Tremors continue as data shows strongest seismicity followed Cuadrilla’s final frack

190902 events over 0.0 since fracking stopped Refracktion

Seismic events measuring 0.0ML or more recorded by the British Geological Survey since fracking stopped at Preston New Road on 23 August 2019. Map: Refracktion

Most of the strongest earth tremors caused by Cuadrilla’s shale gas site near Blackpool were after the company’s last frack, according to data from the British Geological Survey (BGS).

The BGS added another four earth tremors to its online database today.

They bring to 38 the number of tremors recorded since the company last carried out hydraulic fracturing at the Preston New Road site 10 days ago. They account for almost a third of the total since fracking began last month.

The two strongest tremors were after the final frack on the PNR2 well on Friday 23 August. Operations were suspended on Monday 26 August after the site caused the UK’s strongest fracking-induced tremor.

Four of the six strongest tremors, measuring 1.0ML or more, were after the last frack, as were the tremors with the strongest intensity, rated 4 and 6.

Of the total 128 tremors, none measuring 0.5ML or above happened when fracking was taking place. Six out of nine of these events were also after the final frack.

The strongest tremors recorded by the BGS while fracking pumps were running at PNR2 measured 0.0ML. This did not trigger a pause to fracking under the traffic light system (TLS) regulations.

190902 Recent tremors slider

Tremors since the last frack at Preston New Road on 23 August 2019. Map: DrillOrDrop

Three tremors were listed for today, measuring -1.0, 0.0 and 0.2, all early this morning. Yesterday, there was a -0.9 tremor at 7.42pm.

Cuadrilla has been visiting people who say their homes have been damaged by the tremors.

“Extensive data and analysis requested”

The industry regulator, the Oil & Gas Authority (OGA), said today it had written to Cuadrilla on Friday 30 August requesting “extensive data and analysis.”.

In a statement, the OGA said:

“Once provided, this data and analysis will assist the OGA’s full consideration of whether the assumptions and mitigations in Cuadrilla’s PNR 2 Hydraulic Fracture Plan continue to be appropriate to manage the risk of induced seismicity at the Preston New Road site.

“Hydraulic fracturing operations will remain suspended until the OGA’s considerations are complete.”

“Constantly on edge waiting for the next tremor”

A spokeswoman for Preston New Road Action Group, which represents local residents, said:

“Our environment has clearly been disturbed by Cuadrilla’s fracking. We are now constantly on edge waiting for the next tremor. The TLS in its current form has not prevented them, any move to weaken it would be a complete travesty.”

The region’s Green Party MEP, Gina Dowding, said:

“The residents of Preston New Road community and Lancashire deserve better. It is now clear that Cuadrilla have failed to work within the limits of the seismic traffic light system, and have caused damage to many residents’ property. This alone should be a massive red flag to the unsustainable elements of fracking in Lancashire and the UK.

“With another four tremors this morning, ten days after fracking took place, there should be an immediate ban on this industry.”

Controlling earth tremors

oga tls full

The Traffic Light System. Source:

The traffic light system (see above) requires a pause after seismic events during fracking that measure 0.5ML or more.

The hydraulic fracturing plan for PNR2 goes slightly further. It required Cuadrilla to pause fracking for 18 hours after any seismicity, whether during or following pumping, that measured 0.5ML or more.

Cuadrilla hydraulic fracturing plan

Hydraulic fracturing plan for PNR2 version 3.0. Source: Cuadrilla Resources

A system recommended by academics after tremors caused by fracking at Preese Hall in 2011 would have required longer pauses and other actions.

Under those proposals, a single seismic event of more than 0.5ML would require fracking to be shut down immediately, the well flushed and pumping stopped.

Any seismicity during or after fracking measuring less than or equal to 1.5ML would require the operator to flowback the well for a minimum of three days.

Stronger seismicity, measuring more than 1.5ML, would require a minimum of 10 days of flowback.

Professor Peter Styles diagram

System for mitigating fracking-induced earth tremors proposed by Professor Peter Styles after the Preese Hall earth tremors.

If there was no additional seismicity within 24 hours of 1.0ML or more, the operator had the option of refracking after three more days of flow back. If there was seismicity measuring more than 1.0ML in the next 24 hours, the operator must move on to the next stage.

The academics’ proposal was replaced by the then Department of Energy and Climate Change with the simpler traffic light system.

Had the alternative system been in place, Cuadrilla would have had to flow back the well for a minimum of 10 days after the 1.6ML event on 21 August.

Cuadrilla and the traffic light system

On 15 October 2018, the day fracking began at Preston New Road, the BBC’s Today programme asked Cuadrilla’s Francis Egan whether he could reassure people that the Preese Hall earthquakes, measuring 2.3ML and 1.5ML would not reoccur or be “something worse”. “Absolutely”, Mr Egan replied.

