Earthquakes in Canada
Earthquakes occur daily across Canada. On average, more than 4,000 earthquakes are recorded in Canada each year, according to the Geological Survey of Canada, of which about 50 are generally felt. British Columbia is the province that is most likely to experience earthquakes and this activity drops off considerably as you move inland from the coast.
An earthquake can happen naturally when rocks break and slip along a fault in the earth. However, human activity can also cause or “induce” seismic events or earthquakes. Man-made earthquakes always occur closer to the site of the activity, according to Natural Resources Canada.
Induced seismicity can result from a variety of industrial processes, including mining, construction, waste disposal, geothermal energy extraction and dam building (reservoir impoundment). These processes create tremors within the earth’s crust that can be measured and, at times, felt on the surface. Read more about induced seismic activity.
Emerging evidence indicates minor seismic activity can be linked to hydraulic fracturing, which is the process used to extract natural gas from deep shale rock formations that are typically 2,000 to 3,000 metres below the earth’s surface. The scientific evidence indicates that seismic activity resulting from hydraulic fracturing causes no injury or property damage, and does not pose a risk to public safety or the environment. Read the British Columbia Oil and Gas Commission report on induced seismic activity.
How can hydraulic fracturing cause seismic activity?
Hydraulic fracturing is a controlled process that injects pressurized fluids to the geological formations where natural gas is locked in dense rock, such as shale. The pressurized fluid is injected into deep shale rock formations and cracks the rock in order to release the natural gas trapped within the rocks. The energy released in this process can cause seismic activity. It is rarely felt on the surface and usually happens where the rock is being fractured, or 2,000 to 3,000 metres below ground.
What's the risk?
The Canadian data from the British Columbia Oil and Gas Commission (OGC) report focuses exclusively on the Horn River Basin in northeastern B.C. It points out that none of the seismic events associated with hydraulic fracturing have caused any injury, property damage or posed any risk to public safety or the environment. The largest seismic events in the OGC report are described as “minor”.
Managing the risk
Three initiatives have been undertaken to manage any risks:
- Canada’s natural gas producers are working with the OGC as the recommendations in the report are put into practice.
- Members of the Canadian Association of Petroleum Producers (CAPP) are finalizing a set of guidelines that outline procedures to understand, monitor, mitigate and avoid any negative effects of induced seismicity associated with hydraulic fracturing. These guidelines will complement other internal industry principles and practices related to water use, water quality, well bore construction and frac fluid disclosure. Details will be announced in the coming weeks.
- Upgrades to the seismic detection grid in northeastern B.C. to gain a better understanding of induced seismic activity associated with hydraulic fracturing in the unique geography of the Horn River basin.
Yy_rvPuvdwwWatch "Footage from Encana's Horn River play" on YouTube