Publication Date:
2020-12-14
Description:
In the framework of the EU-NERIES project, 20 sites among all European strong
motion sites in Italy, Greece, T urkey and France were selected to be representative of
most common soil classes, and for which shear-wave velocities from borehole
measurements (cross-hole and down-hole tests) are available. Passive (array noise) and
active experiments have been carried out at these sites in order to evaluate the ability
of surface waves technique to provide reliable estimates of shear-wave velocity profiles.
In order to stay cheap and feasible, active seismic experiments involving 24 geophones
and hammer source were carried out at all sites. Data were processed by using the
MASW technique and Rayleigh and Love waves dispersion curves were retrieved from
5-10 Hz to 30-50 Hz. Passive array experiments were also performed by using 8
seismological stations linked with wireless connections and monitored with near
real-time processing. Combining up to four different arrays with aperture ranging from
10 m and to 900 m, Rayleigh and Love waves dispersion curves were derived over a
broad frequency range (from 0.5 Hz up to 45 Hz) by using the FK and MSPAC
techniques. At about 75% sites, dispersion curves from ambient vibration and MASW
are in good agreement over the overlapping frequency band. T he other 25% sites
correspond to complex geometrical site structures. Whatever the site, passive
experiments are shown to be very suitable to retrieve accurate estimates of phase
velocities at high frequency (over 20-30 Hz). T his experiment also clearly outlined the
limited penetration depth (comprised between 15 and 25 m) of the MASW technique.
Inversion of dispersion curves to derive shear-wave profiles and EC8 site class (which is
mainly based on Vs30) is a difficult and highly debated issue. Here we test an alternative
to get average shear-wave profiles and especially Vs30 from the dispersion curves only.
For these 20 sites, we show that site classes may be estimated directly from the
dispersion curves. T heses results are confirmed by an extensive study involving about
800 velocity profiles from real sites.
Description:
Published
Description:
Montpellier, France
Description:
4.1. Metodologie sismologiche per l'ingegneria sismica
Description:
open
Keywords:
Vs30, dispersion curve
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
Poster session
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