Canada’s little-known earthquake zones: Baffin and Nunavik

AARON SPITZER

IQALUIT — The ground buckled, the sea shuddered and a roar rumbled through the dark winter sky.

It was the most violent earthquake ever recorded in eastern Canada — a tremor as severe as those that recently caused carnage in India and El Salvador.

And it happened right here in Nunavut.

It was Nov. 20, 1933, when a monster earthquake ripped through the sea-floor of Baffin Bay, not far offshore from Pond Inlet.

Earthquake scientists — known as seismologists — believe its magnitude measured 7.3 on the Richter scale. A quake that powerful can hurl humans to the ground, shake buildings apart, set off landslides and trigger giant tidal waves.

Seismographic instruments around the world detected the earthquake’s effects.

But unlike the quake in India last month that killed an estimated 30,000 people, the Baffin Bay tremor isn’t known to have caused any damage or inflicted any injuries.

Quake-prone zones

While Nunavut’s “big one” may not have been a killer quake, it points to a little known fact: that Nunavut and Nunavik are among the most earthquake-prone zones in Canada.

According to data gathered by the Geological Survey of Canada, the northeast coast of Baffin Island and the High Arctic archipelago have a particularly high incidence of earthquakes.

On average, 40 quakes shake Nunavut each year. Most are minor — below magnitude 4.0. They may make a low rumbling noise, but they produce little perceptible shuddering of the ground.

Already in 2001 at least three tremors have been triggered in the territory, one of which — a gentle 2.8-magnitude shiver too subtle to be felt — originated a mere 120 kilometres southeast of Iqaluit.

Big quakes in the eastern Arctic aren’t unusual.

In 1989, on the Ungava Peninsula in Nunavik, a magnitude 6.3 earthquake tore open the tundra and shook up surrounding communities. The convulsing of the earth shattered stone, partially drained one lake, and created a new lake where none had been before.

That quake, according to scientists, was unusually shallow. Its epicentre was judged to be about three kilometres below the surface of the Earth, whereas most quakes begin 10 to 20 kilometres down.

Another violent quake — registering a magnitude of 6.1 — hit northern Baffin Island in 1963.

Predicting quakes impossible

The fact that such severe shake-ups happened here in the past suggests that more could strike at any time.

“It’s certainly indicative that there’s a potential for similar earthquakes,” said Maurice Lamontagne, a seismologist with the Geological Survey of Canada.

Lamontagne said it’s just a matter of luck — and low population density – that no known deaths or damages have resulted from Nunavut quakes.

“It’s a question of chance,” he said. “Up there the communities are so far apart that the chances are fairly small that when you get an earthquake it’s going to cause damage.”

Presently, there’s no way to predict earthquakes. But, said Lamontagne, they can be prepared for them.

Due to the frequency of tremors along the northeast coast of Baffin Island, the National Building Code states that new structures built in the region should meet the strictest requirements for stability and earthquake-resistance.

Even buildings erected elsewhere in the Baffin region and Nunavik are under tighter requirements than most other areas of Canada.

It also helps to know what to do if an earthquake strikes. Earthquake experts advise that if you’re indoors when a quake occurs, take cover under a desk, table, bed or door-frame. If you’re outdoors, stay away from anything that could collapse, such as houses or rocky outcrops.

The science behind the shaking

Scientists aren’t quite sure why the eastern Arctic shakes so much.

The vast majority of earthquakes — 97 percent — occur at the boundaries of continental, or tectonic, plates, where vast slabs of the Earth’s surface grind up against one another.

But Nunavut is situated well inside North America’s tectonic plate. Quakes here occur along internal faults, or weaknesses in the Earth’s crust. In many places, such faults contain little energy and don’t pack much punch. Often they display no seismic activity at all.

“But in certain areas you do get activity,” Lamontagne said. “Northern Baffin Island appears to be quite active.”

One theory about Far North earthquakes is that they result from the retreat of the glaciers that once covered most of the region.

As the enormous ice-sheets have melted away in recent centuries, the weight on the land has been removed and the ground is actually rising up. When certain areas ascend faster than others, the differential speeds causing tearing and grinding deep in the ground, triggering significant earthquakes.

Nunavummuit concerned about quakes can take heart: No one in Canada has ever been killed directly by an earthquake.

The most violent seismic event ever to shake Canada was a magnitude 8.1 mega-quake that hit the Queen Charlotte Islands of British Columbia in 1949.

In 1929 in Newfoundland, 27 people were drowned by a tidal wave set off by an earthquake of magnitude 7.2.

It is thought that the maximum possible magnitude of an earthquake is 9.5. Such a quake occurred in 1960 in Chile, resulting in the deaths of more than 2,000 people.