(Here is the text of the article, translated by Deepl. The content is coherent and more or less what we often experience in the engineering office and what many people play down or forget. Only houses are mentioned here, but it also concerns infrastructure such as bridges, roads, slope constructions, dams, underground pipes (gas, water, sewage, etc.).
__Four out of five residential buildings in Switzerland were built before the modern building standards for earthquake safety. Their safety is unclear. An additional risk factor is soil reinforcement, which affects large settlement areas in Switzerland.__.
Over 300’000 buildings collapsed in the severe earthquake in southern Turkey and Syria. Around 60,000 people died, most of them in the rubble of their homes. It was the most devastating earthquake in Turkey in over 1000 years.
The earthquake catastrophe has also alarmed Swiss homeowners: there have been an increasing number of enquiries about how houses can be checked for earthquake safety, says Pia Hannewald, President of the Society for Earthquake Engineering (SGEB).
“In some cases, building owners are not yet aware that they are responsible for the safety of their building stock and thus also for earthquake safety,” says Hannewald. Exceptions are the Valais or the Basel area, which are considered earthquake risk areas.
Overall, the risk of severe earthquakes in Switzerland is not as high as in Turkey. But “damaging earthquakes” can occur in this country every 100 years or so, according to the earthquake service SED.
__Risk factor: Building on soft ground__
The last earthquake of this class occurred in Sierre in 1946. It caused millions of dollars worth of building damage and four people died. Today, a comparable quake of magnitude 5.8 would cause much more damage, because Switzerland is much more densely populated. In addition, the settlement area has expanded onto soils that amplify earthquake waves.
For five years, Paolo Bergamo at the Swiss Seismological Service (SED) has been evaluating small and very small quakes over the past 20 years. In the process, he has investigated how the quakes affect different soil structures. The finding: on soft soils, an earthquake can amplify up to tenfold. This affects areas along rivers or lakeshores, where many residential areas were built in the post-war years.
__Building standards: introduced late__
In addition, hardly any attention was paid to earthquake resistance when building houses in the past. The first standards were introduced in 1989, but some of them were not very well observed. It was not until 2003 that modern standards (SIA 261) were introduced to prevent a building from collapsing in the event of a moderate earthquake. According to Blaise Duvernay, head of earthquake prevention at the Federal Office for the Environment (FOEN), what was built before that – over 80 per cent of residential buildings – is “a big unknown”.
If a strong earthquake like the one that hit Basel in 1356 were to occur today, the consequences would be fatal: “Collapses, deaths, seriously injured people, a large number of homeless people would also be seen in Switzerland,” says Duvernay. Despite this danger, there is no reliance on government regulations or controls, as is common in fire protection. The responsibility lies with the individual building owners. It is up to them to check their buildings for earthquake resistance and, if necessary, to reinforce them accordingly.
__Principle of personal responsibility__
Corresponding standards for this have been in place since 2017 (SIA 269/8): They stipulate that the earthquake safety of old buildings does not necessarily have to correspond to that of a new building. However, a check and retrofitting is recommended for major renovation work. There are still only a few cantons that explicitly refer to this in their building regulations. This does not change the responsibility of the owners.
Since last year, when we had that earthquake that everyone could actually feel here in Basel, I’ve been wondering what would happen if a stronger one was to come. It was surreal to hear our walls roar for a couple of seconds.
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(Here is the text of the article, translated by Deepl. The content is coherent and more or less what we often experience in the engineering office and what many people play down or forget. Only houses are mentioned here, but it also concerns infrastructure such as bridges, roads, slope constructions, dams, underground pipes (gas, water, sewage, etc.).
__Four out of five residential buildings in Switzerland were built before the modern building standards for earthquake safety. Their safety is unclear. An additional risk factor is soil reinforcement, which affects large settlement areas in Switzerland.__.
Over 300’000 buildings collapsed in the severe earthquake in southern Turkey and Syria. Around 60,000 people died, most of them in the rubble of their homes. It was the most devastating earthquake in Turkey in over 1000 years.
The earthquake catastrophe has also alarmed Swiss homeowners: there have been an increasing number of enquiries about how houses can be checked for earthquake safety, says Pia Hannewald, President of the Society for Earthquake Engineering (SGEB).
“In some cases, building owners are not yet aware that they are responsible for the safety of their building stock and thus also for earthquake safety,” says Hannewald. Exceptions are the Valais or the Basel area, which are considered earthquake risk areas.
Overall, the risk of severe earthquakes in Switzerland is not as high as in Turkey. But “damaging earthquakes” can occur in this country every 100 years or so, according to the earthquake service SED.
__Risk factor: Building on soft ground__
The last earthquake of this class occurred in Sierre in 1946. It caused millions of dollars worth of building damage and four people died. Today, a comparable quake of magnitude 5.8 would cause much more damage, because Switzerland is much more densely populated. In addition, the settlement area has expanded onto soils that amplify earthquake waves.
For five years, Paolo Bergamo at the Swiss Seismological Service (SED) has been evaluating small and very small quakes over the past 20 years. In the process, he has investigated how the quakes affect different soil structures. The finding: on soft soils, an earthquake can amplify up to tenfold. This affects areas along rivers or lakeshores, where many residential areas were built in the post-war years.
__Building standards: introduced late__
In addition, hardly any attention was paid to earthquake resistance when building houses in the past. The first standards were introduced in 1989, but some of them were not very well observed. It was not until 2003 that modern standards (SIA 261) were introduced to prevent a building from collapsing in the event of a moderate earthquake. According to Blaise Duvernay, head of earthquake prevention at the Federal Office for the Environment (FOEN), what was built before that – over 80 per cent of residential buildings – is “a big unknown”.
If a strong earthquake like the one that hit Basel in 1356 were to occur today, the consequences would be fatal: “Collapses, deaths, seriously injured people, a large number of homeless people would also be seen in Switzerland,” says Duvernay. Despite this danger, there is no reliance on government regulations or controls, as is common in fire protection. The responsibility lies with the individual building owners. It is up to them to check their buildings for earthquake resistance and, if necessary, to reinforce them accordingly.
__Principle of personal responsibility__
Corresponding standards for this have been in place since 2017 (SIA 269/8): They stipulate that the earthquake safety of old buildings does not necessarily have to correspond to that of a new building. However, a check and retrofitting is recommended for major renovation work. There are still only a few cantons that explicitly refer to this in their building regulations. This does not change the responsibility of the owners.
Since last year, when we had that earthquake that everyone could actually feel here in Basel, I’ve been wondering what would happen if a stronger one was to come. It was surreal to hear our walls roar for a couple of seconds.