More than 500 earthquakes, mostly moderate in magnitude, are recorded in Switzerland every year, according to a study by the Federal Institute of Technology in Zurich (ETHZ).
“But a strong or even catastrophic earthquake could also occur anytime, anywhere in Switzerland. Earthquakes represent a serious hazard for Switzerland,” the Swiss Seismological Service (SED) at ETHZ said on Tuesday in a statement.
The most recent moderate seismic occurrence was three years ago – a 4.2 earthquake on the Richter scale – which originated 30km below the earth’s surface near the city of Zug in central Switzerland. The event was felt by tens of thousands of people across central and eastern Switzerland.
Moderate earthquakes occur repeatedly in Switzerland, say the SED researchers.
The SED, which monitors earthquake activity and predicts the levels of seismic hazard, released an updated seismic hazard model on Tuesday. The new model replaces an older one from 2004 and is based on improved predictive models, new and more exact data and revised estimates based on historical sources, the ETHZ said.
Overall, estimates of the hazard level in different regions have changed only slightly since 2004, the SED said.
Most risky areas
Canton Valais remains the area with the highest level of hazard, followed by Basel, Graubünden, the St Gallen Rhine Valley and central Switzerland.
According to the SED, only Graubünden, and in particular the Engadine region, has a higher level of hazard than previously assumed. This is explained by a revised understanding of previous earthquakes in the region.
The risk of earthquakes in Switzerland is classified as moderate to average – less likely to occur than in high-risk areas such as Turkey, for example. However, given the density of the population and property in risk areas such as the Basel region, a severe earthquake is the kind of natural disaster with the greatest potential for destruction in Switzerland.
The most recent major earthquake to hit Switzerland was in Basel in 1356. Today, a similar event would cause about CHF80 billion ($83 billion) in damages, the Federal Office for Civil Protection estimated.
Tidal wave fear
Situated at the heart of Europe, Switzerland lies on the edge of the Eurasian tectonic plate. The border of this plate – and hence the area of friction with the neighbouring African plate – follows the line of the Alps.
Basel, on the other hand, sits squarely in the centre of the so-called “Rhine rift valley”, a fault in the Earth’s crust which opened up 30 million years ago when the Eurasian continent fractured along a line running from the North Sea to Switzerland.
Experts fear that an earthquake could also trigger tidal waves caused by landslides into the country’s lakes and reservoirs.
swissinfo.ch and agencies