
Department of Geoinformatics, Physical and Environmental Geography, University of Szeged, Egyetem U. 2-6., Szeged, 6722, Hungary.
Sci Rep. 2025 Sep 24;15(1):32697. doi: 10.1038/s41598-025-20074-x.
Geological structures are the most critical parameter for understanding the distribution of groundwater, oil, and minerals. In Siwa Oasis and other oases with comparable geological settings in the northern Western Desert, Egypt, brackish groundwater seeps to the surface through fractures and permeable zones, sustaining phreatophytic vegetation and enabling human habitation in otherwise arid environments. The formation of these oases is closely tied to the subsurface structural and hydrogeological conditions. To determine the origin of these lakes, a geophysical investigation was conducted using magnetic and magnetotelluric (MT) data to identify whether the water leakage stems from deeper artesian aquifers or shallower marine-origin reserves. Magnetic data were used for the geological structural analysis and the depth estimation of basement rocks. The Magnetic Data Analysis includes constructing the Total Horizontal Gradient (THG), Tilt Derivative (TDR), and 2D Magnetic Modelling Constrained by borehole data to estimate basement depths. Magnetotelluric (MT) data analysis includes obtaining 3d resistivity models via inversion, and Cross-sections were extracted to trace fault zones and lithological contrasts. The Key Findings from this study are Surface Lineaments that are dominant in the Northeast (NE), North (N), and East-Northeast (ENE), with a minor East-West (E-W) trend. Shallow Trend Analysis (Tilt Derivative-TDR): Revealed structures in NE-SW, NW-SE, and E-W directions. Total Horizontal Gradient (THG) Map: Confirmed major structural trends in NE-SW, NW-SE, and E-W directions, with additional W-NW trends. The E-W trend correlates with most lakes in the study area. Depth estimation (2D magnetic modelling): Basement rock depths range between 3400 and 4600 m in the magnetic data coverage. The magnetotelluric (MT) model reveals a near-surface E-W direction with resistivity variations linked to lithology changes and groundwater presence.
地质构造是了解地下水、石油和矿产分布的最关键参数。在埃及西部沙漠北部的锡瓦绿洲以及其他地质环境类似的绿洲中，微咸水通过裂缝和渗透带渗出地表，维持着适水植物的生长，并使得人类能够在原本干旱的环境中居住。这些绿洲的形成与地下构造和水文地质条件密切相关。为了确定这些湖泊的成因，利用磁法和大地电磁（MT）数据进行了地球物理调查，以确定漏水是源于更深层的自流含水层还是较浅的海相成因储量。磁法数据用于地质构造分析和基底岩石深度估计。磁法数据分析包括构建总水平梯度（THG）、倾斜导数（TDR）以及受钻孔数据约束的二维磁法建模，以估计基底深度。大地电磁（MT）数据分析包括通过反演获得三维电阻率模型，并提取剖面以追踪断层带和岩性对比。本研究的主要发现包括：地表线性构造在东北（NE）、北（N）和东北偏东（ENE）方向占主导，东西（E-W）方向较少。浅层趋势分析（倾斜导数-TDR）：揭示了东北-西南、西北-东南和东西方向的构造。总水平梯度（THG）图：证实了东北-西南、西北-东南和东西方向的主要构造趋势，以及额外的西-西北方向趋势。东西方向趋势与研究区域内的大多数湖泊相关。深度估计（二维磁法建模）：在磁法数据覆盖范围内，基底岩石深度在3400至4600米之间。大地电磁（MT）模型揭示了近地表东西方向，电阻率变化与岩性变化和地下水存在有关。
