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

Fig. 6: (a) Google Earth image shows the Arzew Saline Fault-related Fold (SARF) with its topographic profile mirroring the underlying fold structure. Red arrows indicate a well- preserved fault scarp, while black arrows point to a possible remnant of an older, eroded scarp. (b) field-based geological cross-section depicts the subsurface structure of the SARF. C O N C L U S I O N S Our investigation of the Oranie region, Algeria, focused on the previously undocumented Arzew Saline Fault-related Fold (SARF). By integrating fieldwork, remote sensing analysis, and geomorphic investigations, we revealed compelling evidence for ongoing tectonic activity along the SARF. Preserved fault scarps, extrados normal faults affecting Late Pleistocene deposits, and deformed marine terraces all point towards the seismogenic character of this structure. Furthermore, analysis of the fold geometry allowed for the estimation of a preliminary slip rate between 0.7 and 0.9 mm/yr. These findings position the SARF as a more credible source for the region's historical seismicity, including the 1790 Oran earthquake. Given its significant length and the calculated slip rate, the SARF has the potential to generate earthquakes comparable to the destructive El Asnam 1980 event. Future research employing trenching and sample dating techniques could refine the estimated slip rate and further elucidate the seismic potential of this critical coastal zone. This improved understanding of the SARF's activity is crucial for informing regional seismic hazard assessments and mitigating earthquake risks in the Oranie region. A C K N O W L E D G M E N T S This research was funded by CRAAG. We are grateful toCRAAG- Oran for their support, and to colleagues A. Heddar and S. Gharbi for valuable feedback. Chimouni, R., Harbi, A., Hamidatou, M., Kherchouche, R., Sebaï, A., & Boughacha, M. S. (2018). The 1790 Oran earthquake, a seismic event in times of conflict along the Algerian coast: A critical review from western and local source materials. Seismological Research Letters. https://doi.org/10.1785/0220180175 Gourinard, Y. (1958). Recherche sur la géologie du littoral oranais. Service de La Carte Géologique de l’Algérie, 6, 200p. Meghraoui, M., Philip, H., Albarede, F., & Cisternas, A. (1988). Trench investigations through the trace of the 1980 El Asnam thrust fault: Evidence for paleoseismicity. Bulletin of the Seismological Society of America, 78(2), 979–999. https: // doi.org/10.1785/BSSA0780020979 Meghraoui, Mustapha, & Pondrelli, S. (2012). Active faulting and transpression tectonics along the plate boundary in North Africa. Annals of Geophysics, 55(5), 955–967. https: //doi.org/10.4401/ ag-4970 Thomas, G. (1976). Mise en évidence de décrochements dextres Est- Ouest d’âge quaternaire en Algérie nord- occidentale. C.R. Acad. Sc. Paris, t.283(Série D), 893– 896.