Within a fortnight, there was a red event under the traffic light system, measuring 0.8ML (PNR tremor tracker 2018). By the end of the month, the company said it was “about to choke” from regulations on tremors and it was calling for the 0.5ML limit to be relaxed.

In a statement on 15 August when the PNR2 fracks began, Cuadrilla said it would work in line with the TLS. After more than 100 tremors and the UK’s strongest fracking-induced seismic event, the company’s most recent statement said:

“We don’t have a date for operations to restart but it won’t be until both the regulator and ourselves are confident that the technical questions have been satisfactorily answered and the risk of a repeat occurrence has been properly mitigated.”

DrillOrDrop asked the company to comment on the likelihood of further tremors, any action it could now take to mitigate seismicity and the effectiveness of the traffic light system. The company said:

“We provided up to date information about our activities both past and ongoing on Saturday and we currently have nothing further to add.”

The campaign group, Frack Free Lancashire, said today:

“It is worth remembering that Cuadrilla originally stated that they could work within the traffic light system, that there would be no seismic events, that nothing would be felt at the surface and that there would be no damage to property as a result of their activities. They have been spectacularly wrong on every issue.

“Cuadrilla are now saying that they should be allowed to continue fracking once the suspension is lifted.

“Residents have now had enough. It is time for Cuadrilla to pack their bags and leave – for good. We do not wish to live in a sacrifice zone.

“We are calling for an immediate and permanent ban on all fracking.”

When was the final frack?

Cuadrilla said it fracked the PNR2 well on Friday 23 August 2019. People monitoring the site said the pumps stopped running at about 2.45pm (bst).

A 1.1ML tremor on Friday night would have required a pause for 18 hours under the company’s hydraulic fracturing plan. So there should have been no fracking on Saturday 24 August 2019. Fracking was not permitted at Preston New Road under the planning permission on Sunday or bank holidays.

The record-breaking 2.9ML tremor happened at about 8.30am on Monday 26 August. Within hours, the Oil & Gas Authority announced the suspension of fracking at Preston New Road.

Assuming there was no fracking after 2.45pm on Friday 23 August, the BGS data today shows there have been 38 tremors since then, out of a current total of 128.

DrillOrDrop’s Preston New Road 2019 tremor tracker 

Updated with OGA statement

11 replies »

  1. What concerns me is
    1. The damage they may have caused underground
    2, The water situation, Fracking requires thousands of gallons daily. When the water is used it is toxic. They should NOT put it back in the ground as it will kill wildlife and if it enters the water supply !!!!!!!!!!! There will be a medical emergency such as we have never seen befor. And if they pump it back out of see it will
    kill fish and marine wildlife.


  2. Water that requires treatment gets treated, mdk.

    Much the same as when you have a shower.

    One person who seems to think it okay to add waste into the sea, is a certain Swedish environmental campaigner.

    Somewhat ironic really.

  3. Thank you Ruth, a nice concise summary.

    I am curious and concerned of the latency of the seismic events and possible interaction of these earth movements be it on faults or bedding planes with other critically stressed faults in the region, potentially outside the fracture ‘arc’. So could a seismic event be induced on say the ‘Thistleton Fault’ sometime in the future due to stress transference?
    Seismic events outside the hydraulic fracture plan arc do not seem to be covered by suspension of fracking or addressed at all. Is this assertion correct?

    Also, are the BGS and Cuadrilla to release more accurate locations of the seismic epicentres for attempts at correlation with the geological faulting by the wider geological ?

    • Likening the waste water from a shower to that from an hydraulic frack is on similar lines to likening an intensity level 6 earthquake to dropping a shopping bag on the floor. But I suppose that if you work in an industry where you are exposed to radioactivity the comparison just might be more valid.

      • Thank you. I briefly read both papers and found the latter more useful. Interesting that it appears that the induced seismic events at PNR are amongst the studied/world highest induced by hydraulic fracking and comparatively rare.
        But there at first glance no reference to seismic events that then induce further events on other faults.
        The hydraulic fracture plan of well 2 does however mention geo mechanical linkage, so they are clearly aware of the potential…

  4. Who was “likening”??

    Waste water from showers is treated, waste water from farms is treated, waste water from motorways is treated, waste water from most other industry is treated. The difference is that the treatment required varies according to the level and nature of the contamination.

  5. Bl00DY Nutters!
    Extinction Rebellion protester from Aberdeen, Molly McLachlan, said the event had been targeted because “one of primary industries to blame for the climate devastation we’re facing right now is the fossil fuel industry”.

    She added: “We need to move forward with the energy transition and it’s not happening fast enough and we need to stop oil and gas extraction before we reach a point of no return.” But she is commenting on a report which was published at the end of last year? Not fast enough!, how fast does she think industry’s act!

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