Terri-Jane Yuzda

The Earth Really is Moving Under Our Feet

Honorary Address Speaker Has a Lifelong Passion For Earthquakes – and He Feeds it Every Day

Freelance Writer

Remember the line from the Carole King song reminding us what it’s like to “feel the earth move” under our feet? It’s hard to forget these words as you listen to Garry Rogers talk about his lifelong passion — earthquakes.

No one can tell exactly where or when earthquakes will occur. The earth under our feet is not really as firm and stable as it appears: it is constantly moving. But if anyone can predict the next earthquake, it’s Dr. Rogers, an earthquake seismologist with the Geological Survey of Canada and head of the National Earthquake Hazards Program for Western Canada.

At his GSC office in Sidney, B.C., Dr. Rogers keeps a close watch on earthquakes across Western Canada. Each day he and his team of analysts meticulously sort through data from a network of seismographs and monitoring instruments across the country.

“We go through what’s happened in the last 24 hours, sort out the seismic ‘noise,’ save data for analysis and locate the earthquakes that have happened in Western Canada,” says Dr. Rogers, who was a guest speaker at the Honorary Address in Calgary in October. “If the earthquake is big enough, we calculate the faulting and stress mechanisms that caused the event.”

Each year the team locates and records about 1,500 earthquakes across the region.

“One of the most recent earthquakes occurred at about 8:42 p.m. on Oct. 11 just east of Victoria,” says Dr. Rogers. “It was a magnitude of 2.6 — so a fairly small earthquake — but a lot of people felt it across the greater Victoria area. We received e-mails from about 100 people about this quake.”

Plenty of Public Contact

Each year the team also fields hundreds of calls from the public, often from residents reporting tremors in their homes and buildings.

“In November 2002, for example, we received many calls from people across Western Canada reporting they felt a large earthquake. The earthquake actually occurred more than a 1,000 kilometres away in Alaska, but it was such a large event — magnitude 7.9 — that it caused buildings in Edmonton, Calgary, Vancouver and Victoria to gently sway back and forth.”

An earthquake measuring between two and three on the Richter scale is the lowest normally felt by people. And because many of the earthquakes in Western Canada measure between 1 and 2, we hardly notice them. But as Dr. Rogers warns, there’s always the potential of larger earthquakes, especially on the West Coast.

The area just west of Vancouver is considered one of the most vulnerable in the country. It’s here in the Juan de Fuca Strait that two tectonic plates — the North American Plate and the Juan de Fuca Plate — rub against each other. The North American Plate is gradually sliding underneath its neighbour. And as it does, pressures build along the plate boundary.

Eventually, scientists say, this will unleash a “subduction earthquake” – an incredibly powerful quake that can measure nine on the Richter scale.

Dr. Rogers says the Geological Survey of Canada has found evidence of a large subduction earthquake that destroyed an Aboriginal village near Victoria more than 300 years ago.

In their oral traditions, First Nations people on the island talk about a big earthquake that occurred in the winter in the middle of the night. The earthquake probably began just offshore, and then minutes later the water of the bay rose into a tsunami, a massive surge of water several metres high, that pushed its way ashore, tearing trees from the ground and pounding wooden buildings to pieces.

Thanks to Japanese records from that time that describe a tsunami damaging that country’s east cost, it’s possible to date the earthquake to around 9 p.m. on Jan. 26, 1700. By examining trees submerged centuries ago in a peaty bog, scientists have also been able to count tree rings back to this destructive event.

Could such a killer quake happen again?

“Mother nature doesn’t go like clockwork. Sometimes we’ve had two or three major earthquakes in a year on the coast. The last one was in 1946,” Dr. Roger says, referring to a 7.3 quake that damaged school buildings near Courtenay, Vancouver Island. “Since then, there’s been an absence of big earthquakes on the coast.”

The Next Big One

Hunting for ways to anticipate the “next big one” has become a quest for Dr. Rogers. Last year he came closer to this goal, as he and his colleague, Herb Dragert, announced a scientific breakthrough.

By studying narrow frequency bands from seismographs, the two scientists have discovered a way to “listen” to tectonic plates slipping under Vancouver Island.

“We’ve found that about every 14 months the Juan de Fuca and North American plates put out pulsating vibrations that signal they are going to slip against each other. These stresses are building up in the earth like a staircase.

“Every time this happens we’re moving up the staircase to the next big one. We don’t know exactly where we are in the staircase. But this gives us an important clue.”

Should we be concerned about a serious earthquake in Western Canada? And how well prepared are we?

This is a question that is top of mind for Dr. Rogers, who, as a member of the Canadian National Committee on Earthquake Engineering, regularly meets with engineers and academics to review and recommend earthquake design requirements for Canada’s National Building Code.

“If engineers understand the ground-shaking forces of earthquakes, they can design structures that can successfully resist these events. To help them do that, we look at recent earthquake events from around the world to determine what structures fail — or don’t fail. If there are important lessons from these events, we incorporate these into the building code.”

After studying recent earthquakes in Japan and the U.S., the committee plans to introduce new, expanded earthquake design requirements in 2004.

“The new code will provide more information for designing earth-resistant structures of all sizes,” says Dr. Rogers. “Also, we’re incorporating changes for the first time to address ground-shaking from very large subduction earthquakes.”

The Real Impact

Indeed, earthquakes should not be underestimated. Dr. Roger says he never ceases to be impressed by their power.

“In 1989 there was a fairly large earthquake south of San Francisco. One of the hotels that I’ve stayed in was severely damaged, with big cracks going up it. When you see that impact in a building, where you’ve been and walked in, it makes it all very real.”

Dr. Roger’s fascination with earthquakes goes back to his days as a 10-year-old growing up in Vancouver. “As a kid, I was always really impressed by the world of big interesting geologic events – earthquakes, tsunamis and volcanoes,” says the 58-year-old scientist.

Today, after decades of study, his fascination continues to deepen.

“In the last decade especially, the whole field of earthquake science has really accelerated, with new computers, with better monitoring instruments. And this is encouraging because it means that someday we’ll get to the bottom of some of the fundamental forces that we don’t understand.

“ Like any scientist, I’m fascinated with how the earth works and want to contribute to that understanding. But I also get a double benefit, knowing that the results of my work are going to directly help make people safer — and for me, that’s very satisfying.”

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