Cuadrilla has pledged to restart fracking for shale gas at its site in northern England on Monday in spite of a second earth tremor in two days.
The energy company was forced on Friday to halt its operations near Blackpool — which involve pumping water into shale rocks several kilometres underground at high pressure to extract gas — after a tremor of 0.76 on the Richter scale.
A slightly larger tremor of 0.78 — undetectable at ground level — happened on Saturday, after the company had ceased operations at the Preston New Road site at 1pm.
In total, there have been 18 tremors in 12 days since Cuadrilla resumed fracking this month after a seven-year hiatus.
In 2011 the company was forced to stop fracking after a series of tremors measuring up to 2.3 on the Richter scale.
Fracking for oil and gas has revolutionised energies supplies in the US, but the nascent UK industry has run into strong opposition from environmental protesters. The Labour party has indicated it would ban fracking.
Cuadrilla’s activities are monitored through a “traffic light” system supervised by the Oil and Gas Authority, which regulates the UK energy industry.
A tremor above 0.5 on the Richter scale while fracking is taking place — as happened on Friday — constitutes a “red light” that requires operations to be halted for 18 hours.
A spokesman for Cuadrilla said the tremor on Saturday was “not a ‘red’ incident under the traffic light system operated by the Oil and Gas Authority as we were not pumping fracturing liquid as part of our hydraulic fracturing operations at the time”.
He added: “However, we will, as always, continue to monitor the seismic activity closely and plan to resume hydraulic fracturing on Monday.”
The Oil and Gas Authority said it was aware of the latest incident. “Hydraulic fracturing is known to cause minor seismic events of this magnitude,” said the authority.
“While the operations at the Preston New Road site have been designed to minimise any disturbance, minor events like these were expected.”
Friday’s tremor was the first to trigger a “red light” — the previous ones were either too small to stop fracking or occurred after Cuadrilla’s operations had ceased for the day.
If a tremor of zero to 0.49 on the Richter scale is measured during fracking, it prompts an “amber light” that requires the company to ease off activities without stopping them completely.