Mapping the Subsurface Structures in El-Gallaba Plain, Southern Egypt Using Three-Dimensional Geophysical Inversion of Magnetic Data

Abstract:

Water scarcity is becoming a global issue facing sustainable development and threatens human existence. Conventional resources of freshwater are limited and undergoing depletion due to unplanned exploitation. In Egypt, the Nile river is the primary freshwater resource. Still, unfortunately, the water budget in Egypt lacks a water shortage of 13.5 Billion cubic meters per year (BCM/yr) and is expected to increase continuously [1]. Searching for other resources of freshwater is forming a challenge in Egypt. Among promising resources for freshwater, groundwater attains the most interest. El-Gallaba Plain is one of the most promising sites for groundwater exploration due to the ancient water pathways in that area and its suitability for different approaches concerning sustainable development strategies. It covers a large area that limits conventional exploration using drilling. Geophysical exploration helps to locate the underground aquifers and suggests the most suitable locations for borehole drilling. A first step of the groundwater exploration is to map the water bearings subsurface structures.

In this research, we provide the results of magnetic data interpretation to map the subsurface structures. Structural Lineaments were detected using the Analytic signal, tilt angle, and theta map. We calculated the depth to the basement using Source Parameter Image (SPI) and Analytic Signal (AS) techniques. We applied three-dimensional inversion of the magnetic data to map the three-dimensional subsurface distribution of the magnetic susceptibilities. Results show a graben-like structure at the northern part of the plain; it extends from the Nile river at the east trending north-west. The graben has a uniform width of approximately 20 km, it reaches 50 km long, which is the limit of the magnetic data coverage. The maximum depth of the graben reaches 3000 meters. The results of this research are correlated with the tectonic history of the area. These results, along with other available information of the study area, will provide the decision-makers with the necessary information for groundwater exploration and exploitation.

[1] Mohie El Din, M. O., & Moussa, A. M. (2016). Water management in Egypt for facing the future challenges. Journal of advanced research, 7(3), 403-412.

[2] Goudie, A. S. (2005). The drainage of Africa since the Cretaceous. Geomorphology, 67(3-4), 437-456.