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Earthquake Hazard and Risk Assessment

The Engineering Seismology group develops the basic tools and techniques used for seismic hazard and risk assessment. These include catalogues of historical and instrumental earthquakes, reliable ground motion mitigation models, high-definition underground models for numerical simulation of earthquakes and the interpretation of historical observations and earthquake recordings at seismic stations. Engineering seismologists produce local seismic hazard maps (microzonation) and link the results to data on building vulnerability so that dependable risk assessments can be carried out.

To develop these tools and techniques, the Earthquake Hazard and Risk Assessment section is divided into four research groups that focus on specific domains, but often also study shared topics of interest. The section is headed by Professor Donat Fäh.

The Strong Ground Motion Seismology and Site Effects research group develops new tools and techniques for improving seismic hazard analysis in Switzerland. Part of its work involves upgrading and expanding the strong motion network through to 2019. Geophysical and geotechnical measurements are taken to determine the properties of the local geological underground at each station, enabling us to interpret any features captured on earthquake recordings. To this end, we have developed special measurement procedures, some of which are based on analysing seismic noise.

The Numerical Earthquake Ground Motion Modelling research group works on methods for numerically simulating the impact of earthquakes. Earthquakes are modelled when there are no instrumental recordings, i.e. particularly for large, damaging earthquakes and sites close to seismic sources. One way of doing this is to calibrate site-specific ground motion attenuation models. Another is to use deterministic modelling of the rupture process and of wave propagation for scenario earthquakes. However, local geological properties must always be properly factored in. The recordings at seismic stations are used to calibrate the numerical models.

Earthquakes are not the only events that cause damage to buildings and infrastructure: secondary earthquake-induced phenomena can wreak havoc as well, for example through soil liquefaction, landslides and tsunamis on lakes triggered by underwater landslides. This is the focal point of the  Earthquake-Induced Phenomena research group. One aim of our earthquake research is to characterise such phenomena with a view to seismic hazard analysis and the recognition of early indications of mass wasting (ground movements) based on giveaway seismic signals. Other phenomena to watch for are short-term foreshocks prompted by processes in the earth's crust, which can produce characteristic electromagnetic and geochemical signals.

The Historical Seismology and Palaeoseismology research group analyses earthquakes predating the establishment of the modern seismic network in the mid-1970s. Data on earlier earthquakes provide important information for anticipatory mitigation measures and enable us to pinpoint where events occurred and estimate their magnitude. Damaging powerful earthquakes are relatively rare in Switzerland, so no instrumental data on them are available yet. Consequently, we have to draw on chronicles from the past, analyse this information using historical methods, and use palaeoseismological methods to interpret geological traces of major earthquakes.