Ontario town rattled by 'mining-related' earthquake
Friday, December 14, 2018, 4:49 PM - It wasn't a particularly strong quake, but it didn't need to be for Kirkland Lake residents to feel the tremor on Wednesday night -- it happened right underneath their feet.
According to Earthquakes Canada, the magnitude 3.2 earthquake was centred almost directly under the city, 2 km west-southwest of town, at a depth of 1.5 km. More than 100 people reported to Natural Resources Canada that they felt the quake, which struck at 11:16 EST Wednesday night. Weather Network viewers reported hearing a "loud blast that shook a lot of homes" at the time the quake was recorded.
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Earthquakes Canada lists the tremor as 'mining-related', although no confirmation has been released. Local resident Jeff Wilkinson told CTV News he was concerned it might have been a fracture related to mining. "As you may know," Wilkinson told CTV, "we have had some fatal rockbursts in this area, so we're all sort of wondering whether it has happened again." A rock burst is a sudden, sometimes explosive, fracture that can happen in deep mines. The rock surrounding a mine shaft is under tremendous pressure from the rock surrounding it; sometimes this pressure can cause the rock surrounding the shaft to give way.
The location of the earthquake. Image courtesy Earthquakes Canada.
DOES MINING CAUSE EARTHQUAKES, OR IS IT THE OTHER WAY AROUND?
There has definitely been a lot of coverage of fracking-related earthquakes in recent years, as geologists point to the oil-extraction process for the rising number of quakes in places like Ohio and Oklahoma. Earthquakes related to mineral mining are a slightly different animal, however.
As happens with rock bursts, since mining leaves empty spaces that change the balance of pressure on the surrounding rocks, it's not unusually to get minor earthquakes related to the collapse of excavated regions. The excavation process itself can also result in events that register on the seismometer. According to a report from the Canadian Hazards Information Service, "Literally hundreds of [mining-induced activity] blasts are recorded and identified by the project on a yearly basis."
Sometimes it's a case of 'the chicken and the egg', however.
A lot of the minerals that people mine for are actually largely found along fault lines -- gold being among them. As Daniel Jaska, of the Geoscience Australia Earthquake Alert Centre, put it talking to ABC, "we have mining because of earthquakes."
"[Minerals like gold] are [along faults] because when and earthquake occurs, there is generally a flow of water or liquid that interacts with the rocks," said Jaska, "and over many millions of years forms minerals."
While seismic activity in central Canada tends to be fairly low, thanks to a lake of tectonic plate interactions in the area, there are 'weak zones' within plates that are subject to shifting when stress builds up in the interior of a plate, thanks to constant pushing at its edges.
Recorded earthquakes and earthquake zones in eastern Canada. Note that some seismic activity related to mining activity may be omitted from this image. Image courtesy Earthquakes Canada.