The company sought to play down the impact of its activities, saying it had probably triggered "a number of minor seismic events". But Stefan Baisch, one of the report's authors, admitted the actual number was 50.
Mark Miller, Cuadrilla's chief executive, accepted 50 sounded like a lot of tremors but dismissed their significance. "There's a certain level of seismic activity that can occur even with a truck going past a house," he said.
"But just because it doesn't do any damage, doesn't mean we're not concerned about it. It's not good for us if the public is concerned and it's not good for the production of gas."
Cuadrilla stopped fracking at its site in Weeton and commissioned yesterday's report into whether the practice causes seismic activity on May 31, after concerns were raised about the tremors.
David Loveday, a shale gas expert at the Inenco energy consultancy, said the report demonstrated a "pressing need to understand the mechanism which potentially caused these earth tremors to prevent a re-occurrence".
A spokesman for the Department of Energy and Climate Change (DECC) said: "The implications of this report will be reviewed very carefully before any decision on the resumption of these hydraulic fracture operations is made."
The findings coincided with a day of environmental opposition to the practice, as protesters from the Frack Off campaign group occupied another Cuadrilla site near Southport, shutting it for the day. Frack Off also staged a rally in London to "highlight the hypocrisy" of a Shale Gas Environmental Summit taking place there. They argued that the £1500-ticket ($3000) event was "a blatant piece of 'Greenwash' designed purely to attract investors".
Before the publication of the report, which was conducted by independent experts, Cuadrilla had stressed that there, "was no proven link between the seismic events and the hydraulic fracturing". Yesterday, it was forced to concede 50 such events had occurred in eight months.
The company said: "The seismic events were due to an unusual combination of geology at the well site coupled with the pressure exerted by water inject. This combination of factors was extremely rare and would be unlikely to occur together again."
The report stressed while a "worst-case scenario" could result in a magnitude 3 earthquake in the Blackpool area, this "would be unlikely to occur" and, if it did, "there is no threat to people or property". Cuadrilla claimed an earthquake of 2.6 on the Richter scale would be "the maximum level allowed".
Dr Brian Baptie, a seismologist at the British Geological Survey, which is advising DECC on whether to allow the resumption of fracking in the UK, said: "Fifty seismic events does seem a lot, but most were very, very small."
He added that a magnitude 2.6 earthquake, at this depth, would not cause any structural damage but "might cause strong shaking that would be widely felt by people indoors and out".
Cuadrilla is at the forefront of shale gas exploration in Britain and raised hopes for the future of the industry in September when it revealed its field in Lancashire contained up to 5660 billion cubic metres. About a fifth is expected to be economically recoverable, providing enough gas to fuel the country for about 11 years.
- Independent
