Saturday 17 December 2011

Earthquakes near Blackpool

So, we've established that fracking won't cause volcanoes. But what about earthquakes? It's well known now that fracking activities appear to have produced two earthquakes at the Cuadrilla site near Blackpool. These earthquakes - in April and May 2011 - had magnitudes of 1.7 and 2.5. Earthquakes of this size have never been experienced during fracking before, so it's really interesting to have a look at them.

Firstly, how do their magnitudes correspond to what has gone before, and what earthquakes are like in nature. All fracking produces 'microearthquakes' - these are just like earthquakes except, as you'd guess from the name, much smaller. Typical earthquakes during fracking have magnitudes of -3 to 0. These are too small to be felt at the surface, even by a seismogram. However, geophysicists like myself will place geophones down boreholes near to the fracture stimulation to detect these microearthquakes, and use their locations to map the course of the fracture as it propagates out from the well. Earthquake magnitudes are on a logarithmic scale, so a magnitude -3 event releases 10^11 Dcm (that's dyne-cm, don't ask) of energy. A mag 0 releases 10^16 Dcm, so that's 10^5, or 100000 times larger. A mag 3 event releases 10^20 Dcm, so 10000 times larger than the largest event seen during fracking so far.

Why did this event happen then? Well, the official report claims that a critically stressed fault, near to the fracking site, was reactivated. As the fluid from the frack impinges on the fault, it increases the pore pressure, reducing effective normal stress and triggering failure. Seems plausible enough to me. A pre-existing fault is pretty much required to get a mag 3 quake. If the fault was close to critical stress, it implies this earthquake would have happened soon anyway - the fracking didn't produce a new earthquake, it just hurried it along.

A magnitude 3 earthquake is classed and 'small', and not damaging. If we lived somewhere like California or Japan, a mag 3 wouldn't even be noticed. It once you get up to mag 5 or 6, 1000s of times larger again than a mag 3, that people need to start really worrying. We have about 1 or 2 mag 3 events occurring naturally in this country every year. It'd feel something like a large truck going past your house at speed, rattling the window frames and such, but no damage caused.

So what does this mean going forward? Is a mag 3 quake worth stopping fracking and shale gas exploration for? Unfortunately, this is where scientists provide the facts (see above) and then hand over to the policy makers. The current system put in place by Cuadrilla is that if they trigger anything above a mag 1.7 they'll stop fracking and drain down the pressures. So it remains to be seen if they'll trigger more earthquakes in future wells. The report seems pretty confident that they won't, but then they would say that wouldn't they. They say it's an unfortunate accident of unique geology. However, the Bowland shale is pretty deformed and faulted, so it'll be really interesting to see if they can miss all the faults in the future.

Friday 16 December 2011

Letter to the Editor.....

The recent reports about fracking producing a volcano in the Mendips riled me enough to write an angry letter to the Wells Journal and Bath Chronicle. Still waiting to hear if either will publish it.

Dear Editors,

I am writing to express my concern at reports suggesting that shale gas exploitation could trigger a volcano in the Mendips (More concern over fracking, Bath Chronicle, Thurs 1st December; 'We could be sitting on a Mendip volcano' says Somerset expert, Wells Journal, Sat 3rd December). Such alarmist scare stories, with no factual basis whatsoever, will not help to promote a constructive discussion about shale gas exploitation as hydraulic fracturing develops in the UK.

Let us be clear, there is no 'river of lava ready to erupt' below the Mendips, no 'sleeping giant' to be awakened. The volcanic deposits in the Mendips were formed during the Silurian Period, approximately 425 million years ago. At this time, Britain was located 20 degrees south of the Equator, as the continental plates of Avalonia, Baltica and Laurentia collided to form an Alpine-scale orogeny. These volcanos ceased to be active, and rocks ceased to be molten, some 400 million years ago. All that remains are the solidified volcanic rocks, which contain a little residual warmth that heats the warm springs. Such deposits are common across much of the UK, in the Lake District, North Wales, and Western Scotland, for example.

There is a genuine discussion that needs to take place regarding shale gas and fracking. Potential issues include increases in heavy vehicular traffic moving equipment to the drill pads; the presence of 5 acre drill-pads, in place for perhaps 6-8 months or more in an area of natural beauty; the significant volumes of water required for fracking (usually measured in millions of gallons); and the ability of treatment facilities to handle and treat this water after fracking has been completed.

