The British Geological Survey recorded a small earth tremor today near Cuadrilla’s fracking site on the edge of Blackpool. This follows three micro-seismic events yesterday.
The seismic activity, the first recorded in the area since fracking began on Monday (15 October 2018), was too small to be felt at the surface.
But today’s event had a magnitude of 0.3ML, which would have put it in the amber zone of the regulations on induced seismicity had it occurred during fracking.
Under the rules, known as the traffic light system, operators are required to “proceed at caution” in amber. Fracking must stop immediately if seismic events reach 0.5ML (the red level).
The rules were introduced after fracking at Cuadrilla’s shale gas well at Preese Hall in 2011 was linked to earthquakes measuring 2.3 and 1.5.
Yesterday’s micro-seismic events measured -0.2, -0.8 and -0.3 magnitude.
All the activity was clustered on the edge of Blackpool, near the junction of A583 and Peel Road. This is the area approximately at the end of the horizontal shale gas well, called PNR1z, currently being fracked by Cuadrilla.
The first event was recorded at 4.48pm (BST) yesterday, followed by two others later at night at 11.54pm and 0.44am (both also BST). The depths were estimated by the BGS at 2km and 3km. Cuadrilla is fracking at a depth of about 2.2km.
Today’s event was at 2.20pm (BST) at an estimated depth of 3km.
Yesterday’s events were too small to show up on Cuadrilla’s online display of seismic data. This shows activity only in the amber and red zones of the traffic light system.
A spokesperson for Cuadrilla told us today’s 0.3ML event would also not be shown on the display. It was classed as a “trailing event” because fracking was not actually taking place:
“If we had been pumping at that time it would have indeed been an amber event we would have confirmed it.”
On yesterday’s events the spokesperson said:
“Three microseismic events were detected yesterday by the highly sensitive Traffic Light System Cuadrilla has installed around the Preston New Road site and were very far below levels that could be felt at surface. The recordings from these seismometers are shared with the British Geological Survey to help them reassure the public that operations are continuing safely as planned.
“We take the monitoring and regulation of seismicity seriously, with daily reports sent to the regulators. The microseismic events recorded were extremely low and well within the Green Light threshold and confirm that the monitoring system is working to the highest standard.”
DrillOrDrop asked the company whether it was fair to say that the events were caused by fracking. The company’s spokesperson said:
“Events of this magnitude cannot even be described as tremors. To do so implies some felt movement at surface and micro seismic measurement confirms this is simply not the case We’ve been monitoring baseline seismicity for some time in the run up to starting hydraulic fracturing operations, and we have noted fluctuations at this very low level of microseismicty during that time. What we do know is that our detection systems are working as planned and these very low levels of seismicity are being detected.”
We also asked when the most recent hydraulic fracture treatment took place. Cuadrilla said:
“The most recent stage was completed yesterday and our hydraulic fracturing operations are continuing as planned.”
The Southampton University geologist, Dr Stephen Hicks, who has been monitoring a recent swarm of earthquakes in Surrey, tweeted:
“These are tiny “microseismic” events (not felt at the surface) and to be expected as they are probably caused by the brittle failure of small volumes of rock due to the hydraulic fracturing process. It’s good that the BGS network has such a small detection threshold.”
Dr Nick Riley, commenting on the micro-seismicity, said:
“The -0.8 event corresponds in terms of energy released to a person of average weight at 75kg jumping onto the ground from a height of 2m.”
David Smythe, emeritus professor of geophysics at University of Glasgow, who opposed Cuadrilla’s shale gas plans in Lancashire, said the events could be a warning sign:
“Recent research by Stanford University shows that these tiny tremors can be indicators of bigger quakes to follow – like canaries in a coal-mine. The problem for Cuadrilla is that if it carries on regardless, bigger earthquakes may well be triggered. To quote Cole Porter; “There may be trouble ahead”. Cuadrilla’s only safe option is to cease fracking.”
A spokesperson for the campaign group, Frack Free Lancashire said:
“We will continue to monitor these events closely. Considering the relevant past history with the Fylde Coast’s geology and having two significant seismic events which effectively shut down the fracking industry, all eyes are currently on Cuadrilla. These events may be dismissed as being minor and “can’t be felt” but what occurs under the earth is beyond anyone’s control.”