Advances in the knowledge of seismogenetic structures in the eastern edge of the Pyerenees

Abstract

<p><span>Although the seismic activity at the eastern Pyrenees is nowadays moderate and sparse, with </span><span>events usually not exceeding magnitudes 4.5, this area has been affected in the past by the most </span><span>destructive event occurred in the Pyrenees, reaching an intensity of IX, whose seismogenic </span><span>structure is not well  understood and still under debate. In order to progress in the knowledge of </span><span>these structures, we present here the results derived from a 14 months-long broad-band seismic </span><span>deployment focused on the Cerdanya Basin, but encompassing the eastern termination of the </span><span>Pyrenees. The dense station coverage has allowed us to obtain accurate hypocentral locations, as </span><span>well as up to 23 focal mechanisms from local low-magnitude earthquakes. In addition to a </span><span>relatively sparce seismicity, several clusters of seismic events located in well-defined, small areas </span><span>and depth ranges have been identified. The results show a few low-magnitude seismic events </span><span>located in the southern limit of the Cerdanya Basin that could be related to oblique secondary </span><span>faults within the footwall of the Têt Fault, the major tectonic structure in the area. Our data shows </span><span>also that the Capcir Fault has associated seismicity, with some of the events located out of the </span><span>fault plane, perhaps on secondary fault branches. To the east, a cluster of low-magnitude events is </span><span>detected in the epicentral area of two relatively large earthquakes occurred recently, probably </span><span>indicating the development of the preparatory phase. Further west, the Maladeta Massif has a </span><span>sustained seismic activity, although its origin does not seem to be related to the most relevant </span><span>structure in the area, the North Maladeta Fault. Regarding focal mechanisms, most of them show </span><span>normal fault solutions with nodal planes NW-SE oriented, which are in agreement with the </span><span>extensional regime perpendicular to the axis of the chain derived from the seismic and geodesic </span><span>data.</span><br><br></p><div> <div> <div> <div aria-label="Página 1" data-loaded="true"> <div> </div> </div> </div> </div> </div><div></div>