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Earthquakes and fracking
Concerns over possible links between fracking and earthquakes originated in a report prepared for the European Parliament of June 2011. The evidence is several.
In particular, two tremors of 1.4 and 2.3 magnitude on the Richter Scale near Blackpool, UK, spurred the fracking company, Cuadrilla Resources, to commission a report into these events, published in November 2011.
This report caused concern that fracking fluid can lubricate fault planes and set off earthquakes. The findings need to be interpreted carefully. Slippage between rock strata did occur, setting off a ground vibration of the same order as that of a bus driving past. This low level of seismic activity cannot be linked to the gigantic forces of nature normally associated with earthquakes.
Straterra's press release on the earthquake issue has appended to it an independent opinion from GNS Science that New Zealanders need have no concern over low-level ground vibrations, or seismic activity, caused during fracking.
To put the issue into context, flooding river valleys for hydro dams, geothermal development, injection of waste water into underground reservoirs, and pile driving activity in bridge construction, can all cause "earthquakes" or seismic activity. Society has no concerns over these activities.
That is not to downplay the risks of fracking. There is no room for complacency, as GNS Science rightly states. Straterra agrees there should be monitoring to ensure that no dangerous ground shaking occurs as a result of fracking.
Fracking in context
"A passing truck generates as much if not more vibration – so the effects of seismic activity that are typically induced by hydraulic fracturing would be hard to separate from the background level of seismicity," - Dr Rosemary Quinn, GNS Science, puts the link between fracking and earthquakes into context.
Scientific American magazine places into context an upsurge in earthquake activity in Oklahoma State - it is unlikely to have anything to do with fracking.
In light of recent concerns over the links between earthquakes in fracking, in Taranaki, GNS Science produced a report in February 2012. It says a normal damaging earthquake starts at a depth of at least 5–10km, and is caused by a fault slipping by tens of cm or more across a distance of several kms, minimum. That would cause an earthquake of magnitude 4-5 or more (which would be at least 1000 to 30,000 times more energetic than occurs with fracking). In fracking, any fault slip, where there are faults, is no more than a few millimetres, across a distance of a few metres to perhaps 100m. Energy released from any such earthquakes would dissipate over short distances, with no effect at the depth where damaging earthquakes are generated. Based on overseas examples, the maximum seismic event that could be credibly envisaged in Taranaki due to fracking would be one of magnitude 2.