Geothermal power quakes find defenders

Shanta Barley, New Scientist 16 Sep 09;

Geothermal energy is in the dock in Germany, but some scientists are pleading for leniency.

A government panel is investigating claims by the geological survey for the state of Rhineland-Palatinate that a geothermal plant triggered a magnitude-2.7 earthquake on 15 August in the town of Landau in the state. If the panel finds against the company that built the plant, Geo X of Landau, it could be shut down.

Geothermal plants work by pumping water into hot rocks several kilometres down, forcing small cracks in the rock to expand. Steam escapes through the cracks to the surface, where it drives a turbine, producing clean energy. But critics say the process increases the risk of earthquakes.

"Any process that injects pressurised water at depth into rocks will cause them to fracture and possibly trigger earthquakes," says Brian Baptie, an earthquake specialist at the British Geological Society.
Whose fault is it?

Engineers rather than technology must take some of the blame, says Roy Baria, a geophysicist on the panel reviewing the Landau quake, who also works for geothermal energy company EGS Energy, based in Penzance, UK . Past quakes triggered by plants in Basel, Switzerland, were avoidable, he says. "The engineers failed to adhere to best-practice guidelines."

Even the worst geothermal earthquakes have failed to topple a building or kill a human, says Ernest Majer, a seismologist at the Lawrence Berkeley National Laboratory in California, pointing out that geothermal power isn't the only industry that triggers earthquakes.

"Any industry which injects high-pressure fluid into rock, and that includes the oil, nuclear and carbon sequestration projects, has the potential to cause tremors," he says.