Structure of the Plio-Quaternary Coastal Aquifer (Mediterranean basin, Tunisia): Insights from Gravity and Seismic Analysis

Abstract

This research paper presents an investigation of aquifer structure using a combination of gravity and seismic analyses, calibrated by hydrogeological data. This work illustrates how crucial it is to study geological structures and fault network as preliminary work to understand water and pollutant flow systems and aquifer vulnerability, especially with the increased frequency of drought events and climate change pressures. A Plio-Quaternary coastal northeastern aquifer in Tunisia was chosen as the study case. First, a hydrogeological approach was performed using water wells, and piezometers data shows an important fluctuation in the piezometric level and a notable depression in the piezometric surface observed in the southern part of the study area. Secondly, gravity data were analyzed and calibrated by a seismic profile. The results demonstrate the presence of shallow NE-SW faults less than 300 m under the region's principal wadis as well as deeper faults of varying depths (from 400 m to 2600 m) that influence the basin structure, aquifer geometry, and resulting water flow. The combination of those approaches revealed that the variation of the aquifer thickness, piezometric surface depression zones, and groundwater flow is mainly controlled by the shallow and deep geological structures and their tectonic reactivation.