I Feel the Earth Move: Earthquakes in the UK
The Government’s recent 'indefinite suspension' of fracking brought earthquakes into the news. So, it seems right to re-visit the earthquake risk in the UK. You might be surprised to learn that it is a serious risk – look up the National Risk Register and you’ll see that it gets 2 pages to itself. It can be accessed here.
What’s the connection with fracking?
The suspension came about after fracking operations in Lancashire caused an earthquake of magnitude 2.9 on the Richter Scale* along with several other ones of slightly lower magnitude. And 'caused' is the right word, by the way. The event is listed on the British Geological Survey’s website as 'induced seismicity' caused by fracking – a definitive attribution by the national authority.
To understand how this happens you need to know how fracking works. Basically, a mixture of liquids, sand and chemicals is blasted into underground shale under very high pressure. This fractures the rock or widens its existing fissures, which allows the gas and oil within it to be extracted. It’s fair to say that the local communities hate it, and some 250 protest groups are campaigning against it energetically.
It’s not just the earthquake connection. The process causes air pollution and vast quantities of dangerously contaminated wastewater. So, concerns tend to focus on public health and the environment. In fact, the process is so aggressive that it seems almost intuitively wrong. But there is also a sub-text to this public outrage. People seem to sense that their communities are in danger of being steamrollered by the sheer financial and political power of an industry they don’t entirely trust.
Two official reports triggered the Government’s action. The National Audit Office challenged the industry’s claim that fracking would ever produce gas in 'meaningful quantities' or reduce prices. Then the Oil and Gas Authority (the government regulator) confirmed that it is not possible to predict the location or intensity of the earth tremors it causes. In other words, it’s not safe.
These reports were what one business journalist called a 'hammer blow' to the industry. The other serious impact for local authorities is the scale of popular unrest and protest. Policing at the fracking site at Preston New Road has been very expensive, with one report giving the figure of £12 million so far. The operator, Cuadrilla, now seems to be on the back foot, resorting to nationalistic rhetoric about using 'our own' gas rather than relying on 'foreign imports'.
So how does an earthquake of 2.9 magnitude compare to the way the risk is modelled in the National Risk Register? And what is the historical record of UK earthquakes?
As the regulations stand there is a maximum safe limit of magnitude 0.5; any earth tremor bigger than that puts a stop to fracking operations – so 2.9 is well in excess of that threshold.
Regarding naturally-occurring earthquakes in the UK, they are more common than you might think. Visit the British Geological Survey’s website and you will find a list of earthquakes in the British Isles over the last 50 days. The list is currently giving details of 21 quakes, ranging in magnitude from 0.3 to 2.4. (That was between 2nd October and 17th November 2019).
The last one big enough to be of interest to emergency managers was in 2008, near Market Rasen in Lincolnshire. It was magnitude 5.2 and was felt as far away as the south coast of England and in Northern Ireland. It caused significant structural damage and one person was injured. Insurance pay-outs for property damage are estimated at £30 million and fire crews responded to 50 incidents and 1 fire that were direct consequences of the earthquake. A year before, in Kent, there was one of magnitude 4.3. That one caused one injury and damaged nearly 500 properties – mostly in Folkestone. 73 houses were too badly damaged for people to move back into.
Research suggests that a magnitude of 6.5 is probably the maximum we could get, given our geology. This is because we are not close to a tectonic plate boundary and 'intraplate' seismic events like ours naturally tend to be less severe. This estimate is close to the biggest one on record, which was a 6.1. The epicentre was 60 miles out in the North Sea on the Dogger Bank and it happened in 1931. The effects were felt across the whole country and in France, Belgium and the Netherlands. Hundreds of properties were damaged in many east coast towns and there was one related death. It also created a 'small non-destructive tsunami'.
The key point in this is that if it had happened onshore and close to a built-up area, the damage would have been very significant. Buildings would almost certainly have been destroyed and lives lost. So, the earthquake risk is worth taking seriously and doing something about.
At the local level that means generic planning and capability development, to deal with the common consequences – mostly arising from collapsed buildings and other structural damage. At the national level building and design regulations protect critical infrastructure like power stations, nuclear facilities and petrochemical plants. There is also on-going research and monitoring.
But can they be predicted?
The United States Geological Service (USGS) is both economical and definitive on that:
“No. Neither the USGS nor any other scientists have ever predicted a major earthquake. We do not know how, and we do not expect to know how any time in the foreseeable future.”
* The Richter Scale is not the only index of earthquake severity. However, it is the one in most common use and so it is used exclusively in this post.