000009532 001__ 9532
000009532 005__ 20141205150215.0
000009532 04107 $$aeng
000009532 046__ $$k2008-10-12
000009532 100__ $$aBertrand, Etienne
000009532 24500 $$aSeismological Measurements for Site Effect Investigation in the Var valley, Nice, France

000009532 24630 $$n14.$$pProceedings of the 14th World Conference on Earthquake Engineering
000009532 260__ $$b
000009532 506__ $$arestricted
000009532 520__ $$2eng$$aQuantitative assessment of site effects, is a major issue in seismic hazard and engineering seismology studies. The frequency dependent site amplifications, observed since decades during the past earthquakes over the world, are known to be mainly caused by reverberations and resonance effects of S-waves within unconsolidated sediments overlaying stiffer formations. We carried out several seismological investigations of site effects in the Var Valley near the city of Nice, southeastern France. The valley is less than 1 km width but previous geophysical and geotechnical studies show that the bedrock could be reached at a maximum of about 200 m depth. In the studied area, the sediments are mainly composed of sand and gravel layers overlaying Pliocene marl. In order to investigate the effect of this sedimentary filling, two kinds of field experiment were set up through the sedimentary basin during 2005 and 2006. Firstly, several profile of ambient vibration recordings were done through the valley in order to apply the Nakamura's technique and estimate the resonance frequency of the soil column beneath the recording points. We also used array technique in order to estimate the Rayleigh waves dispersion characteristics from ambient vibrations recordings. The inversion of the observed dispersion curves allows us to recover the shear wave velocity profiles of the subsurface. The H/V ratios exhibit amplifications down to 0.5 Hz in the centre of the valley and the shear wave velocity in the sediments is estimated close to 300 m/s. These results are in good agreement with geotechnical observations and 1D linear-equivalent modelling. Secondly, a temporary array of 10 broadband velocimeters was deployed in order to record the surrounding seismicity. These data help us defining transfer functions by the computation of spectral ratio between the recordings at a reference station located on rock site and the ones obtained with the station located in the basin. Resonance frequency in the valley is observed between 1 Hz and 4.1 Hz.

000009532 540__ $$aText je chráněný podle autorského zákona č. 121/2000 Sb.
000009532 653__ $$aseismic hazard, site effect, H/V, site/reference, spectral ratio

000009532 7112_ $$a14th World Conference on Earthquake Engineering$$cBejing (CN)$$d2008-10-12 / 2008-10-17$$gWCEE15
000009532 720__ $$aBertrand, Etienne$$iDupuis, Jérémy$$iDuval, Anne-Marie$$iVidal, Sylvain
000009532 8560_ $$ffischerc@itam.cas.cz
000009532 8564_ $$s37693792$$uhttps://invenio.itam.cas.cz/record/9532/files/12-01-0080.pdf$$yOriginal version of the author's contribution as presented on CD, Paper ID: 12-01-0080.
000009532 962__ $$r9324
000009532 980__ $$aPAPER