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The aim of this paper is to present the geomorphological hazards affecting the city of Tétouan, Morocco. The city is one of the most important urban centres in northern Morocco. Its geographical situation is strongly determined by the fact that in the last centuries it was built on the slopes of two ranges of the Rif Mountains, the Dersa to the North and the Ghorghiz to the South. These slopes relatively abruptly rise above the valley of the river Martil. Leaving the city, the river of only 22 km length flows into the Mediterranean Sea across the relatively wide Martil Plain. Given the geographical and geological setting of this area, heavy precipitation causes several problems during the humid period (November-April). Torrential rainfalls can have devastating effects on the community. Another severe problem lies in the hazard perception by the inhabitants, who lack the necessary information on geomorphic hazards and, as a consequence, keep on building their homes on unstable hillslopes. The working group in which authors participated had the objective to prepare a comprehensive documentation to inform the population on hazards, to make people aware of the vulnerability of the environment they live in.

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Écroulements et mouvements de versants associés au niveau du col de Onsar (Rif, Maroc) dans un contexte géologique de décrochement Résumé Le col de Onsar est un accident morphologique qui sépare les deux tronçons de la chaîne calcaire du Haouz. La nature et l'origine de ce col sont à rattacher à son contexte tectonique et à son évolution géomorphologique récente. Il représente, du fait de l'intense déformation tectonique, un couloir de fragilisation des matériaux qui se traduit par des phénomènes d'instabilité aussi nombreux que variés. Dans ce contexte, un village qui porte le nom du col a connu en 1946 et 1963 des écroulements rocheux entraînant des pertes humaines et matérielles. Le village est bâti sur une ancienne accumulation de blocs et la présence d'indices d'instabilité actuels atteste du risque permanent d'écroulement. Ces événements du village ne sont pas des cas isolés puisqu'un inventaire des mouvements de versants dans les environs du col de Onsar révèle la présence d'une instabilité assez importante, dont l'origine et le mécanisme de mise en place sont à rechercher dans le contexte géologique qui est particulièrement complexe. Mots-clés : mouvements de versant, écroulements, décrochement, col de Onsar, Rif. Rockfalls and associated slope movements in the Onsar pass (Rif, Morroco) in a strike-slip fault geological context

In intraplate tectonic regions characterized by moderate seismic activity, the recognition of active zones of deformation has long been a challenging task (e.g., Landgraf et al., 2017). Like Northern Africa, such regions are generally characterized by low hazard but high risk due to the concentrations highly vulnerable population and/or infrastructures (Moreno et al., 2004). Moreover, when low strain rates are combined with meteorological and anthropogenic overprints, the geomorphic signatures associated with active faults fade away as fault slip rates decrease. Consequently, diagnostic criteria established in areas of high strain rates may not be effectively applied. Furthermore, low-levels of seismic strain induce low displacement rates, which may be distributed over numerous fault segments rather than localized on a single fault. At the regional scale, such a distribution of the tectonic deformation can also obscure the seismogenic potential of any given single structure, as, for example, the La Rouvière Fault reactivation during the 2019 M w 4.9 Le Teil Earthquake (Ritz et al., 2020), in southeastern France, which was previously considered as inactive (Jomard et al., 2017).Part of the peri-Mediterranean Alpine chain surrounding the Alboran Sea, the Rif Mountain belt in Morocco is an area of moderate tectonic activity. Located within the diffuse convergence zone between the Nubia Abstract Located at the southern boundary of the Alpine chain in Morocco, the deformation front of the Southern Rif Mountains is a region of moderate tectonic activity, which makes it a good natural laboratory to understand whether, and how, low compressional strains are located on specific structures. Along the ≈80 km-long left-lateral, transpressive and reverse fault zone that runs at the toe of the Pre-Rif Ridges, an analysis of high-resolution digital topography provides new geomorphic lines of evidence supporting Quaternary activity along, 20 km-long fault segments. The fault zone can be divided into the Meknès and the Fès segments, which are constrained at depth by reactivated, NE-trending basement faults, delimitating paleo-grabens associated with the Late Triassic-Jurassic opening of the Atlantic Ocean. For selected sites, we used in situ-produced 36 Cl, 10 Be, and 26 Al and high-resolution topography to infer the timing of abandonment of fluvial markers, which suggest incision rates on the order of 0.6-2 mm/yr. Given their lengths, scaling laws suggest that the identified fault segments should root at about 7-12 kmdepth, possibly reactivating former basement normal faults and making them potential seismogenic sources capable of generating M w 6+ earthquakes, with return times of the order of several hundreds of years. Our new morphochronological data set confirms that the Southern Rif deformation front is a key structure that may have accommodated most of the lateral extrusion of the Rif between the Nubia and Iberia tectonic plates.Plain Language Summary In Morocco, the population may suffer from the dramatic consequences of ...