August 22, 2019

expert reaction to the Lancashire fracking tremor

Tremors of 1.55 and 0.87 magnitude were recorded on the 21st and 22nd of August in Lancashire following fracking events at the Preston New Road site.

Dr Stephen Hicks, Research Associate, Faculty of Engineering, Department of Earth Science & Engineering, Imperial College London:

“Hydraulic fracturing (‘fracking’) involves injecting fluid in the ground to create many fractures a few kilometres deep in the ground. This fracturing is like how natural earthquakes occur – but at a much smaller scale – they generate tiny vibrations that can we record using sensitive instruments at the surface (called “seismometers”). The detection of many “micro-earthquakes” by the British Geological Survey in Lancashire over the past few days, are a testament to the high sensitivity of the seismic recording networks that have been installed by the British Geological Survey, UK universities, and the drilling operator. Data from these sensors is being analysed in real-time.

“The ground shaking produced by yesterday’s magnitude 1.6 induced earthquake would likely have only been felt by people living in the immediate epicentral area and under favourable conditions (e.g. by people at rest/sitting down). Since the earthquake magnitude scale is logarithmic, the magnitude 2.3 Blackpool earthquake induced by hydraulic fracturing back in 2011 released over 11 times more energy than this week’s 0.5 event.

“Yesterday’s magnitude 1.6 earthquake occurred in the evening, once fracking during the day had finished. This is called a “trailing event” and shows that the injection of fluids into the ground can redistribute stresses even long after fluid injection has stopped. Fracking operations will now be temporarily suspended according to current UK regulations.

“Larger earthquakes (magnitude greater than 2) that more people at the surface would feel with a stronger ground shaking intensity would need to occur on pre-existing geological weaknesses (called “faults”), which provide the area needed for larger rupture. We do not currently fully understand what causes small fracture events to cascade into a larger fault rupture, and we are not able to accurately map every small fault in the ground. We also do not fully understand why different areas of the world respond differently to fluid injection.

“Many fracking operations have occurred around the world without inducing earthquakes that people can feel at the surface. There are only a handful of examples of fracking causing larger (magnitude greater than 4) earthquakes.

“Research is ongoing as to whether such larger triggered earthquakes can be proactively forecast ahead of time which could be used for operational purposes, and might offer an advancement over the existing reactionary magnitude-based traffic-light regulation system.

“Time will tell as to whether fracking operations in Lancashire can produce economically sustainable levels of gas without causing earthquakes that are consistently felt at the surface. There are currently many uncertainties as to how the Bowland Shale will mechanically behave in response to large-scale fluid injection.”

Declared interests

None received