On 27/03/11 and 01/04/11 two, low magitude seismic events were recorded in Blackpool(http://www.bbc.co.uk/news/uk-england-lancashire-15550458). The Earthquakes, measuring only 1.5 and 2.3 on the Richter Scale respectively, occured in the vicinity of the Preese Hall fracking site run by Caudrilla Resources ( http://www.cuadrillaresources.com/).
The BGS installed temporary recording devices after the 1st earthquake and were subsequently able to locate to epicentre of the second just 500m from the site.
Here is a link to the BGS Blackpool map showing the epicentre localities: (http://earthquakes.bgs.ac.uk/research/earthquake_hazard_shale_gas.html).
The result of these very small magnitude of these anthropogenic earthquakes was a temporary suspension in fracking practices at the site. The company in charge, Caudrilla Resources, also commissioned independent studies into the complex relationship between the process of hydraulic fracturing and so called 'micro-seismicity' at their site. Caudrila claim that future earthquaes have a very low probability of repeat occurence however as explain in this paper, the answer is not so simple:(https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/48330/5055-preese-hall-shale-gas-fracturing-review-and-recomm.pdf).
To summarise, the study was unable to definitively locate the 'causative fault' and have made suggestions for further field data. This includes a 3D seismic survey to identify the underlying fracture pattern in the basin.
The most important aspect to take from this report is about 'Hazard Mitigation' and the importance of continuous, passive monitoring- i.e identification of a possible hazard before the event takes place. Take a look at this link to LandTech, a company which provide fracking-induced seismic monitering for large fracking companies ( http://www.landtechsa.com/default.aspx?c=030200)
Here is a useful (but very long!) link to a pdf on Micro-Seismicity:
(http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=6&ved=0CGgQFjAF&url=http%3A%2F%2Fwww.api.org%2F~%2Fmedia%2FFiles%2FPolicy%2FHydraulic_Fracturing%2FFacts-HF-and-Seismic-Activity.pdf&ei=vrNlUu6OA6K-0QWG-IHIAw&usg=AFQjCNHrrew-8A_U-nXBLFzLJhi4sNkBzQ&sig2=hmlzMut9_c5FQhh9DDeMOg&bvm=bv.55123115,d.d2k)
And a link to methods used to monitor Micro- Seismicity:
(http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=8&ved=0CHMQFjAH&url=http%3A%2F%2Fwww.cspg.org%2Fdocuments%2FConventions%2FArchives%2FAnnual%2F2011%2F255-What_Does_Microseismic_Tell_Us.pdf&ei=vrNlUu6OA6K-0QWG-IHIAw&usg=AFQjCNHXjO7I6X8SHfR6S65vztla8WOplg&sig2=q6GFfZynZDfl7zwFIUMC7A&bvm=bv.55123115,d.d2k)
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