Seismo‐tectonic model for the southern Pre‐Rif border (Northern Morocco): Insights from morphochronology

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 Meknes and the Fes 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 36Cl, 10Be and 26Al 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 km‐depth, possibly reactivating former basement normal faults and making them potential seismogenic sources capable of generating Mw6+ earthquakes, with return times of the order of several hundreds of years. Our new morphochronological dataset 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