Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

Notably, the eastern limit of the Lower Chelif Basin experienced the strongest historical earthquake recorded in North Africa, the 1980 El Asnam earthquake (Mw 7.3). Paradoxically, the Oranie region exhibits lower seismic activity compared to nearby regions. The largest documented historical earthquake occurred in 1790 (Io=IX-X), with significant uncertainties regarding its magnitude and source location due to conflicting historical accounts (Chimouni et al., 2018). While historical records mention additional events of lesser intensity between 1830 and 1960 (Fig. 1b), the instrumental record includes recent moderate earthquakes: two in 2008 (magnitudes 4.8 and 5.5) exhibiting reverse mechanism and one in 2022 (magnitude 4.7) with a strike- slip mechanism. In previous studies, the Oranie region's historical seismicity has been attributed to the Oran-Murdjadjo fault system (Bouhadad, 2001), a prominent structure bordering the northern rim of the Oran basin (Fig. 1b). However, a previously undocumented neotectonic structure, the Arzew Saline Fault-related fold (SARF) traverses the basin's interior and represents a significant geomorphic feature that warrants investigation. (Benbakhti et al., 2018). This study focuses on the Arzew Saline Fault-related fold, aiming to assess its potential contribution to the region's seismic hazard. We analyze the SARF's fold geometry and indicators of recent faulting activity to document its current tectonic behavior. This investigation will improve our understanding of the Oranie region's active tectonics and inform future seismic hazard assessments for this critical coastal zone. M E T H O D O L O G Y A multi-disciplinary approach combining detailed fieldwork, remote sensing analysis, and geomorphic investigations was utilized in this study. Field campaigns targeted key segments of the SARF to establish detailed cross-sections, characterize recent deformations, and map the fold's geometry. Meticulous investigations along the coast identified potential deformations affecting well-preserved Quaternary marine terraces, valuable markers for estimating the most recent folding event and to have a prelimineray first slip rate along the SARF. High-resolution satellite imagery from Google Earth and 12-meter resolution Digital Elevation Model (DEM) derived from Palsar data provided a foundation for field observations and mapping fault scarps and the fold geometry.