This discussion needs to be based on facts, logic and reason, weighing the potential economic benefits (particularly relevant in this time of austerity and high unemployment) against potential negative effects. Misleading scare stories about volcanic 'sleeping giants', or the videos of flammable tap-water that existed long before fracking began, are not productive. Besides slanting the discussion against shale gas exploration in an unfair manner, these reports in fact do a disservice to those who oppose shale gas on more reasonable grounds, as the temptation is then to lump all 'anti-frackers' together as unscientific, uninformed scare-mongers with no interest in evidence and no understanding of simple geological principles.

It is particularly concerning that this report comes from a Mendips District Councillor. One expects a certain degree on local knowledge from local councillors. However, despite his concerns about volcanic activity, Cllr Taylor seems totally unaware of the presence of one of the world's leading volcanology research groups (led by Prof Steve Sparks FRS CBE) just up the road at Bristol
University. I have had the pleasure of meeting Cllr Taylor during filming of the recent BBC Inside Out West report on fracking, and I have made the above points to him. However, the councillor appears to be less interested in gathering evidence than he is in promulgating baseless scare stories. The Mendips deserve better from their councillors.

I am not an advocate for the fracking industry. However, as a scientist I am concerned that, whatever the decisions made by Somerset Council (and at higher levels) on shale gas development, they should come from a careful assesment of the potential benefits and issues, based on evidence and reason. Unsubstantiated reports about 'rivers of lava' and 'sleeping giants' are of no help to this decision-making process, and it is of particular concern when these stories emerge from those elected to lead us.

Yours Faithfully,

Disgusted from Tunbridge Wells, etc etc

Sunday 4 December 2011

Could fracking cause a volcano?

Could hydraulic fracturing and shale gas extraction awaken a dormant volcano in the Mendips?

'We could be sitting on a Mendip volcano' says Somerset expert

Well, could it?

No. Not even remotely. The Moon's Hill quarry may well be the site of a Silurian volcano. However, the Silurian was 430 million years ago. At this period in geologic time, Britain was sitting somewhere near the equator, during a collision between two continental plates (Laurentia and Baltica), forming an Alpine-scale mountain building event. This 'volcano' has not been active for hundreds of millions of years. There are no longer two large continental plates crashing together (the kind of thing needed to get large volcanoes and earthquakes, see 'Pacific ring of fire'). There is no molten magma sitting just beneath the Mendips, ready to erupt. It would have cooled off 400 million years ago. There's just some slightly warm rocks capable of warming rainwater a little. Much like under large parts of the rest of the UK.

But what really grates me about this article is that I had a long chat Councillor Nigel Taylor while filming for a recent BBC Inside Out West special on fracking (go to about 11 minutes in). He put this concern to me (it didn't make the final cut for the IOW report), and I had a good long chat about what it means when a geologist talks about volcanic deposits from the Silurian, and that it doesn't mean there's still a volcano waiting to erupt just below the surface.

So it would appear that Cllr Taylor has chosen not to listen to clear science from a geologist, and has instead chosen to make himself appear to be a bit of berk (to anyone who understands geology at any rate). During our conversation, he appear to accept that he was wrong to be concerned about a volcano in the Mendips.

This is a disappointment, because this warning (and remember the headline claims this to have come from an 'expert') is no doubt making its way around the interweb as we speak, to be brought up at the next fracking protest. There are genuine reasons for concern about hydraulic fracking. If, however, rather than talking about the genuine issues, using facts, logic and science as our basis, we are instead talking about creating volcanoes, then everyone is wasting their time.

Nigel Taylor, you are deliberately and knowingly spreading misinformation about fracking. The Mendip district deserves better from their councillors. Regardless of the decision at which Somerset council arrives regarding fracking, please let it be based on fact, science and evidence. When scientific experts are available to you, please listen to them, don't play along and then ignore them.

Final rant, now aimed at 'This is Somerset': why do you name Cllr Taylor as an 'expert'? An expert on what? Not geology or volcanology, that's for sure. An expert on Somerset I guess would be the most literal interpretation, and perhaps he is. But then, if we're going to be talking about setting off volcanoes, surely the expert in question should be a volcanologist. And it's not like they're hard to find - just up the road in Bristol you could have found for example, Steve Sparks, one of the most pre-eminent volcanologists in the world. Had you wanted a little balance in your article.....