The Pyrenees have experienced at least seven earthquakes with magnitude M > 5 in the last 400 years. During the last decades, several seismotectonic, neotectonic and paleoseismological studies have focused on identifying the main active structures of the areas experiencing damaging earthquakes. In spite of these studies, the regional stress regime is still discussed and there is no unequivocal seismotectonic model at the scale of the range. In this paper, we first present a revision of the former works on active faults in the Pyrenees, and then we discuss the main results in terms of their neotectonic setting. We have distinguished five neotectonic regions according to their seismicity, faulting style and morphologic evolution: the westernmost Pyrenees, the North Western Pyrenean zone, the Foreland basins, the Lower Thrust Sheets Domain and the Eastern Pyrenees. This review lead us to differentiate the range into two major domains: the High Chain, where active faults are controlled by vertical maximum stresses, and the Low Chain, where horizontal maximum stresses of variable orientation seem to be dominant. We propose that these different stress domains are related to the isostatic rebound in response to either the difference in crustal thickness and/or the distribution of the Plio-Quaternary erosion.

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The southern central Andes foothills are made of imbricate thick‐ and thin‐skinned fold and thrust belts. They were formed during Cretaceous and Miocene compressive periods by successive eastward propagation episodes of the orogenic front. We analyze remnant terraces and alluvial deposits of the Neuquén River and its tributaries to study the Plio‐Quaternary tectonic regime in the southern Neuquén Basin. Topographic profiles of remnant terraces show a crustal‐scale (tens of kilometers) anomaly above the Chihuido South anticline. This anomaly is accompanied by sedimentary aggradations downstream and upstream of the anticline. Another anomaly in the terrace profiles, correlated with a knickpoint in the current Neuquén River, is observed farther east, near Añelo. We interpret these anomalies to be the consequence of a Plio‐Quaternary uplift of the Chihuidos and Añelo anticlines. Folding and surface faulting of Plio‐Quaternary alluvial deposits show that this uplift is concomitant with the reactivation of the Miocene orogenic front and of the predominantly thin‐skinned Agrio fold‐and‐thrust belt. From these data we infer that the southern Neuquén Basin is still shortening under a compressive stress regime and that the Andean orogenic front is migrating farther to the east. Extensional features in the study area correspond mainly to thin‐skinned gravitational gliding, resulting from crustal uplift. Thus, we argue that the tectonic compressive regime is preserved in the southern Neuquén Basin throughout the Plio‐Quaternary, though the slab may have steepened during this period.

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