Seismology / SED

The SED monitors the seismic activity in Switzerland and close-border regions, and assesses Switzerland’s seismic hazard. In 1878 the Earthquake Commission was established by Switzerland, even before Japan and Italy created similar official bodies. In its present form as an external department of ETH Zurich, the SED exists since 2009 and employs about 60 scientists, technicians, doctoral candidates and administrative staff. A major part of the research activities is financed by third-party funding. The group conducts research in the framework of a wide and varied range of European and international projects in collaboration with other institutions, which ensures a lively professional exchange well beyond national borders. Although the main emphasis is placed on topics relevant for Switzerland, the SED also participates in projects abroad. As an example, currently a network of more than 30 stations in Bhutan, and several stations in Greenland, are being operated by the SED.

Earthquakes in Switzerland

Two earthquakes per day are registered on average in Switzerland and in the adjoining regions, which translates to between 500 and 800 events per year. Of these, approximately 10 are strong enough (magnitude of approx. 2.5 and above) to be felt by the general population. Compared to other European countries, Switzerland exhibits a moderate seismic hazard, though regional differences exist. More earthquakes than in other regions are registered in the Valais, Basel, the St. Gall Rhine Valley, central areas of the Grisons, in Engadine and in Central Switzerland. A strong earthquake with a magnitude of about 6 must be expected on average every 60 to 100 years. The last such event occurred in 1946 near Sierre in the Valais. Such an earthquake, however, can happen again in Switzerland anytime, anywhere.

Earthquake monitoring and warning

Since 1975 the SED monitors seismic activity in Switzerland with a network of stations equipped with real-time telemetry and centralised data acquisition. The broadband network similar to its present configuration exists since the mid-1990s.

The highly sensitive seismometers record even the slightest shaking, and are able to register vibrations along a broad range of frequencies. These special features allow the group to not only monitor earthquakes on a global and regional level, but also to study the evolution of the Earth and the formation of the Alps, to investigate micro-earthquakes, like those occurring during geothermal activities, and to determine geotechnical characteristics of the subsurface.

The data of the more than 150 broadband and strong motion seismometers are transmitted continually and in real time to the central data centre in Zurich. In addition, the SED maintains a pool of mobile stations in collaboration with the Seismology and Geodynamics group under Professor Domenico Giardini for conducting short-term measurement campaigns and field experiments.

An alert system, maintained and constantly being improved by a team of scientists, technicians and programmers, is now capable of detecting earthquakes and determining their location in less than 30 seconds. In case of an earthquake, the SED informs the public, authorities and media concerning the magnitude, location and possible impacts of an earthquake. In addition, the 24/7 SED on-call service provides information about earthquakes to all interested parties.

There is a need for research into how to further improve such alert systems, in particular regarding early warning systems: electromagnetic waves, as they are used in communications, propagate much faster than seismic waves. Based on this fact, it is currently possible to issue a warning to areas at some distance from the epicenter of the earthquake a few seconds before the strongest shaking, provided the earthquake is detected soon enough. The SED pursues research that aims to optimise this type of early warning system, and investigates whether the magnitude of an earthquake can be determined reliably based on the seismogram output transmitted in the first few seconds of an event.