Site effect estimation through site characterization from ambient noise recordings,

Montpellier, France

European
Seismological
Commission

Site effect assessment is an important step in seismic risk mitigation. There is therefore a drastic need for co
proxies to site effects estimates. In that context, a new promising approach was proposed, using the time-avera
over the top z meters with z varying form 5, 10, 20 and 30 meters (Vsz) and the fundamental resonance frequen
two-parameters characterization of a site. Then to assess site effect, a Site Amplification Prediction Equat
completely defined by these two parameters was build-up based on Japanese data from the KiK-Net network. Thu
to be validated using other dataset. For that aim the EUROSEIS-test data is a suitable one. The EUROSE
sedimentary basin in northern-Greece that has been thoroughly investigated through grants from the European C
mainly to study site effects. Fourteen accelerometric stations have been installed since 1995, that to date recorded
100 events. After a review of the main available information over the EUROSEIS-test, we end up with a poor Vs
for some of the accelerometric stations. Thus eight accelerometric stations were selected for noise array me
surveys to provide more details information about Vsz and f0 parameters. The noise array technique has been pro
decades ago but its development is still in progress, particularly regarding the inversion step. Different approaches
el al. 2009, Renalier et al. 2009) were tested in this study to provide Vsz. These two inversion strategies provide
Vsz for z equals to 10, 20 and 30 meters. With the resulting Vsz and f0 from noise analysis, a validation-test of th
SAPE was realized. The results of such a comparison are encouraging and indicate as well limitations of the SAP
It is a promising tool for engineering and seismic risk management.