Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/12361
Authors: Marcucci, Sandro* 
Milana, Giuliano* 
Hailemikael, Salomon* 
Carlucci, Giorgia* 
Cara, Fabrizio* 
Di Giulio, Giuseppe* 
Vassallo, Maurizio* 
Title: The Deep Bedrock in Rome, Italy: A New Constraint Based on Passive Seismic Data Analysis
Issue Date: 19-Feb-2019
DOI: 10.1007/s00024-019-02130-6
URI: http://hdl.handle.net/2122/12361
Keywords: Ambient vibrations
horizontal-to-vertical spectral ratio
surface-waves dispersion curve
joint inversion
Subject Classification04.06. Seismology 
Abstract: Seismic resonance inside sedimentary basins severely influences ground shaking at the free surface in case of earthquakes. Starting from few observations of a low-frequency resonance in the historical center of Rome, Italy, we performed several single-station ambient vibration measures to verify and estimate the resonance frequency in a wide area of the city by Horizontal-to-Vertical spectral ratio method. We verified a stable low-frequency peak in the range 0.3–0.4 Hz. Recordings of August 24th 2016, Mw 6.0 Amatrice earthquake, available both inside and outside the basin of Rome, confirm the presence of high-energy components at frequencies of 0.2–0.4 Hz within the basin. These observations support the hypothesis of a deep seismic impedance contrast responsible for the low frequency resonance. To infer the depth range of subsoil deposits related to this impedance contrast, we analyzed ambient vibration data recorded by 2-D seismic arrays aiming at retrieving the shear-wave velocity structure up to relevant depths. To increase the investigation depth (up to 2000 m), we jointly inverted for Rayleigh-waves dispersion and ellipticity curves and resonance frequency. The shear-wave velocity profile shows two main discontinuities at depths of about 500 m and 1800 m that can be related to the bottom of the Plio-Pleistocene filling of the Rome basin and to the top of the basal limestone formation, respectively. These results fill a gap of knowledge about the deep velocity structure in the city that may be helpful for ground-motion scenario studies.
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