Blog

After the Chile quake, is ‘the big one’ around the corner for B.C.?

Around 8:45 p.m. Wednesday, residents on Chile’s coast were jolted from where they stood or sat when the earth began to shake violently. Items tumbled off shelves, landslides were triggered, power was knocked out to thousands, and several fires destroyed businesses. Though tragic, it was miraculous that only six people lost their lives in the magnitude-8.2 quake.

A similar situation — or worse — could lie in store for residents along the coast of British Columbia, though seismologists aren’t concerned about the Chilean earthquake being the catalyst to a major earthquake here at home.

“We don’t expect any impacts in B.C. in terms of triggering [an] earthquake,” John Cassidy, a seismologist with Earthquakes Canada told Global News. “Looking back at previous events over time, we don’t see any direct link between these very distant earthquakes triggering very large, very distant earthquakes.”

However, that doesn’t rule out smaller ones being triggered.

Cassidy explained that when large earthquakes — magnitude 8 or 9 — occur any place on Earth, it can trigger smaller earthquakes around the globe.

“The [seismic] waves from that earthquake will circle the globe,” he said. “And as those waves, sort of a rolling motion, pass through certain areas, they will trigger small earthquakes. So you’ll see micro-seismic, or very tiny earthquakes, that people don’t feel.”

Generally, the this type of repercussion is limited to volcanic areas, which also includes Yellowstone National Park. That area received a magnitude-4.8 earthquake on March 30. It was the strongest in the area since 1980.

“It’s an interesting phenomena that was discovered, but we don’t see these waves triggering large earthquakes,” Cassidy said. “But it’s a young science and we can’t say absolutely not, but our experience so far is that we’re not seeing large earthquakes being triggered by these waves.”

The Chilean earthquake is actually similar to the type of earthquakes B.C. receives, called subduction earthquakes. This occurs when a part of one tectonic plate slides beneath another.

“It’s a very important earthquake, in that we can learn from this earthquake, because we have exactly the same kind of earthquakes off of our coast.”

The plate that subducted, or moved beneath another plate, off the coast of Chile is called the Nazca Plate. The plate moves toward Chile about 6 cm a year. Off the coast of B.C., the Juan de Fuca plate moves in the same manner at 5 cm a year.

In the case of the Juan de Fuca plate, seismologists know that a large earthquake occurs roughly between 200 to 850 years apart. And by ‘big one,’ seismologists mean a magnitude-9. The last one was in 1700, which means that, statistically, B.C. could expect one.

“We’re right in that window, where certainly we should be prepared for one of those earthquakes.”
If such a major earthquake were to occur, the effects could be enormous. For one, the shaking would last for about four to five minutes. For those on the west coast of Vancouver Island, they would have less than an hour to make it to higher land before a major tsunami washed ashore. As well, parts of the west coast of the island could drop as much as a metre.

“You’d see damage. You’d see landslides and liquifaction effects through the lower mainland and certainly all across Vancouver Island,” Cassidy said.

Not only that, but places as far as Toronto could feel the shaking. People in highrises would feel their buildings sway as the shockwave reached the city.

Trying to predict earthquakes

The difficulty with earthquakes is that there is, for now, no way to predict them. Though “swarms” of quakes — a cluster of localized earthquakes — have been linked to predicting a bigger earthquake, it’s not an exact science.

“It’s something that certainly people will be looking at really carefully now, because that’s one of the big questions,” Cassidy said. “Before one these giant earthquakes, is there any indication, any signal, any change in land level, or in seismicity that might tell us that one of these giant earthquakes is about to occur?”

But looking back at earthquake history, these swarms predict a larger one only 1 out of 20 times. That means 19 out of 20, there is no major quake that follows, making it an imperfect way to forecast larger earthquakes.

The good news for B.C. residents is that the Chile earthquake isn’t a portent of disaster. But the big one could be around the corner.

Source: http://globalnews.ca/news/1246076/after-the-chile-earthquake-is-the-big-one-around-the-corner-for-b-c/

BC is not ready for a catastrophic earthquake: Auditor General

VANCOUVER (NEWS1130) – A major audit by BC’s Auditor General has found we are not ready in this province for a catastrophic earthquake.

The audit found that Emergency Management BC (EMBC), the organization tasked with preparing government’s response to such an event, is not adequately prepared.

The audit also found that neither the province nor EMBC has made preparing for a massive earthquake a priority.

Source: http://www.news1130.com/2014/03/25/bc-is-not-ready-for-a-catastrophic-earthquake-ag/

Opinion: B.C. started with schools and now must prepare other structures

Province needs to ensure all public buildings are earthquake ready – Ann English

British Columbians who live on the south coast can marvel at how lucky we are to call this place home. However, B.C.’s engineers and geoscientists understand — perhaps more acutely than most — that our extraordinary natural beauty is paired with the ever-present danger of a significant earthquake. And that makes living in paradise just a little more complicated.

