The British Geological Survey confirmed there were two more small earthquakes in Surrey today – both in the same place as the previous cluster.
This brings to 10 the number in the county since April 2018. Before then, earthquakes had not been recorded in Surrey for 50 years.
Today’s first earthquake was just before 5am British Summer Time and had a magnitude of 1.7, later raised to 2.0. The second was at 2.33pm BST, and measured 2.7. Both were felt by residents in the Newdigate and Charlwood areas of Surrey. There were also two aftershocks.
The cluster of earthquakes has prompted calls by some local people for an investigation into any links with the local oil and gas industry. A public meeting has been planned for 25 July 2018 in Brockham, where Angus Energy operates an oil production site.
Last week, the British Geological Survey installed two seismic monitors to track the earthquakes (DrillOrDrop report). One is at Russ Hill, directly above the current best estimate for the epicentres. The second is in the Norwood Hill/Horley area, near another oil exploration site at Horse Hill.
Yesterday, the managing director of Angus Energy, Paul Vonk, rejected any link with the Brockham oil site.
Mr Vonk, speaking in an online interview with Zak Mir, said:
“It is scientifically and physically impossible for us to have caused these tremors.
“Of course, tremors in an area of southern England where they haven’t been in ages, you know, is news.”
Mr Vonk said:
“Basically, the way the faulting structure works, it works from east to west. We, at the reservoir at Brockham, are working at a third of the pressure that you can actually activate faults. So we can’t do it with our current reservoir.
“But even hypothetically, if we could do it, the stresses would go east-west. The epicentre of the tremors was 10.5km south of us.”
“The BGS is doing some extra work and in time it will be proven by the authorities that it isn’t us.”
Southampton University seismologist Dr Stephen Hicks, who helped to install the new seismic monitors, said today on Twitter:
“Location, depth & magnitude confirmed – new stations allow for much better estimates, especially for depth. Magnitude 1.7 and at about 1km depth, with an epicentre location close to the previous estimates for the earlier quakes in the sequence.”
“[About] 1km depth is fascinatingly shallow if you compare to most UK earthquakes which have depths >5km in the crust. To me 1km depth suggests that today’s event occurred in the softer sedimentary strata, rather than in the underlying crystalline “basement” rock.”