Active Coastal Tectonics and Uplifted Marine Terraces of Eastern Algiers: Geomatic Approaches for Plate Convergence and Sea-Level Reconstruction

Abstract

The eastern coast of Algiers represents a tectonically active margin within the African–Eurasian plate convergence zone, where the interplay of seismic deformation and sea-level fluctuations has shaped a series of uplifted marine terraces. These geomorphic markers preserve crucial information for quantifying long-term tectonic uplift, relative sea-level change, and seismic hazard. This study integrates geomatic approaches including high-resolution satellite imagery (SRTM 12.5), Geographic Information Systems (GIS), Global Positioning System (GPS) surveys, and field altimetry to map and analyze marine terraces along the eastern Algiers coastline. The research focuses particularly on the sector affected by the Mw 6.8 Zemmouri earthquake of May 21, 2003, which revealed the strong influence of active coastal tectonics in the region.A total of 81 measurements were conducted during our field investigations, and DEM analysis identified at least two distinct, well-preserved terrace levels. The first terrace, situated between 30.71 and 43 m above sea level, reflects long-term tectonic uplift linked to fault slip rates. The second terrace, preserved between 1 and 8.11 m, records more recent interactions between eustatic sea-level fluctuations and coseismic deformation. These elevations were validated through GPS and altimeter measurements, then cross-compared with regional sea-level curves. Preliminary interpretations suggest that terrace deformation is primarily controlled by active fault systems associated with the African–Eurasian convergence, while superimposed eustatic variations influence terrace morphology and preservation. The combined dataset provides new insights into uplift rates, neotectonic activity, and the spatial variability of deformation along this seismically active margin.By applying geomatic tools to coastal geomorphology, this study reconstructs the relationship between tectonic uplift and sea-level change, offering an improved understanding of long-term seismic hazard and coastal evolution in Algeria. These results contribute to regional geodynamic models, coastal risk assessment, and urban resilience strategies in the Western Mediterranean.