Terrawatch: warnings fail to prevent UK fracking quakes

Why didn't a traffic-light scheme stop the recent fracking-induced tremors near Blackpool?

In theory, the chances of your house being shaken by a fracking-related earthquake are incredibly slim. In the UK, a traffic-light system is designed to minimise the risk of larger quakes occurring, with fracking halted if a tremor of magnitude 0.5ML (local magnitude) or above is recorded. So last week's 2.1- and 2.9-magnitude fracking-related tremors near Blackpool came as a surprise, given a "red-light" 1.55-magnitude quake had occurred the previous Wednesday, and fracking at Cuadrilla's Preston New Road site had been suspended.

"It suggests that the traffic-light scheme, even with what seemed like a conservative limit of [magnitude] 0.5, might not be appropriate," says Stephen Hicks, a seismologist at Imperial College London. Trials in Finland have shown traffic-light schemes can help prevent quakes, so why didn't it work on this occasion?