Seismic activity
The areas where unconventional gas is extracted were noted to have increased seismic activity. These phenomena are usually micro shocks which do not exceed the amplitude of 3.0 on the Richter scale, which means that they are not felt by humans.
The connection between gas production from unconventional resources and the increasing number of seismic shocks is becoming noticeable and its source is yet to be explained.
According to the research conducted by the United States Geological Survey in 2012 in Central America, including Ohio and Arkansas, the number of seismic activities caused by man in previous years was much higher than before 2000. American scientists were unable to prove that the rapidly developing gas extraction from unconventional resources, especially the impact of gas production using the hydraulic fracturing process, had a direct impact on the increased seismic activity.
Seismic shocks which were linked to the extraction of gas from unconventional resources also occurred in the UK. In April and May 2011, near Blackpool, on the area owned by Caudrilla Resources there were noted two micro shocks with the magnitude of 2.3 and 1.5 on the Richter scale. A special report prepared by a group of experts commissioned by the company confirmed that the hydraulic fracturing process was the probable cause of the shocks and their occurrence was the result of the non-standard geological structure of the area. After this occurrence all work associated with shale gas extraction was halted until December 2012.
The seismic activity in Poland associated with gas extraction from unconventional resources was studied by the Polish Geological Institute. The measurements conducted from July 15 to September 30 2011 on the Łebień LE-2H borehole showed no seismic activity which could be associated with the process of hydraulic fracturing.