I think it's safe to assume that by the time an energy company is admitting problems, it's generally much worse than they admit. They say no greater than 3.0? I say, batten down the hatches:

Following seismic tremors in North-West England this Spring, the firm exploring for natural shale gas in the region has admitted that the disturbances were caused by the controversial exploration process of fracking.

Fracking involves cracking or fracturing rock, containing trapped shale gas, by using pressurized liquid. Shale gas is an increasingly important energy resource though there have been claims that it is worse for the environment than coal, largely due to the fracking process.

A press release from Cuadrilla Resources, who were responsible for exploration in the region, reported that:

"The hydraulic fracturing of Cuadrilla’s Preese Hall-1 well did trigger a number of minor seismic events.""The seismic events were due to an unusual combination of geology at the well site coupled with the pressure exerted by water injection as part of operations."

The company did add that the chances of such an occurrence happening again would be slim. It predicted that a worse case scenario would result in an earthquake measuring no more than 3.0 on the Richter Scale.