Rules surrounding the seismic impact of fracking are unnecessarily restrictive and should be closer to those for activities like quarry blasting, researchers say.
The measures were brought in by the Department of Energy and Climate Change to curb tremors from the controversial method of shale gas extraction after two small earthquakes were felt near Blackpool, Lancashire, in 2011 following an attempt by energy firm Cuadrilla to frack for shale gas.
Dr Rob Westaway and Professor Paul Younger from the University of Glasgow’s School of Engineering said the risk of serious earthquakes caused by fracking is lower than feared, but the seismic restrictions require the shutting down of operations which cause surface vibrations greater than magnitude 0.5 on the Richter scale.
Dr Westaway said: "That level of vibration is extremely low. To put it in perspective, if regulations for other vibration-causing activities were similarly restrictive you'd have to prevent buses from driving in built-up areas or outlaw slamming wooden doors."
Fracking – or hydraulic fracturing – involves pumping water, chemicals and sand at high pressure deep underground to fracture shale rock and release the gas trapped in it.
Dr Westaway said that by analysing the seismic waves caused by fracking, they had determined a scale of activity that would create surface vibrations within the limits already allowed by quarry-blasting regulations.
"For example, induced earthquakes of magnitude 3 from fracking activities 2.5km (1.6 miles) below the Earth's surface will create surface vibrations similar to the limits allowable from quarry blasting,” he said.
"Conversely induced earthquakes at the current UK regulatory limit of magnitude 0.5 would be expected to produce vibrations in a person's home that are smaller than those typically caused by the movement of buses or lorries past the end of their garden and comparable to many other widely-accepted forms of 'nuisance' vibration."
In a paper published in the Quarterly Journal of Engineering Geology and Hydrogeology, the engineers also said the longest fracture that could be caused by fracking was 600m long as a result of the amount of fracking liquid available.
A 600m-long fracture created in a single rupture was "very unlikely" and would correspond to a maximum quake of magnitude 3.6.
Prof Younger said: "That might be sufficient to cause minor damage on the surface such as cracked plaster. Again, however, there is already regulation in place for compensation for similar incidents caused by RAF fly-bys or mining operations. We'd suggest it would make sense for similar schemes to be put into place for fracking."
He also said the biggest cause of serious seismic accidents in fracking operations around the world was not from drilling or fracking itself but from disposing waste water back into the borehole after the process, which can cause earthquakes.
"In Britain, we've adopted long-standing EU groundwater regulations which bar sub-surface disposal of waste water completely, meaning there is no danger of this sort of event happening here. Instead, the water would be treated and disposed of safely elsewhere."
A spokeswoman for the Department of Energy and Climate Change said: "The threshold was set on the basis of a report by a group of independent experts. Our robust regulatory regime will allow shale exploration to take place while keeping the public safe."