Hydraulic fracturing during natural-gas extraction caused two earthquakes in the United Kingdom that were felt by residents, by reactivating a geological fault that had lain dormant for many millions of years.

Credit: Global Warming Images/Alamy

'Fracking' involves injecting a mixture of water, sand and chemical additives into the ground to fracture rock and loosen trapped natural gas. Earthquakes induced by the process in North America have been felt by communities, but this is the first such example in Europe.

A team led by Huw Clarke of fracking company Cuadrilla Resources in Lichfield, UK, reports that fracking in 2011 near Blackpool caused earthquakes on 1 April and 27 May of magnitudes 2.3 and 1.5, respectively. Fluid injected during the fracking operation (pictured) caused movement in a fault that had been inactive for 260 million years.

Geophys. Res. Lett. http://doi.org/xc9 (2014)