New insights on active geodynamics of Iberia and Northwestern Africa from seismic stress and geodetic strain-rate fields

Abstract

The convergence between Eurasia and Africa during Alpine orogeny drives complex geodynamic processes, involving multiple crustal blocks. In the Atlantic-Mediterranean transition zone, the geodynamics is controlled by the two main plates, the former Iberian microplate and the Alboran Domain. Nowadays, these crustal domains, composed of continental and oceanic crust of varying ages, show distinct deformation behaviors under the current regional stress regime. Through analysis of an enhanced earthquake focal mechanism catalog and updated GNSS velocity field, we constrained the crustal stress–strain fields with unprecedented resolution. Three key findings emerged. First, the different crustal blocks interacting in the region determine the stress–strain fields along the plate boundary, allowing us to define four sectors: Atlantic, Gibraltar, Alboran, and Algero-Balearic. Second, in the Atlantic sector, stresses are directly transferred between Africa and Eurasia, while westward they are absorbed by the thinned continental crust of the Alboran Domain and the continental margins of the Gibraltar Arc and Tell Cordillera. This framework, combined with the oblique Eurasia-Africa convergence relative to the Southwestern Iberian margin, could facilitate the clockwise rotation of Iberia. Finally, intraplate regions with low horizontal strain-rates still show tectonic activity influenced by regional compression and other geodynamic processes driven by vertical stresses. This study highlights the value of combined grid-based stress and strain-rate field analysis for understanding geodynamic processes in complex plate boundary regions.