The question is not if a significant earthquake will hit B.C. (since 1872, nine earthquakes greater than magnitude 6 have shaken our region, most recently near Haida Gwaii in 2012.), but when. The only question is when our luck runs out and such an earthquake occurs in a much more populated area. As the 6.3-magnitude earthquake that shook Christchurch, New Zealand, in 2011 demonstrated, when such an earthquake hits, significant damage ensues.

Given the inevitability of a damaging earthquake on B.C.’s south coast, our first responsibility is to protect the most vulnerable among us from harm. That’s why the Association of Professional Engineers and Geoscientists of British Columbia welcomes the consultation and public education campaign on earthquake preparedness and response recently announced by the B.C. government.

APEGBC already has deep experience in this area, as a result of our work with the B.C. government and the University of British Columbia to address seismic upgrades at B.C. schools. The B.C. School Seismic Mitigation Program is a tremendous success story; so much so, that the United States Federal Emergency Management Agency and the Israeli government now look at it as a planning model. And it’s being extended to include B.C.’s post-secondary institutions.

What makes the program work? The science and engineering may be complicated, but the principle is quite simple: Partnership. The B.C. seismic schools program brings planners, engineers and government together to apply the best science, the best technology, and the best practices from around the world to the task of organizing our effort to make sure our children are as safe as they can be when an earthquake hits.

For example, APEGBC and UBC have developed assessment tools to determine how schools in different seismic zones will withstand different kinds of earthquakes. In addition, APEGBC has developed cutting-edge guidelines for engineers to follow when planning seismic upgrades to ensure the work is done to the best technical standard. And critical research data from around the world has been brought together in one place to assist in engineering assessments and designs.

The bottom line: because of the mitigation program, B.C. has a smart science-based approach to protect our children in an earthquake, allowing government to efficiently target resources where they’re most needed.

Protecting B.C.’s schools from a significant earthquake is only one part of a much larger emergency preparedness plan. The Christchurch earthquake damaged more than 10,000 homes, destroyed 7,500 more, and resulted in the demolition of 1,400 buildings. The total loss: more than $30 billion, or ten per cent of New Zealand’s GDP. That was in a city the size of Victoria. Imagine the economic impact if a similar sized earthquake hit Metro Vancouver.

To meet this challenge, APEGBC will recommend as part of the consultation process that the B.C. government apply the school seismic mitigation model to all public buildings and critical economic infrastructure. Adopting the application of common risk evaluation guidelines will allow all levels of government and the private sector to better organize and target limited resources. In addition, APEGBC recommends that the core operations of government be included in this evaluation. If an earthquake was to hit Lower Vancouver Island while the legislature was in session, for example, the damage to B.C.’s Parliament buildings could have severe consequences on the operation of government in an emergency.

A significant and damaging earthquake will hit B.C.’s south coast. How we plan for it and respond is up to us. In partnership with B.C.’s provincial government and leaders in the scientific community, B.C.’s engineers and geoscientists have helped B.C. lead the way protecting our children in their schools. Working together, we can use that experience to better protect us all.

Ann English is CEO and registrar at the Association of Professional Engineers and Geoscientists of BC.

Source: http://www.vancouversun.com/news/Opinion+started+with+schools+must+prepare+other+structures/9655842/story.html

Cobourg, Ont., feels mild earthquake

A minor earthquake caused some light rumbling under Lake Ontario east of Toronto late Wednesday, the U.S. Geological Survey says.

The quake, which had preliminary magnitude of 2.9, happened just before midnight. The epicentre was 40 kilometres southwest of Cobourg, Ont., and 57 kilometres northeast of Lockport, N.Y.

A map on the agency’s website shows the epicentre in the middle of the lake. The agency says it was about five kilometres deep.

The U.S. Geological Survey posts reports on its website from people who report feeling an earthquake. As of 8:20 a.m. Thursday, six people reported feeling the quake — three in upstate New York and three in Ontario.

The three Ontario reports came from Cobourg, Waterford and Port Hope.

Source: http://www.cbc.ca/news/canada/toronto/cobourg-ont-feels-mild-earthquake-1.2535312

Vancouver would shake more than previously thought during earthquake: studies

The authors say people driving in vehicles would notice the shaking and suggest it could damage even well-constructed buildings.

New research is shaking the entire notion of what could happen to Metro Vancouver during an earthquake, indicating the area would rock harder and longer from a quake than would other areas given the shape and composition of the ground on which it rests.

Two studies published Monday in the Bulletin of the Seismological Society of America show that seismic waves would be amplified as they pass through the Georgia Basin, the deposit of softer sedimentary rock that lies partly beneath Metro Vancouver. The findings have officials assessing the earthquake readiness of infrastructure throughout the region.

That amplification could make the ground shake three to four times harder that it would in a different region.

The researchers ran eight separate scenarios and found that a major quake near Metro Vancouver would most likely register a seven on the Modified Mercalli scale, which measures earthquake intensity on a scale of 1 to 12. The damage to well-designed buildings in the area would be negligible in an earthquake of that intensity, while older structures would be hit hard, according to the U.S. Geological Survey.

But a different region standing on solid ground would experience an earthquake of the same magnitude as just five on the scale, meaning dishes and windows could break and pendulum clocks may stop.

