Swiss unprepared for major earthquakes

Red alert for canton Valais (bottom of map) and Basel (top) Keystone

Experts say that earthquakes pose a greater risk to the city of Basel and canton Valais than previously estimated.

The Swiss Seismological Service warns that only a fraction of buildings in the country could survive a major tremor.

The service released a new seismic hazard map on Monday, which increases the risk for Basel, the city destroyed by a major earthquake in the 14th century, and has placed the entire canton of Valais in the highest risk category.

The entire alpine region is in the middle risk category.

The map allows experts to make a more precise estimate of seismic activity over the next 500 years.

The head of the service, Domenico Giardini, says that Switzerland should expect to be hit by earthquakes up to a magnitude of 7.5 on the Richter scale, which could cause billions of francs in damage.

More than 10,000 earthquakes have been measured in Switzerland over the past 800 years, and there have been six registering more than six on the Richter scale in the past 150 years – all in Valais.

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.

New building codes

Giardini said the latest data was the basis for new building codes introduced last year.

Only public buildings belonging to the federal government have to comply to the higher standards.

Giardini is demanding that the safety codes be introduced by the cantons and applied to privately-owned structures as well.

He says adapting the new norm would only lead to a one per cent increase in construction costs.

The findings of the service are also of importance for Switzerland’s nuclear power plants, insurers and the country’s civil protection service.

However, the association representing the nuclear power industry responded to the report by saying its plants were built to withstand far greater tremors than predicted by the map.

swissinfo with agencies

Key facts

Basel was destroyed by an earthquake measuring 6.5 on the Richter scale in 1356.
Around 10,000 earthquakes have been registered in Switzerland over the past 800 years.
The new seismic hazard map presents the risk danger for the next 500 years.
It replaces a map from 1978.