3D gravity modelling of the basement of the Mitidja Basin (Algeria): Approach and tectonic implications

The modelling of the morphology and depth of the basement of sedimentary basins is essential for various geological and geophysical investigations, including tectonic analysis, hydrogeological studies, and seismic hazard assessment. In this study, a three-step approach was applied to model the crystalline basement of the Mitidja Basin (Algeria) in the absence of borehole or seismic data.

This approach combines energy spectrum analysis to identify characteristic gravity frequencies, optimisation of gravity anomalies from outcrop zones, and 3D inversion based on the Parker-Oldenburg algorithm. It enabled the mapping of the crystalline basement of the Mitidja Basin for the first time, revealing a complex structure influenced by two transverse faults associated with regional tectonics. These dextral and sinistral faults play a key role in the deformation and segmentation of the reverse fault systems that bound the Mitidja Basin to the north and south, a dynamic corroborated by focal mechanisms of recent earthquakes.

The resulting map highlights two distinct parts of the basin, separated by basement uplift in the centre. The observed correlation between the crystalline and Plaisancian basements suggests significant hydraulic potential in areas not covered by geo-electrical surveys, where borehole data could provide confirmation.

This study also emphasises the importance of further seismo-tectonic research in this region, particularly around Algiers, to improve seismic hazard assessment and water resource management.