Anisotropía de la corteza superior mediante interferometría de ruido sísmico y separación de ondas S (Cordillera Cantábrica, NO España)

Abstract

This study presents the first geophysical measurements of the anisotropic properties of the upper crust (0-10 km) in the central Cantabrian Mountains. For this task, 1 year of continuous seismic data have been analyzed and compared. These datasets come from two temporary networks with different configurations: a) a local (50x50 km) short-period seismic array (Geo- cantábrica Seismic Network) and b) a regional-scale (120x250) broadband network (IberArray and Instituto Geográfico Nacional). In both cases, the networks sample continental crust heavily configured during the Variscan orogeny, however, the intensity of alpine structures differed at the surface. The analysis of the data has been performed with two independent passive seismic methods: a) the azimuthal variation of Rayleigh wave group velocities from ambient noise interferometry and b) the splitting of S waves from local earthquakes. Preliminary results show average anisotropy strengths ranging between 3-10%. Furthermore, a clear correlation between the fast directions obtained from both methods and the orientations of local faults close to the stations is observed. To the west of the study area, fast polarization directions tend to align parallel to the Variscan fabric in the crust, while to the east, where the Alpine imprint is stronger, many fast directions are aligned parallel to E-W oriented Alpine features.