British shale gas company Cuadrilla has paused fracking at its Preston New Road site in Lancashire, northwest England, due to an earth tremor late on Aug. 21.

Cuadrilla, which restarted fracking at the site last week, repeatedly had to stop operations last year under Britain’s traffic light regulation system, which immediately suspends work if seismic activity of magnitude 0.5 or above is detected.

“We can confirm that a microseismic event measuring 1.55 ML [local magnitude] on the Richter scale occurred after we had completed the hydraulic fracturing program for the day at our Preston New Road site,” Cuadrilla said in a statement.

It said the well’s integrity had been checked and operations would be paused for 18 hours, as per the rules.

Fracking, or hydraulically fracturing, involves extracting gas from rocks by breaking them up with water and chemicals at high pressure.

Following last year’s stop-start operations Cuadrilla said it is using a thicker fracking liquid this time round, which it hoped would lead to fewer seismic events.

The government last week signaled support for the industry and is keen to cut the country’s reliance on imports of natural gas, which is used to heat around 80% of Britain's homes.

However, it is fiercely opposed by environmentalists who say extracting more fossil fuel is at odds with Britain’s commitment to reduce greenhouse gas emissions.

“Fracking just isn't part of the future if the government is serious about avoiding climate breakdown,” said Jamie Peters, campaigner at Friends of the Earth.

Britain in June became the first G7 country to enshrine in law a target to reach net zero greenhouse gas emissions by 2050, which will require less use of natural gas.

Cuadrilla is 47.4% owned by Australia's AJ Lucas, while a fund managed by Riverstone holds a 45.2% stake.

Onshore