Should earthquakes stop fracking?
The word earthquakes invokes a suitably dramatic, disaster movie type response. Earthquakes have been caused by fracking (notably in 2011 around Blackpool, an area of low natural seismicity even by UK standards) as reports by both the company involved, Cuadriulla Resurces, and the UK government concluded. "Anything else would be a surprise," says Joseph Dutton of the University of Leicester. "You're taking something out of the ground so something's going to shift - that's basic geology." Is this a significant worry that provides a legitimate argument to curtail fracking?
The strongest earthquake measured at Blackpool was 2.3 on the Richter scale. this magnitude of earthquake is felt slightly by some people and there is no damage to buildings. There are over 1 million of this size of earthquake globally each year. There have been many instances in the past of larger earthquakes than this being caused by human activity, e.g.: mining (including the settling of abandoned mines), oil-field depletion, filling reservoirs with water, injecting water into the ground for geothermal power, waste disposal, atomic bomb tests. Impounding water in reservoirs has caused 39 earthquakes of magnitude up to 7.8 (around roughly 400,000 times more powerful than Blackpool).
"The energy released during hydraulic fracturing is less than the energy released by the collapse of open voids in rock formations, as occurs during coal mining. The intensity of seismicity induced by hydraulic fracturing is likely to be smaller due to the greater depth at which shale gas is extracted compared to the shallower depth of coal mining." (The Royal Society and The Royal Academy of Engineering, 2012, ‘Shale gas extraction in the UK: a review of hydraulic fracturing'). " The report goes on to comment on the geological factors that will mitigate against large earthquakes when fracking: "The properties of shale provide natural constraints on the magnitude of seismicity induced by hydraulic fracturing. Different materials require different amounts of energy to break. Shale is relatively weak. Stronger rocks will generally allow more energy to build up before they break, generating seismic events of larger magnitude."
Associating seismic activity with fracking is correct, but it is clear that the media headlines it is generating are more shocking than reality.
This is just one of the stories from my energy talk