ANISOTROPY BENEATH THE NORTH PYRENEAN FAULT

The anisotropy beneath the North Pyrenean fault, which delineates the boundary between the Eurasian and Iberian plates, is studied from the splitting of SKS- and SKKS-waves recorded at a broad-band station of t he NARS array in the western Pyrenees. Events coming from different az imuths and with different incidences reveal a complex pattern of aniso tropy. It is globally characterized by a fast direction at 105-degrees east from north, parallel to the elongation of the range. Events comi ng from the south give a time delay between the fast and slow directio ns consistent with that obtained in Iberian stations (deltat = 1.0-1.5 s). Most of the events coming from the north give a very large, 2 s, time delay. It is suggested that this strong anisotropy results from t he combined effects of two contributions: one related to the large sca le anisotropy in southern Europe and one related to the specific tecto nics of the Pyrenean range.