Seminar – Donat Fäh

The Swiss Seismic Hazard Model: Background and National Implementation

Prof. Donat Fäh (ETH Zürich)

Over the past few decades, the national seismic hazard maps for Switzerland have been revised twice. This was coordinated and harmonised with the seismic hazard analysis for nuclear power plant sites in Switzerland (the Pegasos and Pegasos Refinement projects), which were carried out in a SSHAC process. To this end, the underlying data sets were completely revised (historical and instrumental earthquake catalogues and source zoning data) and a stochastic ground motion model for Switzerland was developed. A key milestone was the development of a reference rock profile for the seismic hazard maps, which is needed when the hazard maps are used for site-specific seismic hazard assessment and microzonation with a site response layer. The national seismic hazard maps formed the basis for revising the Swiss building code (SIA 261) with regard to determining five seismic zones, defining the soil classes, shaping the elastic response spectra and establishing aggravation factors for the three importance-classes of buildings. Additionally, provisions for site-specific seismic hazard analysis and microzonation were established in a new standard (SIA 261/1, 2020). All developments are currently also being used to implement the revised Eurocodes (EC8) in Switzerland.