A fracking company is calling for the safety limits on earthquakes caused by its activity to be relaxed after it was forced to stop work because of a small tremor for the second time in four days.
Cuadrilla caused what is described as a “microseismic event” measuring 1.1 on the Richter scale at Preston New Road in Lancashire yesterday, the strongest of 27 tremors since it resumed fracking two weeks ago.
Under the government’s “traffic light” system, designed to prevent more serious earthquakes, the company has to cease fracking for 18 hours after a tremor of more than 0.5 on the Richter scale, even though tremors below 1.5 magnitude cannot be felt at the surface. Cuadrilla also had to stop work on Friday after a 0.8 event.
Francis Egan, Cuadrilla’s chief executive, said the limit for a “red” event which requires fracking to stop should be increased to a magnitude of 2. He said: “We appreciate the requirement for a conservative approach and will follow the traffic light system. That said, we consider that a red light limit of circa 2.0ML [local magnitude] would provide more than adequate assurance that no harm or damage could arise from fracking.” He said the limit in the UK was far lower than in other countries, with fracking companies in the US getting a red light at between 2.7 and 4.5, depending on the state.
Mr Egan said the traffic light system had been designed to reassure people but the requirement to measure and report on tiny events was having the opposite effect, with each tremor above 0.5 “being treated as major news, heightening public concern”.
He added: “It is the case that across the country the British Geological Survey [BGS] has recorded far higher and greater seismicity which goes completely unnoticed and unreported, whereas the smallest of power cuts in Blackpool have been wrongly attributed to our work. The authors of the report upon which the current seismic traffic light system is based were clear that the threshold value of 0.5ML could be adjusted upwards over time.
“It may well be that we have reached that time not only for the UK shale gas industry, but also to address the concerns of local people who are becoming increasingly worried by reporting of tiny movements in the eart, which occur thousands of times across the UK every day as if they were harmful earthquakes.”
Cuadrilla said that 2ML was an appropriate limit because earthquakes of that magnitude “would not be generally felt at surface” and also the BGS definition was that anything below 2 was considered microseismicity.
Claire Perry, the energy minister, wrote in July that the limit had been set at a “cautious” level and that as experience of fracking developed it could be “adjusted upwards without compromising the effectiveness of controls”.