Sub-surface characterization of the Anphiteatrum Flavium Area (Rome, Italy) through single-station ambient vibration measurements

The Amphiteatrum Flavium in Rome (Italy) is one of the most known monument in the world. With the aim of understanding the seismic response of the area where the Amphiteatrum Flavium is built and in- vestigating possible soil-structure interactions, we performed a seismic experiment in 2014, based on ambient vibration (AMV) recordings. The measurements were performed at the original ground level, on the foundation and at different oors of the monument. Data were analyzed in terms of standard Fourier analysis (FAS) and horizon- tal-to-vertical spectral ratio technique (H/V). Moreover, we performed an active P-wave seismic tomography analysis of the foundation ma- terials to better understand their in uence on the recorded signals. Our results point out that there is a strong temporal and spatial sta- bility of the H/V curves, suggesting a uniform seismic response at the monument site. Conversely, spectral amplitudes of AMV show rele- vant temporal and spatial variability at the investigated site, due to the daily variations of AMV levels and to the low-pass ltering effect of the stiff Amphiteatrum Flavium foundation that strongly attenu- ates the signals for frequencies above 4 Hz, i.e. those mostly originated by traf c vibrations. Moreover, we observe that the main vibration frequencies of the super-structure are not present as energetic peaks in the spectra of the ground-motion recorded at its base.