Nunatsiaq Online
NEWS: Nunavut January 18, 2017 - 7:00 am

Shake it up: a look at Nunavut’s earthquake history

"An event of this size, magnitude 5.9, happens on average once every 300 years”

STEVE DUCHARME
A Natural Resources Canada map showing the location of the Jan. 8 earthquake near Resolute.
A Natural Resources Canada map showing the location of the Jan. 8 earthquake near Resolute.
A screen grab map from a 3-D image of Frobisher Bay that shows arrows pointing to locations of suspected underwater landslides. (PHOTO COURTESY OF THE GEOLOGICAL SURVEY OF CANADA)
A screen grab map from a 3-D image of Frobisher Bay that shows arrows pointing to locations of suspected underwater landslides. (PHOTO COURTESY OF THE GEOLOGICAL SURVEY OF CANADA)

If you live in the High Arctic and worry about a repeat of the 5.9 magnitude earthquake that interrupted your dinnertime Jan. 8, don’t fret—the last one was a long time ago and a similar earthquake isn’t likely to happen again in your lifetime.

Nicholas Ackerley, a seismologist at Natural Resources Canada, said the latest event in the Barrow Strait near Cornwallis Island, which has so far produced about 10 smaller aftershocks since the original Jan. 8 earthquake, was “fairly rare” and remarkable enough to warrant close study.

“Our current model of Somerset and Cornwallis islands where this event happened says an event of this size, magnitude 5.9, happens on average once every 300 years,” Ackerley told Nunatsiaq News from Ottawa Jan. 12.

Of course, that’s just an average—so you shouldn’t start packing supplies for your descendants in 2317.

The return of a 5.9 magnitude quake to the same location, about 80 kilometres from the nearest settlement, isn’t likely to cause much damage, Ackerley said.

So, the latest earthquake was notable, but where does it stand in Nunavut’s seismic record?

Geologically, Nunavut is one of the oldest regions on the planet, going back billions of years, but is relatively quiet seismically with no active fault lines.

Instead, seismic events here are described as “intraplate,” or occurring within the same tectonic plate, Ackerley said.

Much of Nunavut’s seismic activity is directly linked to what scientists dub “post-glacial rebound,” which takes place as the earth slowly shifts and rises from the loss of weight from melted glaciers.

Unlike more tumultuous, “interplate” regions, such as the infamous “Ring of Fire” fault lines surrounding the Pacific Ocean, Nunavut is comparatively peaceful.

In fact, you need to go back more 80 years in NRCAN records before you can find an earthquake in Nunavut that approached a dangerous magnitude—and even then no fatalities were recorded due to its location.

A 7.3 magnitude earthquake struck Nov. 20, 1933, roughly half an hour before midnight, about 250 km east of Pond Inlet in the depths of Baffin Bay.

The event, the largest earthquake on record within Canada’s Arctic Circle, is included in NRCAN’s publication of “Significant Canadian Earthquakes of the Period 1600-2006.”

Outside Nunavut, in 1989, a 6.3 magnitude earthquake shook apart an ancient fault zone in Nunavik’s Ungava peninsula, draining one lake and creating another.

But that’s not to say that list of earthquakes is definitive. Ackerley said: Although Nunavut records extend back to 1933, these can be spotty in the early years.

It’s not until the records reach 1960 that the records become truly comprehensive, but, as it stands, according to those records, there have been about 2,000 seismic events logged in Nunavut. Most of these have been minor.

Further back in time, you have to rely on other sources. In some cases, these record the effect, but not the cause.

According to Nunavut historian Kenn Harper, at least one other recorded instance of a possible seismic event predates NRCAN’s catalogue, written about by a missionary named Reverend Peck and known as “Uqammmak” to Inuit.

Peck’s journal says a tidal wave struck Blacklead Island in Cumberland Sound, near Pangnirtung, on Oct. 20, 1903. Several Inuit families living near the island’s shore were affected when the wave descended on their homes and forced them to flee.

Large waves, which can also occur in Nunavut, are often associated with seismic events.

But, according to Ackerley, a magnitude 7 earthquake, such as the one recorded in 1933, is “barely big enough” to cause a tsunami, or tidal wave—and, according to records, the 1933 quake produced no such event.

For reference, to cause a tsunami of the scope seen in the 2004 disaster in Sumatra, an earthquake must be violent enough to lower huge swaths of the seafloor, displacing enough water to create the wave.

But that’s unlikely in a region such as Nunavut where there are no active fault lines that could potentially split the seabed, according to Ackerley.

Instead, the source for Nunavut’s historic tidal events might be less direct.

Ackerley said large earthquakes are not the sole cause of tidal waves. These can also be created by large glacial chunks falling into the sea, or landslides on the ocean floor.

The silt and clay-based seabed can be prone to landslide, either by reaching critical mass or being displaced by a smaller earthquake more likely to happen in Nunavut.

Several current projects within Nunavut involve mapping the seabed with 3-D imaging, Ackerley said, and have recorded signs of these underwater landslides.

The Geological Survey of Canada has also noted several signs of minor seafloor landslides in Frobisher Bay last March as its team compiled a digital map of the bay ahead of the construction of Iqaluit’s first deep sea port.

While no one today will be around to prove NRCAN’s 300-year average for the next Resolute earthquake, it’s the collection of data that’s important, Ackerley said.

“There is a ‘message in a bottle’ aspect to seismology,” he said. “But that’s how knowledge grows.”

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