Shallow seismic structure of the Iberian Peninsula from ambient noise surface wave tomography

We have obtained group velocity maps of short period Rayleigh waves from 10 to 20 seconds for the Iberian Peninsula by cross-correlating 4 months of ambient noise data recorded by 40 permanent broadband stations in the region. Group velocity maps accurately image the main structural elements of the Iberian upper crust, including the Iberian Massif (the stable Hercynian core), Alpine orogens and major sedimentary basins. The Pyrenees and the Iberian cordillera are imaged as relatively high group velocities, in contrast with the Betic cordillera, which is characterized by low velocities. We explain these anomalies by the presence of widespread intramontane basins created in an extensional episode simultaneous with north-south convergence between the African and Eurasian plates. The most prominent low velocity anomaly in the Iberian Peninsula is related to the Guadalquivir basin and the flysch units of the Campo de Gibraltar, which consist of unmetamorphosed deep-water turbidite deposits from Early Cretaceous to Early Miocene.