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Damaging earthquakes are rare in Switzerland, however they pose the greatest damage potential of all natural hazards. With the help of preventive and preparatory measures, potential earthquake damage can be reduced efficiently and the return to normality made easier. Various actors are responsible for protection against earthquakes. As one of these actors, the federal authorities have been coordinating their activities in the area of earthquake mitigation in the context of a programme of measures since 2001.
Compared with other countries in Europe, Switzerland's level of seismic hazard is moderate. Strong earthquakes up to a magnitude of 7 are possible, however they are significantly more rare in Switzerland than in areas of high seismicity like Italy and Turkey. Earthquakes can occur all over Switzerland and there is no area where the seismic hazard may be ignored.
On average, around 500 to 800 earthquakes are registered every year in Switzerland. However, only 25 to 40 of these tremors (5%) with magnitudes of around 3 are perceptible to humans. Considered over a period of 50 years, the probability of occurrence of a magnitude 5.5 earthquake causing local damage is 80%, the probability of a magnitude 6 earthquake causing damage on a regional scale is around 40% and the probability of a magnitude 7 earthquake causing supraregional damage 7 is around 5%. Twelve documented earthquakes causing major damage have occurred in Switzerland since the 13th century. Historical examples include the series of earthquakes in the Canton of Obwalden in 1964 (magnitude 5.3), the Siders earthquake in 1946 (magnitude 5.8) and the Basel earthquake in 1356 (magnitude 6.6). The canton of Valais, the Basel region, the Rhine valley, the Bernese Oberland, the Engadin and parts of the central Switzerland have an elevated earthquake risk compared to other regions. However, earthquakes can occur all over Switzerland.
The level of seismic safety in 85-90 percent of existing buildings and facilities in Switzerland is currently unknown or insufficient. The relatively high vulnerability of existing buildings means that considerable damage may be expected in the event of an earthquake. Due to the high density of development, the earthquake risk is mainly concentrated in urban centres. The risk is particularly high when these are located on poor geological terrain in which earth tremors are most strongly amplified.
Earthquake risk mitigation in Switzerland started in the mid-1990s. Since then, several important steps have been taken towards a more systematic implementation of preventive measures, particularly in relation to building codes, technical guidelines and the systematic integration of seismic safety into public building projects. Although some progress has been achieved since the publication of the latest generation of building codes in 2003, much remains to be done in the private sector to achieve the consistent integration of seismic safety into building projects. The 26 cantonal building authorities, which enjoy a high degree of autonomy, and the building professionals, who are generally solely responsible for the compliance of projects with building codes, have a very important role to play in this regard.
In this context, the federal authorities are responsible for earthquake monitoring and national hazard assessment (Swiss Seismological Service). The federal authorities implement or prescribe preventive measures within their area of competence, that is for buildings and infrastructure systems that are property of the Confederation or require federal approval and federal financing. In all other areas, the cantons, communes and, above all, private individuals and institutions are responsible for the implementation of preventive measures. The building legislation is the responsibility of the cantons and, hence also, the formulation of earthquake-specific requirements. The cantons are also responsible for post-earthquake management with the support of the federal authorities. Insurance companies in Switzerland are not obliged to cover earthquake damage. Property owners must decide themselves whether they would like to be insured against earthquake damage.
Further information is available in German and French.
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