Groningen gas earthquake could destroy two of three homes

earthquake Richter. (Picture: Matt Katzenberger/Flickr)

About 152 thousand of the 212,500 houses and apartments in Groningen are not safe if a major earthquake should strike. That is the conclusion of engineering firm Van Rossum's impact analysis commissioned by the province of Groningen, NRC reports. 

In February the steering committee commissioned by Minister Henk Kamp of Economic Affairs estimated that only between 30 thousand and 90 thousand of the houses in Groningen were not earthquake resistant. But the members of the steering committee only looked at ground-built buildings, and did not take apartments and flats into account.

According to Van Rossum, that is exactly where the most risk lies. "High apartment buildings especially do not meet the earthquake loads indicated in the provisional Dutch Practice Guideline." the engineering firm wrote in their report. The guideline was prepared in consultation with specialists from, among others, TNO, TU Delft, NAM and engineering firm ARUP.  They calculated the minimum requirements a building must meet in order not to collapse.

The most vulnerable homes in Groningen are those built before 1920. Van Rossum also estimates that another 20 thousand buildings will have to be strengthened so that they do not collapse in a major earthquake. These buildings include schools, hospitals, monuments and retirement homes.

This, of course, will also increase the estimated cost for making sure that the homes and buildings are safe. In February the steering committee estimated that strengthening the buildings will cost 6.5 billion euros. Van Rossum's estimation is at 30 billion euros.

Exactly how unsafe these houses are, is still unclear and will have to be determined for each property individually. The not-yet-determined risk standards will also play a role. It is clear that this operation will have a major effect on the area and the residents. A number of houses will have to be demolished and rebuilt. Other houses will have to be completely stripped down and fitted with steel structures embedded in concrete floors. The average cost per property is estimated at 186 thousand euros.