A microseismic event measuring 2.1 ML (local magnitude) on the Richter scale occurred at Preston New Road, according to the UK shale gas company Cuadrilla Resources.
"This lasted for around 1 second and resulted in ground motion less than 1.5 mm/s. Hydraulic fracturing was not taking place at the time", a company spokeswoman stated.
According to local media reports, the trembling was "the largest [to be] detected" at the UK's only active fracking site.
"We can confirm that a microseismic event measuring 1.55ML on the Richter scale occurred after we had completed the hydraulic fracturing programme for the day at our Preston New Road site. Most local people will not have felt it due to its small size. The equivalent ground motion would be similar to a large bag of shopping dropping to the floor. Well integrity has been verified and we will now pause operations and continue monitoring for the next 18 hours", the spokesperson said on 22 August, as quoted by a statement.
Earlier in August, the company began fracking its second well, as the first one was abandoned due to frequent quakes prompted by the company's activities. One of the strongest ones, measuring 1.5 ML on the Richter scale, was recorded at the Little Plumpton site in December 2018.
In 2016, the UK government allowed Cuadrilla Resources to begin fracking operations at the Preston New Road site, but protests by environmental activists repeatedly forced the company to suspend the project.
The British government claims that shale gas extraction could benefit the UK economy and contribute to Britain's net-zero emissions goals, and that the United Kingdom has "world-leading regulations" guaranteeing the safety and environmental responsibility of shale gas exploitation.
Fracking, or hydraulic fracturing, is a drilling technique used to extract gas with water and chemicals from shale deposits. The United Kingdom is reported to have vast shale gas resources, but extraction by fracking is widely objected to due to risks of polluting groundwater with chemicals.