Earthquakes - new hazard model for Switzerland

Every year, the Swiss Seismological Service (SED) over 500 earthquakes in Switzerland. The last earthquake of medium magnitude occurred a good three years ago: near Zug, an earthquake of magnitude 4.2 occurred 30 km deep in the earth's interior. This was clearly felt by tens of thousands of people in large parts of central and eastern Switzerland. This example makes it clear that moderate earthquakes occur again and again in Switzerland. However, a strong or even catastrophic quake can occur at any time and anywhere in Switzerland. How often and how strong the earth could quake in certain places in the future is one of the research priorities of the Swiss Seismological Service.

Different regions at risk

Estimates show: Earthquakes are the natural hazard with the greatest damage potential in Switzerland. On behalf of the federal government, the SED monitors earthquake activity and estimates the earthquake hazard in Switzerland. At regular intervals, it also publishes a model that describes possible future earthquakes and the associated ground motions. The updated earthquake hazard model now published is based on improved forecast models, new and much more accurate data, and revised estimates from historical sources. It supersedes the 2004 model and allows for a much more robust estimate of hazard.

Experts and representatives of the authorities use the new model as a basis for making decisions in the field of earthquake preparedness and risk management. Overall, the hazard assessment for individual regions has changed only slightly since 2004: Valais remains the area with the highest hazard, followed by Basel, Grisons, the St. Gallen Rhine Valley and Central Switzerland. Only the canton of Graubünden, in particular the Engadin, is more at risk than previously assumed, according to the SED assessment. This slightly higher classification is mainly explained by an adjusted assessment of past quakes.

Different cards - different aspects

In addition to the classic hazard map, which uses acceleration values to map where and how often earthquakes of a certain magnitude are to be expected, the SED is launching two other products this year. They provide the population with easier access to the relevant information:

One of the two new maps illustrates the effects of earthquakes of different magnitudes. The other map shows how often earthquakes of a certain magnitude occur. All products can be explored in an interactive web tool.

Also striking is the new color concept of the hazard map: the "harmless" colors, green and blue, which dominated the 2004 map, have been replaced by yellow, orange, red and violet hues. This new coloring better reflects the actual earthquake hazard in Switzerland: in principle, a strong earthquake is possible at any time in any region of Switzerland.

Take protective measures

An important parameter in the calculation of earthquake hazard is the expected ground acceleration. In recent years, researchers have collected numerous new data in the vicinity of major quakes in Switzerland and abroad. The subsequent evaluations showed that the ground moves more strongly in some quakes than previously assumed. Based on this knowledge, the SED has adjusted the expected ground motions accordingly. These values are particularly important for civil engineers in order to design buildings and infrastructures in an earthquake-compatible manner.

Besides engineers, the hazard map is also an important tool for authorities, insurance companies and researchers. It serves these interest groups primarily as a basis for making decisions in the field of earthquake precautions and integral risk management. In addition, the standards for earthquake-resistant construction are based on the hazard map.

Earthquake hazard online:

• Maps: Discover and compare maps of impacts, hazards, and magnitudes with other parameters and time periods in the Webtool.
• Background: Further information as well as a detailed scientific report on the earthquake hazard model here.
• Professionals find further information as well as specific data and characteristic values here.