The good news about Sudbury’s earthquakes
Rock engineer David Brown talks to CTV Northern Ontario's Callam Rodya about Sudbury's two recent earthquakes.
Published Friday, February 8, 2019 4:02PM EST
Last Updated Friday, February 8, 2019 6:13PM EST
It wasn't a dream, the ground underneath the Sudbury area has been shaking.
Two quakes in two days, the latest one measuring as high as 3.6 on the Richter scale, enough to rattle windows and nerves, but not much more.
David Wood is a rock engineer.
"It's something to be cognisant of, but not scared of." said Wood.
And he should know.
He's an expert in the mechanics of rock and knows exactly what's triggering these tremors.
"Only a handful are natural earthquakes. Almost all of them are either mining induced, blasting induced, or microseismic activity that occurs within the mine itself." said Wood.
In this case, it's the mining giant Vale that is shaking things up.
The company confirms to CTV News that two underground blasts, Wednesday afternoon at Garson Mine and early Friday morning at Creighton Mine, are what triggered the quakes.
In an email, Vale says it"takes many measures and precautions to try to minimize the impacts felt by the community as a result of our blasts and to do what we can to prevent seismicity."
But that seismicity was felt, and residents are understandably alarmed.
However, Vale says at no time was the public at risk, and they're probably right.
In fact, company blasting may actually be preventing stronger and more dangerous natural earthquakes.
Wood says mines will deliberately upset the underground to relieve the natural stresses.
"The more of this that happens, the more relaxed the ground is. So, the less able it is to build up the stress and hold the stress.” said Wood.
He confirms that theoretically, these smaller ones that we're feeling could be preventing a larger one from occurring.
It turns out; these earthquakes might be keeping us safe, even if they don't feel that way.
Michael Kolaj is a seismic analyst for Natural Resources Canada.
He provided this statement to CTV News:
"Natural Resources Canada detected two seismic events this week that were large enough to be felt in the Sudbury region. There was a M2.9 event (February 6th 5:08pm) at Garson and a M3.6 (February 8th 2:23am) at Creighton. The events were confirmed to have occurred in the mines by the mining operators. The M3.6 was more widely and strongly felt due to its larger size; a magnitude 3.6 event is roughly 5 times larger than a magnitude 2.9 event. Mining related seismic events are frequently recorded on seismographs in Sudbury, but they are typically small and cannot be felt outside of the mine. Typically there are about 1-3 events per year which are more widely felt. Both of these events were felt locally and felt reports were submitted to the earthquakes Canada website. Descriptions of these events match what we would expect for small events at close distances (e.g., weak to light shaking)."