Up to now, dispersion analysis of surface waves across the Iberian Peninsula and adjacent zones has been based on analog data recorded at the long-period Iberian stations. Also, the northern region of the peninsula has never been investigated due to the lack of seismological stations. With the ILIHA data set now available, it is possible to investigate the northern part of Iberia from quality digital records. To efficiently remove higher-mode interference and to improve isolation of the fundamental-mode Rayleigh wave from the seismograms, time-variable filtering is employed. Once the signal is filtered, multiple filtering is then used to compute group velocities at each station. The interstation Rayleigh-wave group velocity can thus be easily calculated. Frequency-domain Wiener deconvolution is used to determine the interstation phase velocity. We carried out inversion of velocity dispersion data containing both Rayleigh-wave phase velocities and group velocities according to the generalized inversion theory by means of the stochastic inverse operator. The theoretical 2-D Earth models determined by joint inversion allow us to obtain for the first time the distribution of the shear-wave velocity both laterally and with depth for the northern Iberian region, and to emphasize the main features of the crust-mantle structure of this area.

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