GNGTS 2016 - Atti del 35° Convegno Nazionale

366 GNGTS 2016 S essione 2.2 out within and in proximity of the unstable zones, while these peaks are not present in the measurements carried out on the plateau zone. The seismic energy in the frequency higher than 5.0 Hz can be related to the vibrational behavior of the dislodged rock blocks, according to Got et al. (2010) and Galea et al. (2014). In fact, Fig. 2 shows that resonance peaks in HVSR curves are much more evident in areas having higher density of fractures and blocks, as the zone where the three main joints are located. Polarization analysis. Fig. 3 shows some examples of the polarization analysis results, giving information about the particle motion behavior in the different areas. For stations on the stable plateau area (e.g. FA01 showing in Fig. 3), the noise analysis points out that there are neither HVSR peaks nor polarization of the particle motion. Instead, the resonance peaks in the HVSR curves obtained on the unstable zone (e.g. FA07 showing in Fig. 3) show Fig. 3 – Comparison of HVSR curve and polarization analysis results (ellipticity and strike) in the different areas.