The tectonic framework of Morocco is dominated by the interaction between the African and Eurasian plates. Presently, the Nubian Plate moves in a northwest direction with respect to Eurasia resulting in complex collision and strike-slip faulting from the Atlas and Rif Mountains in Morocco to the Betic Mountains in southern Spain. GPS quantification of active crustal deformation in this western Mediterranean region of slow, oblique Africa-Eurasia plate convergence provides new constraints on the mechanics of plate interactions during the final stage of ocean subduction and the initial stages of continental collision. This study will provide new GPS measurements of plate velocities with reduced uncertainties to test competing tectonic models for this enigmatic slow-moving plate boundary. The project advances desired societal outcomes through development of a globally competitive STEM workforce by training of post-doctoral fellow and Moroccan students, development of international collaborations, and research infrastructure enhancement by expansion of a GPS network.
This research project will provide new observations necessary to constrain geodynamic processes in the western Mediterranean zone of plate interaction, including active translation and rotation of the Alboran Sea and Moroccan Rif, shortening across and vertical motions in the High Atlas, and strike-slip motion in the Betics of southernmost Spain. Resultant geodetic constraints will distinguish between competing tectonic models: 1) westward rollback associated with the Gibraltar Arc; 2) southward rollback of the subducted Nubian plate, and/or 3) delamination of the continental lithosphere within the collision zone. In collaboration with scientists from Morocco (Centre National pour la Recherche Scientifique et Technique, Universite Mohamad V, Abdelmalek Essaadi University), France (Universite Montpellier), and Spain (Real Instituto y Observatorio de la Armada), this research team will refine present geodetic deformation estimates to better constrain geodynamics across the entire zone of plate interaction. The team will reobserve 6 survey sites, reducing velocity uncertainties by 30 to 50% (to about 0.3 mm/year horizontal, 0.7 mm/year vertical). In addition, the team will establish a new continuous GPS station in the Rif where deformation rates are greatest, reaching about 4 mm/year with respect to stable Nubia. Improved velocity determinations are necessary to constrain vertical motions and estimate internal deformation of the Rif, as well as slip rates on Rif bounding structures, information that is essential to constrain better both the mechanics of active deformation and seismic hazards on active faults. GPS survey sites across the the Middle, High, and Anti-Atlas Mountains will be reobserved, which will result in greater than 50% decrease in velocity uncertainties (to less than 0.3 mm/year horizontal, 0.7 mm/year vertical), providing the first geodetic constraints on vertical motion rates and a two-fold improvement on upper bounds on active shortening across the High Atlas. These improved velocities are necessary to better constrain the role of crustal shortening and subcrustal dynamic processes in maintaining the high elevation of the High Atlas Mountains, and the relationship to dynamic processes along the plate boundary. Analysis, interpretation, and modeling will be undertaken jointly with the international collaborators.
