A spate of small earthquakes in B.C.'s remote northeastern corner were caused by a controversial technique used to extract natural gas from shale rock, a report by the province's energy regulator says.
The B.C. Oil and Gas Commission launched its investigation after a "number of anomalous, low-level seismic events" were detected in the Horn River Basin, a gas-rich shale formation that has attracted some of the industry's biggest players.
"The investigation has concluded that the events observed within remote and isolated areas of the Horn River Basin between 2009 and 2011 were caused by fluid injection during hydraulic fracturing in proximity to preexisting faults," the agency said in a recent report.
In order to break the rock and free the gas trapped inside it, operators inject a combination of water, sand and chemicals underground at high pressure.
The process known as hydraulic fracturing, or fracking, has drawn concern from environmentalists and landowners for the amount of water the process requires and for potential contamination of groundwater.
Studies have also linked fracking to earthquakes around shale formations in England and Oklahoma.
The 38 events detected by Natural Resources Canada ranged between magnitudes of 2.2 and 3.8 on the Richter scale.
A quake of between 4.0 and 4.9 is considered "light" and may cause a noticeable shaking of indoor items and rattling noises.
Another 234 events were picked up by industry-deployed devices in the area that are capable of picking up much smaller shakes than Natural Resources Canada's equipment can.
"We wanted to make sure that we knew what was causing the events, and we wanted to make sure that the events would pose no risk to safety or the environment," said Ken Paulson, chief operating officer at the commission.
Only one quake was felt at the surface near where the fracking was taking place.
"There was no risk posed to public safety or environment by any of the events that were looked at as part of this investigation," Paulson said.
The report said more than 8,000 fracking completions have been performed in northeastern B.C. that haven't been associated with unusual seismic activity.
The report said no quakes were recorded in the area prior to April 2009.
It said all of the events began after fracking took place. The quakes happened within five kilometres of fracking operations and within 300 metres of the depth at which the rock was being fractured.
Among other things, the report recommends improvements in seismic detection in the area, further study to identify pre-existing fault lines and stronger monitoring and reporting procedures.
It also calls for an examination of the relationship between hydraulic fracturing parameters and seismic activity. For instance, lower pump rates or injection volumes may be considered.
Geoscience B.C. is providing funding to update the seismographic grid network in the area to boost monitoring. The commission is also undertaking further study with the University of British Columbia.
The Canadian Association of Petroleum Producers welcomed the report's recommendations, acknowledging that seismic activity associated with oil and gas extraction is of concern to the public.