Weekend blast in Yellowknife registered as microearthquake

The planned blast that startled many Yellowknife residents on Saturday registered on seismic sensors as 1.4 magnitude on the Richter scale.

Planned blast at NWT Construction quarry measured 1.4 magnitude microearthquake

Saturday's planned blast in Yellowknife registered on seismic sensors as 1.4 magnitude on the Richter scale, the same size as a micro-earthquake. (Submitted by Jen Hayward )

The blast that shook and rattled many Yellowknife residents on Saturday was the size of a microearthquake, according to a seismologist.

Taimi Mulder is an earthquake seismologist with the Geological Survey of Canada, part of Natural Resources Canada. She said the explosion — which took place at 3:57 p.m. at NWT Construction Ltd.'s quarry — registered a magnitude of 1.4 on nearby seismic sensors.

Mulder said it's very common for blasts to be picked up by sensors and she's seen some in southeastern B.C. and southern Alberta register as high as a magnitude of 3.5.

"This was a very small blast," she said. "It's just because it was so close to Yellowknife that people felt it."

You could kind of feel it in your chest cavity, you know, it sort of reverberated.- Adrian Bell, City Councillor

Mulder explained that when a blast or earthquake happens, it sends out seismic waves, which are essentially like sound waves. People would've been able to feel a blast of this size up to 20 kilometres away, she said.

Mulder said 1.4 magnitude is comparable to a microearthquake and is "nothing to be concerned about."

With Canadian building code regulations, she said a blast or earthquake would need to register up to magnitude five before damage occurs. 

"They're nothing to worry about. You feel them, they're a little bit exciting, they might potentially wake you up in the middle of the night, but they're not large enough to do damage," she said.

'Quite scary,' says paddler

Many people across the city reported feeling the blast including Jessie Teed who was paddling on Great Slave Lake's Back Bay at the time. She said it was "quite scary" and the force of the blast caused the water to ripple.

"All of the birds in the area of the blast flew into the sky," she said. "A lot of birds in the Back Bay area also flew into the sky and into the opposite direction of the blast." 

While the city said the blast followed proper procedures, including sounding a sequence of horns, Teed said she didn't hear any horns before or after the blast. 

City Coun. Adrian Bell also felt the blast. He was at his home near Niven Lake at the time.

Among those that felt the blast was city councillor Adrian Bell. (submitted)

He said while blasting in Yellowknife is something he's used to, this one was a shock.

"I immediately knew what it was but just the energy behind it was quite surprising. It's not something that I've been used to," he said.

"You could kind of feel it in your chest cavity, you know, it sort of reverberated. So you could tell that it was a pretty big blast."

Bell said he has some questions about the size of blasts that have occurred and if the city should be looking more closely at safety and best practices.

While he noted he's not an expert on the subject he said if there is a way to alert more people about blasting beforehand it would "be wise to do so."

With files from Randi Beers


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