Integrated Structural Mapping and Geological Analysis of Megado, Southern Ethiopia using Remote Sensing, Gravity and Magnetic Methods for Groundwater Prospecting

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IJEP 45(10): 871-881 : Vol. 45 Issue. 10 (October 2025)

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Bereket Gebresilassie1, Yeman Gebru1, Shimeles Fisseha2 and N. Rao Cheepurupalli3*

1. Aksum University, Department of Geology, Faculty of Mines, Shire 314, Tigray-Ethiopia
2. Addis Ababa University, Applied Geophysics Unit, Institute of Geophysics, Space Science and Astronomy, Addis Ababa, Ethiopia
3. Aksum University, Department of Mineral Processing and Metallurgical Engineering, Faculty of Mines, Shire 314, Tigray-Ethiopia

Abstract

The Megado area is characterized by hard rock terrain with a Precambrian crystalline basement or suites of intrusive rocks, overlain by tertiary volcanic products, such as basalt, scoria and eluvium deposits. An integrated approach combining remote sensing and potential field data was employed to investigate the geological structures and formations. Landsat 8 OLI imagery, alongwith gravity and magnetic surveys, were utilized. True colour and principal component density maps helped map lineaments from Landsat images. These maps revealed three lineaments trending northwest-southeast (NW-SE). Similarly, both qualitative and quantitative analyses of magnetic and gravity data confirmed the presence of these structural features. Interpretation of magnetic tilt derivative and analytic signal maps indicates that the structural features are oriented along northwest-southeast (NW-SE), northwest-southwest (NW-SW), north-northeast (NNE) and south-southeast (SSE). These various trends suggest that the area has undergone different tectonic cycles. Positive magnetic breaks or gradients reflect underlying basic intrusions and crystalline basement rocks, while negative anomalies are associated with deep structural features affected by weathering and dissolution. The structural features observed in magnetic data correspond with the residual gravity anomaly in the same orientations. Higher gravity anomalies in the residual gravity map indicate zones of higher-density basement rocks, whereas lower values represent thin crustal areas, such as fractures or faults with low density. These fractures are conducive to groundwater occurrence and circulation. Overall, the combined results from these methods indicate that the Megado area has experienced multiple tectonic episodes involving deep structural features.

Keywords

Lineaments, Hard-rock terrain, Gravity and magnetic methods, Semi-arid area, Groundwater

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