Publication Date:
2020-02-24
Description:
Abstract In this study, we describe two experiments of
seismic noise measurements carried out in Naples, Italy.
The site allowed measurements to be obtained both at
the surface and in a tunnel that is 120-m-deep. The main
goal was to compare the seismic response evaluated at
the surface to the in-tunnel response, through spectral,
polarization, and resonance directivity analyses. In the 1
to 20 Hz frequency band, the noise level was up to
15 dB higher at the surface than in the tunnel. The
polarization properties and horizontal-to-vertical spectral
ratios appear not to be influenced by the tunnel
geometry or by the topography. Some preferential alignments
were observed in the polarization azimuths computed
at the surface, which are likely to be due to local
sources, rather than morphological features. The absence
of directivity effects and the low noise levels in
the tunnel make this site suitable for installing seismic
stations. We also studied how the subsoil structure affects
the seismic motion at the surface. The dispersive
properties of the Rayleigh waves were investigated
using the spatial autocorrelation method. A joint inversion
of the dispersion data and the horizontal-to-vertical
spectral ratios provided the subsurface Vs profile. The
derived model has a low velocity contrast at depth, such as to generate moderate and broad H/V spectral ratio
peak amplitude. The normalized spectral ratio appears
more appropriate to identify the soil-resonance
frequencies.
Description:
Published
Description:
385 - 400
Description:
4T. Fisica dei terremoti e scenari cosismici
Description:
JCR Journal
Description:
restricted
Keywords:
seismic noise
;
04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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