Cuadrilla temporarily halted fracking at its site in Lancashire after a “tiny” tremor was detected, the energy company has said.
The “extremely low level” of seismic activity – around 0.4 local magnitude – was detected on Tuesday afternoon at the shale exploration site at Preston New Road while fracking operations were taking place.
While it was too low to be felt at the surface, it is classed as an amber event as part of the traffic light system in place for monitoring seismic events during operations.
Cuadrilla said it was required to reduce the rate at which it was pumping fracturing fluid once the seismic event had been detected, but it had “adopted extra caution” and had stopped pumping for the day in response.
Fracking is set to resume on Wednesday morning, the company said.
In a statement, Cuadrilla said: “Seismicity will, as always, continue to be monitored closely around the clock by ourselves and others and we plan to continue hydraulic fracturing again in the morning.
“Local residents should be reassured that the monitoring systems in place are working as they should.
“These are tiny seismic events that are being detected by our monitors as we fracture the shale rock and are not capable of being felt, much less cause damage or harm.”
The controversial fracking process got under way earlier this month after an environmental campaigner failed in a High Court bid to block operations.
The exploration taking place at Preston New Road is the first fracking in the UK for seven years, after work by Cuadrilla was halted in 2011 following two tremors near Blackpool.