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A temporary network of 33 seismic stations was deployed in the area struck by the 6th April 2009, Mw 6.1 (Scognamiglio et al. in Seism Res Lett 6/81, 2010), L’Aquila earthquake (central Italy), with the aim to investigate the site amplification within the Aterno river Valley. The seismograms of 18 earthquakes recorded by 14 of the 33 stations were used to evaluate the average horizontal to vertical spectral ratio (HVSR) for each site and the standard horizontal spectral ratio (SSR) between a site and a reference station. The obtained results have been compared to the geological and geophysical information in order to explain the resonance frequencies and the amplification levels with respect to surface geology of the valley. The results indicate that there is no uniform pattern of amplification, because of the complex geologic setting, as the thickness and degree of cementation of the deposits is highly variable.

In the last decades, geophysicists and seismologists have focused their attention on the inversion of empirical surface-waves’ dispersion curves from microtremor measurements for estimating the S-wave velocity structure at a site. This procedure allows a fast and convenient investigation without strong active sources, which are difficult to deploy especially in urban areas. In this study we report on a 2D seismic noise array experiment carried out at Bevagna (central Italy) near the station BVG of the Italian Accelerometric Network (RAN). The site was investigated within the DPC-INGV S4 Project (2007-2009). The Rayleigh- and Love-waves dispersion characteristics were estimated using different methods. The inversion of the dispersion curves was then performed independently, obtaining two estimations for the S-wave velocity profiles. The results of cross-hole logging near the seismic station are used for a comparison. The shear-wave velocity profiles estimated by microtremor analyses range up to 150 m depth. The two independent procedures provide consistent shear-wave velocity profiles for the shallow part of the model (20–30 m in depth) in agreement with the results of the cross-hole logging. Some problems arise between 30–40 m in depth in the profile estimated by surface waves. In this range cross-hole logging evidences an inversion of the S-wave velocity. Although the cross-hole logging stops at 40 m of depth, we are confident about the results provided by the Rayleigh-wave analysis below 40–50 m. This case study suggests that greater efforts should be devoted to exploit the potential of a coupled analysis of Rayleigh and Love waves from microtremor array measurements.