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Seismo‐Tectonic Model for the Southern Pre‐Rif Border (Northern Morocco): Insights From Morphochronology
Author(s) -
Agharroud Kamal,
Siame Lionel L.,
Ben Moussa Abdelkhalak,
Bellier Olivier,
Guillou Valéry,
Fleury Jules,
El Kharim Younes
Publication year - 2021
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2020tc006633
Subject(s) - geology , graben , seismology , fault (geology) , tectonics , basement , sinistral and dextral , quaternary , paleontology , transform fault , normal fault , fault block , fault scarp , geomorphology , civil engineering , engineering
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 km‐depth, 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.