Active Tectonics of the Pyrenees: A review Revisión de la tectónica activa de los Pirineos P. Lacan 1,2 , M. Ortuño* 1,3 1 Centro de Geociencias, Universidad Nacional Autónoma de México, Blvd. Juriquilla, 3001, 76230, Juriquilla, Querétaro, Mexico 2 Laboratoire des Fluides Complexes et leurs Réservoirs (LFC-R) UMR5150 - CNRS, Université de Pau, IPRA, BP 1155, F-64013 Pau Cedex, France 3 Departament de Geodinàmica i Geofisica, Universitat de Barcelona, Martí i Franquès s/n, 08028, Barcelona, Spain *Corresponding author: maria_ortuno@geociencias.unam.mx. Tel.: +52 (442) 238-1104 Ext. 104; fax: +52 (442) 238-1124 Received: 05/07/2011 / Accepted: 18/04/2012 Abstract The Pyrenees have experienced at least seven earthquakes with magnitude M > 5 in the last 400 years. During the last decades, se- veral 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 irst 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 ive 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. Keywords: Neotectonics, Seismogenetic sources, Stress ield, Geodynamics, Isostatic compensation of erosion ISSN (print): 1698-6180. ISSN (online): 1886-7995 www.ucm.es/info/estratig/journal.htm Journal of Iberian Geology 38 (1) 2012: 9-30 http://dx.doi.org/10.5209/rev_JIGE.2012.v38.n1.39203