BASEL—Efforts to tap energy deep below the earth’s crust to
provide power for homes in the Swiss city of Basel may have to be scrapped after
setting off tremors.
The plan to use geothermal energy to generate electricity for
10,000 homes and heat for 2,700 others is on hold after it caused earth tremors
twice in less than a month, prompting frightened residents to flood emergency
services with calls.
"We had expected the experiment to cause minor tremors. But
so far we do not know in detail why the quakes were bigger than expected," said
Stefan Wiemer of the Swiss Seismological Service.
In the Swiss model, geothermal energy is generated through
high-pressure injection of water into hot granite at a depth of 5,000 meters.
This produces steam used to drive turbines.
A firm working on the $67 million project has handed a report
to the city government and is waiting for a decision on its future.
A first quake in early December lasted 20 seconds and
registered 3.4 on the Richter scale. Water pumped into the depths set off a
second, slightly weaker quake on Saturday.
Basel, a seismic region, was almost completely destroyed by
an earthquake in 1356. Small tremors, often barely perceptible, are common.
Experts say the deeper water is pumped below the earth’s surface the harder
it is to predict whether it will set off stronger tremors.
