14:30 〜 14:45
[S07-9-05] Site-specific investigations in the ongoing renewal project of the Swiss strong motion network (SSMNet)
In 2009, the Swiss Seismological Service started a project to renew and expand its strong motion network. A total of 100 new stations are planned to be installed until 2019. The goals of the enlargement of the network are a better coverage of regions with increased seismic hazard and risk, a better knowledge of the variability of ground motion and site effects in Switzerland, the study of secondary phenomena such as landslides and liquefaction and finally the verification and improvement of seismic hazard models.
All new stations are free-field and mainly installed in densely populated areas of high seismic risk, but also in more rural areas with relevant historical seismicity.
Installing the new stations is a step-wise process. After the identification of suitable target areas, a first idea of the local site effects is obtained from H/V surveys and geological information. Important infrastructures, such as hospitals, schools or fire departments, where free-field stations could be built, are identified. At these places, test stations assess the local noise level for several days.
Taking all available information into account, the final station locations are decided. After the station construction, passive and active seismic measurements are performed to characterize the site response. Passive seismic array measurements yield Love and Rayleigh wave dispersion curves as well as the Rayleigh wave ellipticity. Where it seems necessary, active measurements with MASW and body-wave refraction are carried out. CPT measurements aim at assessing the potential for nonlinear soil effects and liquefaction.
The inversion of the surface wave properties supplies shear-wave velocity profiles for the soil structure under the strong-motion station. Based on these, the theoretical amplification can be calculated and compared to the observed empirical amplification. In this way, site-specific phenomena such as edge-generated surface waves or resonance can also be identified.
All new stations are free-field and mainly installed in densely populated areas of high seismic risk, but also in more rural areas with relevant historical seismicity.
Installing the new stations is a step-wise process. After the identification of suitable target areas, a first idea of the local site effects is obtained from H/V surveys and geological information. Important infrastructures, such as hospitals, schools or fire departments, where free-field stations could be built, are identified. At these places, test stations assess the local noise level for several days.
Taking all available information into account, the final station locations are decided. After the station construction, passive and active seismic measurements are performed to characterize the site response. Passive seismic array measurements yield Love and Rayleigh wave dispersion curves as well as the Rayleigh wave ellipticity. Where it seems necessary, active measurements with MASW and body-wave refraction are carried out. CPT measurements aim at assessing the potential for nonlinear soil effects and liquefaction.
The inversion of the surface wave properties supplies shear-wave velocity profiles for the soil structure under the strong-motion station. Based on these, the theoretical amplification can be calculated and compared to the observed empirical amplification. In this way, site-specific phenomena such as edge-generated surface waves or resonance can also be identified.