On small earthquakes in Sussex

By Kevin Turner, Principal Lecturer, Brighton Business School

The controversial technique called hydraulic fracturing or ‘fracking’ has transformed US oil and gas output with major benefits for the economy and particularly manufacturing industry. A recent report by the consultancy IHS cited in The Economist [1] predicts a $533 billion boost to US GDP by 2025 creating around 3.9 million jobs. However, despite the generally accepted economic benefits of fracking, public opinion in the UK remains cautious.

Kevin Turner, Climate Change and Global Business Operations module leader, considers whether fracking-related activity is likely to trigger earthquakes.

Shale rig and gas well

Shale rig and gas well. Source: WCN 24/7

During the summer of 2013 the village of Balcombe in Sussex, a few miles north of Brighton, became the centre of national media attention due to environmental protests. The protestors were drawing attention to the test drilling for oil and gas by a small energy company, Cuadrilla Resources, who have been exploring potential sites for onshore gas recovery by fracking. One of the concerns raised by the protestors was that the drilling may lead to earthquakes, which had led to suspension of similar drilling by Cuadrilla near to Blackpool in 2011. The larger of the two earthquakes recorded in that case was magnitude 2.3. [2]

How serious is a magnitude 2.3 earthquake? The British Geographical Survey publish data about all earthquakes recorded in the UK [3]. During the period from 6th July to 12th August 2013, while the protests were at their height, there were 11 earthquakes in the UK. The most intense was magnitude 2.8 at Gairloch in the Highlands of Scotland. A similar earthquake with identical magnitude had occurred two months earlier at the same place – a local resident said that “he had felt the walls of his house shudder as if a large bus had passed by outside”. [4]

Could hydraulic fracturing result in worse earthquakes than this? A journal article by scientists from the universities of Durham and Keele was published in Marine and Petroleum Geology in 2013. [5] They studied reports of 198 possible instances of earthquakes “induced” by human activity. Of the three earthquakes attributed to hydraulic fracturing the largest was magnitude 3.8 in Horn River Basin, Canada. Their conclusion was:

‘Hydraulic fracturing of sedimentary rocks, for recovery of gas from shale, usually generates very small magnitude earthquakes only, compared to processes such as reservoir impoundment, conventional oil and gas field depletion, water injection for geothermal energy recovery, and waste water injections.’

So there was no scientific basis for the protestors concerns. They ran far more risk of being run over by a truck than of being harmed by an earthquake.

[1] “American industry and fracking: From sunset to new dawn”, The Economist, 16 November 2013 http://www.economist.com/news/business/21589870-capitalists-not-just-greens-are-now-questioning-how-significant-benefits-shale-gas-and
[2] “Fracking tests near Blackpool ‘likely cause’ of tremors”, BBC 2 November 2011, http://www.bbc.co.uk/news/uk-england-lancashire-15550458
[3] http://www.quakes.bgs.ac.uk/earthquakes/recent_uk_events.html
[4] “Gairloch earthquake ‘felt like a big bus’”, BBC 16 May 2013, http://www.bbc.co.uk/news/uk-scotland-highlands-islands-22551808
[5] “Induced seismicity and hydraulic fracturing for the recovery of hydrocarbons”, Richard Davies, Gillian Foulger, Annette Bindley & Peter Styles, Marine and Petroleum Geology, 45 (2013) 171-185

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