A UK study into hydraulic fracking has found the process caused small earthquakes near Blackpool last year, however it will not cause damaging tremors.

The report, undertaken by independent experts and commissioned by the UK's Department of Energy and Climate Change, looked at the relationship between hydraulic fracking operations by the Cuadrilla company at Preese Hall well, near Blackpool in Lancashire, and small earthquakes between April and May last year - the largest a magnitude 2.3.

Test fracking by the company was stopped following the quakes.

Fracking - or hydraulic fracturing - is a mining system that involves injecting chemicals into rocks so they break, releasing oil and natural gas.


The report agreed with previous studies that the earthquakes were caused by the process, however concluded it was safe for fracking operations to resume.

It said the stress in the fault was pre-existing and the hydraulic changes made by hydrofracturing simply initiated the earthquake sequence. The earthquakes would likely have happened at a later date anyway.

"There have been no reports of structural damage from mining-induced earthquakes of this magnitude in the UK, so an event induced by a hydraulic fracture treatment at a greater depth is unlikely to cause structural damage," the report concluded.

"There are, however, examples of mining induced earthquakes of similar magnitudes in the UK that caused superficial damage, for example, minor cracks in plaster, though these occurred at shallower depths.

"Such an event would be strongly felt by people within a few kilometres from the epicenter and could cause some alarm."

The report recommended steps be taken by the industry to mitigate further seismic risks, such as a smaller pre-injection and monitoring stage for hydraulic fracturing procedures, real-time monitoring of the locations and magnitudes of seismic events and a "traffic light" control regime - with a red light warning at seismic activity levels magnitude 0.5 or above meaning fracking action should be stopped.

This is lower than the magnitude 1.7 threshold proposed by Cuadrilla's experts.

Professor Andrew Alpin of Newcastle University School of Civil Engineering and Geoscience welcomed the report, which he said gave "cautious support" to continued hydraulic fracking.

"We know already that hydraulic fracturing can cause small-scale earthquakes but this study, along with others in the US, shows that they are of insufficient magnitude and extent to cause structural damage or to allow gas or chemicals to leak into much shallower drinking water aquifers.

"I also note the strict protocols recommended to mitigate future seismic risk, which it would be wise to follow during these early stages of UK shale gas exploration."

University of Leeds professor of petroleum and geo-engineering Quentin Fisher said the recommendations seem sensible in the short term, but should be "reviewed as more data becomes available to ensure that they do not result in over-the-top regulations that unnecessarily restrict the development of shale gas plays within the UK".

"Overall, this report that adds to a large body of evidence indicating that hydraulic fracturing is a commonly used industrial practise that is very safe when conducted by responsible operators."

A report by the US Geological Survey last week said that increased seismic activity taking place in some areas of the United States was almost certainly the result of oil and gas drilling activities.

Christchurch City Council last week voted unanimously to declare the city a fracking-free zone.