A temporary ban on fracking was imposed after two tremor in Lancashire in 2011

Fracking baseline study to help measure seismic impact

A study designed to provide a baseline to measure the seismic impact of fracking has found that the UK experiences just a handful of 'man-made' earthquakes a year.

The analysis of 1,769 seismic events between 1970 and 2012 of 1.5 magnitude and above - the minimum detectable threshold - suggests that at least 21 per cent were caused by human activities.

But the majority of these were due to coal mining and there has been a sharp decline in the number of earthquakes since the 1980s, when the coal industry collapsed, and the average number of onshore earthquakes caused by human activities since 1999 is three, the paper published in The Journal Marine and Petroleum Geology found.

Professor Richard Davies of Newcastle University, who led the research, said it provided the world's first baseline for the impacts of fracking in the UK before use of the process is ramped up as part of the Government's pledge to go "all out for shale".

"Earthquakes triggered or induced by humans are not a new concept for us here in the UK, but earthquakes related to fracking are," he said. "Understanding what the current situation is and setting a national baseline is imperative, otherwise how can we say with any confidence in the future what the impact of fracking has been nationwide?"

Concerns about the seismic impact of fracking are regularly voiced by opponents to the technique, especially since two tremors caused by fracking in Lancashire in 2011 that resulted in a temporary ban being imposed on the practice.

Davies said: "Historically, fracking-related earthquakes have been small, but the UK is criss-crossed with faults - some of which may be critically stressed - and if triggered these could result in earthquakes that people can feel."

He added that the national baseline, along with seismic monitoring at fracking sites, could show the impact of shale gas exploration on the number of earthquakes that occur in the UK.

"If widespread exploitation of the UK's shale reservoirs is granted and numbers consistently rise then, in conjunction with local monitoring data, we should be able to confidently demonstrate a causal link," he said.

The study by experts from Newcastle, Durham and Keele universities as part of the Researching Fracking in Europe consortium looked at around 8,000 onshore seismic events recorded by the British Geological Survey between 1970 and 2012, with a range of origins including mining, industrial explosions, natural causes and lightning strikes.

Only 1,769 of these events were above the 1.5 magnitude threshold, but at least 21 per cent were related to human activity. Some 40 per cent were natural occurrences and 39 per cent were 'undefined', but even taking the latter into account, the average number of man-made events is just 12 a year.

A spokesman for the Department of Energy and Climate Change said: "As recognised by this research, there are no documented cases of shale gas operations causing subsidence or earthquakes which have caused damage at the surface.

"We have extremely robust controls in place to mitigate seismic risks and in the unlikely event that any operations were to pose a risk, we have the powers required to close them down."

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