One tremor was magnitude 0.3, the level beyond which experts say fracking has to proceed with caution

This article is more than 1 year old

This article is more than 1 year old

A series of small earthquakes have been detected in Lancashire close to the site where fracking operations began this week.

The British Geological Survey (BGS), which provides impartial advice on environmental processes, recorded four tremors in the vicinity of the energy firm Cuadrilla’s site on Preston New Road near Blackpool on Friday.

Fracking was stopped in 2011 after two earthquakes, one reaching 2.3 on the Richter scale, were triggered in close proximity to the site of shale gas test drilling. A subsequent report found that it was highly probable that the fracking operation caused the tremors.

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On Monday Cuadrilla began drilling again after campaigners lost a high court legal challenge.

The BGS said: “Since hydraulic fracturing operations started at Preston New Road, near Blackpool, we have detected some small earthquakes close to the area of operations.

“This is not unexpected since hydraulic fracturing is generally accompanied by micro-seismicity. The Oil and Gas Authority (OGA) has strict controls in place to ensure that operators manage the risk of induced seismicity.

“All of the earthquakes detected at Preston New Road so far are below the threshold required to cease hydraulic fracturing.”

One of Friday’s tremors measured 0.3, the level beyond which t he BSG says hydraulic fracking should proceed with caution. Tremors above 0.5 would force operations to cease.

Facebook Twitter Pinterest Police remove a protester attempting to prevent a lorry entering Cuadrilla’s site. Photograph: Oli Scarff/AFP/Getty Images

Ash Hewitson, of the anti-fracking campaign group Reclaim the Power, said: “As well as facing growing local, national and political opposition, these recent earth tremors are proving what we’ve know all along - that fracking is too risky.

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“As operations on the site continue the impacts on seismic activity will only increase. Cuadrilla should stop now before they cause any real damage and the government should rally behind the local people and give them what they want - access and support for community energy and renewables.”

Fracking is a method of extracting natural gas by injecting fluid into a well under high pressure to fracture gas-bearing rocks deep underground.

In the US, where shale gas production has increased rapidly in recent years, the introduction of fracking in Oklahoma coincided with a rise in the state’s earthquake risk. The practice has also been linked to large earthquakes in Alberta, Canada.

This week three environmental activists – Simon Blevins, 26, Richard Roberts, 36, and Rich Loizou, 31 – who became the first people to be jailed for an anti-fracking protest in the UK, returned to the Lancashire site after being released from prison.

An appeal judge found that their sentences of more than a year in prison each were “manifestly excessive”.

Facebook Twitter Pinterest Rich Loizou, Richard Roberts and Simon Roscoe Blevins return to Cuadrilla’s fracking site. Photograph: Christopher Thomond/The Guardian

The Preston New Road site has been a focal point for protests since the government overruled Lancashire county council and gave Cuadrilla permission to extract shale gas at two wells on the site in October 2016.

Hundreds of people were due to gather at the site on Saturday to protest against fracking and climate change.

Cuadrilla said: “The micro seismic events which have been recorded through the detailed monitoring Cuadrilla and the BGS are carrying out are successfully detecting events even at these very low levels.

“This is not an ‘amber’ incident under the traffic light system operated by the OGA as we were not pumping fracturing fluid as part of our hydraulic fracturing operations at the time and the seismic events remain under 0.5 local magnitude.”