Surface Wave Dispersion Measurements from Ambient Seismic Noise Analysis in Italy

We present the surface wave dispersion results of the application of the ambientnoise method to broadband data recorded at 114 stations from the INGV national network and the MedNet network. Vertical-component ambient noise data from October 2005 to March 2007 have been correlated with one another to compute estimated fundamental model Rayleigh wave Green's functions. Cross-correlations are calculated in one- hour segments, stacked over 1.5 yr, and Rayleigh wave group dispersion curves at periods from 7 to 45 s were determined using the multiple-filter analysis technique. The study region was divided into 0.2° × 0.2° to invert for group velocity distributions. Checkerboard tests were first carried out, and the lateral resolution was estimated to be in 0.6°. The resulting group velocity maps from 7 to 45 s showed good correlations with known geological and tectonic features, the signatures of sedimentary basins and crustal thickness are revealed clearly in the maps. The central Alps is clearly resolved with lower group velocities due to thick terrigenous sediments and deep Moho underneath the Alps. Our results also indicate that the Moho depth on the Tyrrhenian side of the northern Apennines is much shallower than the Adriatic side.