https://phys.org/news/2018-10-uk-fracking-firm-cuadrilla-drilling.html

The British Geological Survey recorded the 0.8-magitude quake just after 11:30 a.m. Friday. It followed several smaller tremors earlier in the week.

Under U.K. rules, any tremor over 0.5 is classed as a "red event" and sparks a temporary shutdown while monitoring continues.