GNGTS 2016 - Atti del 35° Convegno Nazionale

28 GNGTS 2016 S essione A matrice Fig. 1 – Geological map of the near-surface geology of Acquasanta Terme town; the red and green triangles represent the seismic stations used in this study. Preliminary results of the spectral ratios on ambient noise (HVNSR) is shown for each seismic station. inconsistencies on the monument. In particular, the TLS high resolution scans allow to perform a detailed geometrical analysis of the structure (e.g. verticality of walls, shifts), whereas the shootings with drone allow to cover the non-visible parts from the ground and unreachable nor inaccessible ones. The geometrical analysis has been combined with thermographic inspection of the external walls (cf. Costanzo et al. , 2015). The Acquasanta Terme town was built on terraces constituted by variable thickness of alluvial deposits resting on a travertine layer. This later is overlapped to the bedrock represented by calcareous-marly formation, named marl with Cerrogna and Bisciaro (see geological map in Fig. 1). Temporary seismic stations were installed along a WNW-ESE profile to investigate the role played by near-surface geology in amplifying the soil shaking. All seismic stations are equipped with three-component 20s velocity transducer and three-component accelerometric transducer. The horizontal components were oriented along the north-south and east-west directions. Data were sampled at 250 Hz using 24-bit analog-to-digital converters, and time synchronism was provided by a GPS system at each station. Furthermore, all stations were equipped with solar panels for power supply and an antenna for wireless data transmission. Such data transmission was based on HyperLAN 5GHz band. All data collected by seismic stations were wireless transmitted and in real time to the server installed in the municipal offices. Using continuous recording, we computed spectral ratios on ambient noise (HVNSR) (Nakamura, 1989). All of the signals were processed with a detrigger algorithm (SESAME, 2004), to remove noise windows containing disturbing and transient phenomena. The single window length has been set to 50 s, to enhance the resolution in the low-frequency range. The Fourier spectra were smoothed with a Konno and Omachi (1998) algorithm, and HVNSR was evaluated on the geometrical mean of the Fourier spectra of the horizontal components.