Seismic site-response characterization of high-velocity sites using advanced geophysical techniques: application to the NAGRA-Net

0476623 - GFÚ 2018 RIV GB eng J - Journal Article
Poggi, V. - Burjánek, Jan - Michel, C. - Fäh, D.
Seismic site-response characterization of high-velocity sites using advanced geophysical techniques: application to the NAGRA-Net.
Geophysical Journal International. Roč. 210, č. 2 (2017), s. 645-659. ISSN 0956-540X. E-ISSN 1365-246X
Institutional support: RVO:67985530
Keywords : joint inversion * earthquake ground motions * seismic noise * site effects
OECD category: Volcanology
Impact factor: 2.528, year: 2017

The Swiss Seismological Service (SED) has recently finalised the installation of ten new seismological broadband stations in northern Switzerland. The project was led in cooperation with the National Cooperative for the Disposal of Radioactive Waste (Nagra) and Swissnuclear to monitor micro seismicity at potential locations of nuclear-waste repositories. To further improve the quality and usability of the seismic recordings, an extensive characterization of the sites surrounding the installation area was performed following a standardised investigation protocol. State-of-the-art geophysical techniques have been used, including advanced active and passive seismic methods. The results of all analyses converged to the definition of a set of best-representative 1-D velocity profiles for each site, which are the input for the computation of engineering soil proxies (traveltime averaged velocity and quarter-wavelength parameters) and numerical amplification models. Computed site response is then validated through comparison with empirical site amplification, which is currently available for any station connected to the Swiss seismic networks. With the goal of a high-sensitivity network, most of the NAGRA stations have been installed on stiff-soil sites of rather high seismic velocity. Seismic characterization of such sites has always been considered challenging, due to lack of relevant velocity contrast and the large wavelengths required to investigate the frequency range of engineering interest. We describe how ambient vibration techniques can successfully be applied in these particular conditions, providing practical recommendations for best practice in seismic site characterization of high-velocity sites.
Permanent Link: http://hdl.handle.net/11104/0273093