Actividad sísmica en el extremo Occidental de los Pirineos; Seismic activity in the Western Pyrenean edge

Abstract

The moderate magnitude seismicity on the westernmost Pyrenean domain is poorly constrained from the present-day permanent networks monitoring the area because of low station coverage. New seismic data collected from a portable network deployed there for 17 months provide an enhanced image of the seismic activity, revealing clear tectonic implications. Results delineate the westward continuity of the E-W band of seismicity associated to the North Pyrenean Fault, through the Basque Massifs along the Nappe des Marbres, ending up at the Hendaye fault. This seismicity belt is distributed on a crustal scale, dipping northward to almost 30 km depth. Other groups of seismic events located in the area can be related to the southern segment of the Pamplona fault, and to different E-W thrust structures. Portable seismic networks hence appear as valuable tools to constrain tectonic and seismic hazard features in mountainous areas.