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The Deep Bedrock in Rome, Italy: A New Constraint Based on Passive Seismic Data Analysis

TitoloThe Deep Bedrock in Rome, Italy: A New Constraint Based on Passive Seismic Data Analysis
Tipo di pubblicazioneArticolo su Rivista peer-reviewed
Anno di Pubblicazione2019
AutoriMarcucci, S., Milana G., Hailemikael S., Carlucci G., Cara F., Di Giulio G., and Vassallo M.
RivistaPure and Applied Geophysics
Volume176
Paginazione2395-2410
ISSN00334553
Parole chiaveAcoustic wave velocity, Ambient vibrations, Deep velocity structures, Dispersion (waves), Dispersion curves, Earthquake effects, High-energy components, Horizontal-to-vertical spectral ratios, Joint inversion, Lime, Low-frequency resonance, Natural frequencies, Shear flow, Shear wave velocity structure, Shear waves, Soils, Surface waves, Vibration analysis, wave propagation
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. © 2019, Springer Nature Switzerland AG.

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cited By 2

URLhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85065162190&doi=10.1007%2fs00024-019-02130-6&partnerID=40&md5=0b2af5cec45568455df940e8024bdbf7
DOI10.1007/s00024-019-02130-6
Citation KeyMarcucci20192395