Reactions to news that a 0.8 magnitude tremor occurred near Lancashire fracking site on the 26 October.
Dr Brian Baptie, Head of Seismology at the British Geological Survey, said:
“Today’s magnitude 0.8 ML event was detected on the network of sensors deployed by the British Geological Survey (BGS) around Preston New Road to provide an independent assessment of any induced seismicity. It was around 200 times smaller than the magnitude 2.3 ML event that stopped operations at Preese Hall in 2011. The maximum recorded ground motion was around 0.1 mm/s. This is well below the limits set for blasts from quarry operations (6 mm/s). On average there are around 20-30 earthquakes with a magnitude of 2 ML or greater every year somewhere in the UK. Because the number of earthquakes increases as magnitude decreases, we might expect around one thousand earthquakes with a magnitude of 0.8ML or above every year across the UK.”
Prof Ernest Rutter, University of Manchester, said:
“After the Preese Hall earthquakes in 2011 the monitoring arrangements at Preston New road are probably the most comprehensive anywhere, therefore very small events like these (at less than ML 1.0) are being detected. Elsewhere they would likely not be picked up. The traffic light system employed is set at very cautious levels, and Cuadrilla do seem to be playing strictly by the book.
“Note it is not fracking per se that causes tremors, but the unwanted escape of injected fluid into nearby cracks and faults that may be accessible and suitably oriented to be able to slip by a few millimetres, that is why they can potentially be controlled by adjusting the fluid injection rate and maximum pressure.”
Prof Stuart Haszeldine, Professor of Geology at the University of Edinburgh, said:
“This larger tremor means that operations will be suspended for at least 18 hours. UK fracking traffic lights are on red for the first time!
“There is a clear trend, that the energy released by each of these tremors is increasing through the week. Although all of these are still very small events and can only be detected with instruments.
“But there will be two Big Questions over the next few days. Is enough energy left in this piece of ground that Magnitude 2 and 3 events will occur? And have the underground displacements damaged the borehole, so that gas can leak to the big fault penetrated by this borehole, and up towards aquifers?”
Dr Stephen Hicks, Postdoctoral Research Fellow in Passive Source Seismology at the University of Southampton, said:
“The magnitude 0.8 earthquake triggered on 26th October now means that fracking operations will be suspended for at least 18 hours following the event. This microseismic quake won’t have been felt at the surface, but the pause for 18 hours allows for the chance of any “trailing” i.e. delayed (+ possibly larger) events, and for the operator to possibly re-adjust their fluid injection parameters ready for resuming operations later. A new M 0.5+ “trailing” event over the next 18 hours would generate a new “red” (as if it had happened during injection), and a further 18 hour period would need to elapse before operations can resume.”
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None to declare.