A question of seismicity
A lot of drivel is pumped out about seismicity.
We are continually being told by Academics like Prof. Mike Stephenson at the BGS that we are foolish to be concerned about seismicity because the tremors are too weak to do any damage. If questioned they tend to qualify the statement by explaining that they mean damage to housing. We find this particularly frustrating as it appears that in saying this these academics are deliberately misrepresenting our concerns.
This happened again recently when Dr James Verdon was quoted in an article at http://www.inlec.com/blog/2013/09/fracking-is-this-the-future-of-uk-energy/
In this article he said of fracking induced earth tremors: “They are typically magnitude 2 – 3. This is large enough to be felt, but not large enough to cause damage of any kind.”
We took exception to this statement as it is blatantly untrue. We know that the Preese Hall earthquakes caused damage to the well casing. We asked him to explain himself on Twitter and he said “I think the context is clear – addressing concerns about seismicity in terms of damage to buildings/infrastructure at surface”
We pointed out that there was absolutely no reference to “buildings/infrastructure at surface” in his entire article and that the phrase “damage of any kind” was totally unambiguous.
Eventually he conceded that he was:
“Happy for Matt to edit “large enough to be felt, but not large enough to cause damage of any kind” to …”large enough to be felt by people at the surface, but not large enough to cause damage of any kind to buildings or infrastructure” if he feels so-inclined…
We felt this wasn’t quite enough as it totally ignored the damage that had been caused to the well casing so we pointed out that we had been offered the opportunity to put the case we were making if he didn’t correct it more fully. Dr Verdon declined to comment further.
So we wrote a brief paragraph or two explaining our concerns which can now be found at the bottom of that article. Here it is
Q: What evidence is there to suggest that earthquakes can be an effect of fracking?
A: “Here in the UK High Volume Hydraulic Fracturing has only been done only once – at Preese Hall near Blackpool in 2011. The fracking process caused about 50 minor seismic events, the two most powerful of which were a magnitude 2.3 tremor on April 1st and a Magnitude 1.5 tremor two months later on 27 May.
A report (https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/48330/5055-preese-hall-shale-gas-fracturing-review-and-recomm.pdf) into these seismic events was commissioned by the DECC .
Shortly after this report was released Professor Mike Stephenson of the British Gelogical Survey told the Shale Gas Environmental Summit that “the tremors were way to small to cause any damage”. This claim has also been repeated more than once by other leading academics. However, we learned from the report that, as well as the minor property and infrastructural damage reported anecdotally, the tremors had actually damaged the well casing. The casing was ovalised over several hundred feet, as can be clearly seen in the DECC report which even shows a diagram of the damage to well.
This damage happened because some of the fracking fluid migrated into a fault, which caused the fault to slip, and this led to the tremors”.
Q: Why are earthquakes a cause for concern?
A: “Just after Cuadrilla’s seismic survey was carried out in 2012, an engineer at a Cuadrilla roadshow was asked if the fault which caused the Preese Hall tremors had shown up on the survey. He said not yet, but they were awaiting the survey data to be fully processed. He said that they believed they knew where the fault was, from modelling, but added that it might be too small to show up in the survey results.
We don’t know yet whether Cuadrilla have found the location and extent of the particular fault concerned, or of any of the others in the area. The DECC report tells us though that “In the present state of knowledge it is entirely possible that there are critically stressed faults elsewhere in the basin. “
Professor Stephenson of the British Geological Survey said on BBC Radio 4′s Inside Science programme recently: ”What you have to be able to do when you decide you want to hydraulic fracture is make sure there are no faults in the area. That’s really very very important”. Here in West Lancashire which sits on top of a large section of the Bowland Shale, we already know we live in a faulted area. We also have two aquifers, one saline and one fresh which are separated by the Woodfold Fault.
The concern that local residents have is nothing to do with whether earthquakes will cause their houses to fall down. We know that this is highly unlikely. We are concerned that any seismic event has the potential to damage the well casings of one or more of the 4,000 wells which may be needed in our area. If the integrity of the wells were compromised then fracking fluids containing a variety of toxic and radioactive materials could escape and cause a major pollution event which might then threaten existing industries like tourism and agriculture, as well as our health.
It should be noted in this context that the seismic activity which concerns us is not solely caused by fracking. A magnitude 3.3 tremor which happened just of Blackpool in August being the latest example of locally occurring earthquakes which are not caused by fracking but which could still damage any well bores in their vicinity.
Faults are also a potential route for methane and fracking fluid to migrate to other strata of rock such as aquifers or to reach the surface. This is one of the reasons that fracking has been banned in France. A recent study by independent German academics echoed Professor Stephenson’s conclusions that fracking in fault zones must be banned.