Basel has been rocked by another earth tremor, this time measuring 3.1 on the Richter scale, centred on the site of a planned geothermal power plant.
This time buildings stood up to the force unlike the minor damage inflicted by a small earthquake in December that clocked a reading of 3.4. Nobody was hurt in either of the two incidents.
The latest tremor took place at 08.19 on Saturday, prompting around 40 residents to call the emergency services.
Work on the Deep Heat Mining project stopped last month following a series of tremors and will not resume until at least the end of January when experts are expected to conclude their analysis.
The project plans to recover heat to generate electricity by pumping water deep into the Earth's crust.
The injection of water into rocks five kilometres below the surface began at the start of December last year, but only lasted a few days. Since the process started more than 100 small tremors have been recorded.
The canton Basel City prosecutor had already launched an investigation after last month's significant tremor to determine whether the company behind the project, Geopower Basel, broke any laws or should be made to pay for damage.
The canton's president, Barbara Schneider, is due to meet the company together with police representatives on Wednesday in an effort to find a solution to the problem.
Basel is one of the areas in Switzerland particularly prone to seismic activity. In 1356, the city was almost entirely destroyed by a 6.5-magnitude earthquake.
The pilot project to build a geothermal power plant is the first commercial endeavour worldwide to tap heat using the so-called hot fractured rock technique.
Water is injected through boreholes to extract energy from hot dry granite, and when it returns to the surface as steam it is used to generate electricity.
The planned power plant is projected to deliver heat to 2,700 homes and electricity to 10,000.
To shelve the project now would be extremely costly as some SFr56 million ($45 million) of the SFr80 million ($64.7 million) budget has already been spent.
Canton Basel City has stumped up SFr32 million, leading a host of other investors including energy suppliers.
swissinfo with agencies
The Swiss Deep Heat Mining project aims to set up a geothermal power plant in Basel by 2009.
Until now, environmentally-friendly geothermal power has only been generated in areas where heat is close to the surface, such as in volcanic regions.
The Basel plant should be able to produce 20,000 megawatt-hours of electricity per year, and 80,000 megawatt-hours of heating.
The water injected five kilometres down reaches temperatures of around 200 degrees Celsius.
It would be first commercial power plant of it kind anywhere in the world.
In Switzerland, between 300 and 400 earthquakes are recorded annually.
Normally there are three or four earthquakes measuring in the region of 3.4 on the Richter scale every year in Switzerland.
The last tremor to cause any noticeable damage struck canton Graubünden in 1991.
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