Seismic activity is rarely felt on the surface and usually occurs near where the rock is being fractured, or 2,000 to 3,000 metres below ground.
Seismic activity or earthquake activity, which is caused by human activity, is called induced seismicity. It is associated with several industrial processes, including geothermal energy extraction, mining, dam building, construction and hydraulic fracturing in natural gas development.
Earthquakes and hydraulic fracturing
The energy released by hydraulic fracturing (also known as fracking) causes rocks deep underground to crack, which by nature can cause seismic activity. Seismic activity is rarely felt on the surface and usually occurs near where the rock is being fractured, or 2,000 to 3,000 metres below ground.
Seismicity associated with hydraulic fracturing is usually recorded as microseismic events not felt on the surface because of their low magnitude. Of the seismic events felt on the surface, most range from 0 ML to 3.0 ML on the Richter scale. This is the equivalent of vibrations felt by a passing truck on the road. In rare cases, hydraulic fracturing has caused seismic events of 4.0ML to 4.8ML. Even at these levels, property damage or risk to public safety is unlikely.
Regulations for induced seismicity
In parts of British Columbia and Alberta, natural gas companies are required to monitor for seismic activity associated with hydraulic fracturing on their operating sites. Companies must also develop, and file with the regulator, a response plan in the event their operations trigger a seismic event. Any seismic event of 2.0 ML or greater must be reported to the regulator. In the rare case an event of magnitude 4.0 ML or greater occurs, hydraulic fracturing operations must immediately stop allowing for an investigation to be conducted by the regulator. Operations may only begin again once the regulator has given permission.