Geothermal plant likely cause of earthquakes

In mid-August 2009, a quake damaged a number of homes in the area. One month later, six other measurable tremors were recorded.

According to regional broadcaster SWR, the strongest quake registered at 2.5 on the Richter scale.

In November some 40 residents reported cracks in their walls following the quakes, the station said.

Experts commissioned by the state found that since the plant began operating in November 2007, the number of measurable micro-earthquakes had increased.

The report recommended increased observation of the ground around the facility to enable quicker reaction by authorities in the case of more tremors.

The earthquakes were probably caused by a rise in pore water pressure – the pressure created by groundwater held in rock or soil underground – resulting from the plant’s operations.

The power plant pulls hot water up from rock more than three kilometres below the ground surface, converting it to electricity and heat. The water is then returned to the earth through a second boring.

The Landau geothermal power plant, operated by Geox, is the largest of its kind in Germany.

Following the quakes, the state Economy Ministry increased safety requirements for the plant, enforcing a lower output and a reduction of pressure for the water being reintroduced into the earth, SWR reported.

The subsidiary of energy provider Pfalzwerke and EnergieSüdwest was also required to take out liability insurance covering up to €50 million in damages per year.

DPA/The Local/ka