Onshore and offshore seismotectonics of Iberia: an updated review

Abstract

An analysis of 542 moment tensor focal mechanisms across the Iberian Peninsula was conducted to infer active tectonic deformation and stress regimes. This study employed a suite of complementary methodologies, including focal mechanism classification (FMC) of the rupture type, composed focal mechanisms based on the average seismic moment tensor, rotation angle between tensor estimates, right dihedra composed focal mechanisms, slip model analysis to determine the strain conditions, and classical stress inversión methodology. Based on the slip model results and considering the tectonic constraints of Cenozoic deformation in Iberia, the study region was subdivided into several tectonically coherent zones, where the different methods were applied independently to ensure robust regional interpretations. The results indicate that thrust faulting stress regimes are active in the Gorringe–Horseshoe (GH) area and the easternmost Tell Atlas. In the south, most of the zones are transpressive, as is the southwestern corner of Iberia, south of Lisbon. The exception is the Granada Basin (GB), which exhibits a nearly radial normal faulting stress regime. Normal faulting stresses are dominant in the Pyrenees and the Mediterranean rim, north of the Betic Mountains. In the central part of the Pyrenees, the maximum horizontal extensión is oriented perpendicular to the mountain range, indicating that local stresses related to post-orogenic collapse or isostatic rebound dominate over regional ones. The máximum horizontal compression along the Eurasia–Africa plate limit is consistently oriented around N154° E, except in some parts of the Betics that are probably influenced by a remnant effect of the Alboran Slab. In the Central Ranges and offshore Atlantic, the maximum horizontal compression is slightly rotated anticlockwise to N140° E.