“The shaking in (Metro) Vancouver would be greater because of the presence of the Georgia Basin, especially when the earthquake occurred to the south or southwest,” says lead author Sheri Molnar, with the University of B.C.’s civil engineering department.

She said the waves would spread outward from the earthquake and would have to cross the deep southeast portion of the basin before hitting Vancouver. That would tend to cause the greatest increase in motion.

The Georgia Basin is shaped like an elongated bowl and lies beneath the Georgia Strait, encompassing southwestern B.C., the eastern half of Vancouver Island and northwestern Washington state. It is one in a series of basins along the Pacific coast of North America, and is filled with layers of silt, sand and glacial deposits. The effects of an earthquake on a basin in Canada had not been studied until now.

Molnar compared the Georgia Basin to gelatin surrounded by a hard block of cheese.

“We’re bringing the earthquake up through the cheese, and then it’s suddenly hitting the Jell-O mould and starting to slosh around and bounce around within that Jell-O.”

British Columbia sits on what’s known as the Cascadia subduction zone, where earthquakes tend to occur either within the Juan de Fuca plate or the overriding North America plate. Big subduction earthquakes, like the one that struck Japan in 2011, also occur in the Juan de Fuca plate.

Molnar’s studies examined the potential impact of deep earthquakes, with a magnitude of 6.8, that occur 40 to 50 kilometres beneath the surface, as well as shallow earthquakes of the same magnitude.

Molnar and her colleagues used computers to look at the impact on tall buildings or long structures. Using three-dimensional simulations of different scenarios, the team found that both deep and shallow earthquakes led to greater shaking if the seismic energy moved through the Georgia Basin.

Scientific research had already suggested that softer ground would create worse shaking than bedrock during an earthquake, said Greg Smith, a director of IT and emergency management at Metro Vancouver, who said he did not yet have a chance to see the study.

“We have done work based on ground types and shaking,” said Smith, who added that his team was now working on maintaining communications between municipalities in the event of a quake.

But Natural Resources Canada researcher John Cassidy, who supervised Molnar’s study, said the work shows the basin could also influence the duration of rippling felt above.

“Essentially what the basin is doing is producing stronger shaking and producing longer-duration shaking,” said Cassidy. “Instead of perhaps feeling strong shaking for 10 seconds, you might feel strong shaking for 20 or 30 seconds.”

Cassidy says the model showed that the area beneath the Georgia Strait shook the most.

When earthquake waves hit the southeast part of the Georgia Basin before reaching Metro Vancouver, southwestern areas such as Delta, Ladner and Richmond experienced tremors three or four times what they would be if the Georgia Basin were not there.

However, if the waves hit the northwestern or northeastern part of the basin, they took a different path and either did not affect the Vancouver area or did not cause a significant increase in motion. Cassidy said the findings will help seismologists determine where to place more instruments to record future earthquakes. He also said the findings can be used to upgrade codes for buildings, bridges and other infrastructure to make them more structurally sound.

“The best defence against earthquakes is through good, modern building codes,” he said. “If somebody is planning to put cables in the sea floor or any sort of infrastructure on the sea floor, this is really important information.”

The duration effect is important, said Graham Taylor, a member of the seismic peer review committee of the Association of Professional Engineers and Geoscientists of B.C., who helped developed the seismic retrofit guidelines for B.C. schools. He said buildings are pushed to their limits when the shaking keeps going.

“It’s good research,” he said, adding it will be considered when the Ministry of Education produces the next version of the guidelines. “This is going to just more keenly focus the need … on looking at the duration effect even more.”

But he said the guidelines are already designed for very strong earthquakes and the new research doesn’t mean newly retrofitted schools are now out of date or the guidelines should go out the window.

For Patti Bacchus, the head of the Vancouver school board, the studies underscored the importance of getting work started on the nearly 50 schools she said are cited as being high risk of structural damage in an earthquake.

“We have to make this a priority,” she said. “I can’t think of a more important job to get done.”

She applauded the province for promising money for upgrades, but said thousands of students would still be at risk until the work was done.

Frank Huber, a Metro Vancouver manager of water projects, said he couldn’t comment directly on the newly released study, but added that the region was still a decade or two away from completing its necessary infrastructure upgrades.

“We’re partway there, but not 100 per cent,” said Huber, who noted the area’s major dams were already seismically upgraded, but work remained on pipes under the Burrard Inlet that carry water from the North Shore.

He said the Greater Vancouver Water District now has about half of its pumping stations and reservoirs able to resist a major earthquake, but the rest are not yet ready.

Source: http://www.vancouversun.com/news/Vancouver+would+shake+more+than+previously+thought+during+earthquake+studies/9409158/story.html

A look at British Columbia’s biggest earthquakes

British Columbia has a history as Canada’s hub of seismic activity, with fully half of the country’s top 10 temblors taking place in that province. Here are the five most significant earthquakes to hit the area:

1700: When a quake believed to have a magnitude of nine rolled through B.C.’s Cascadia Subduction Zone, the technology didn’t exist to document it thoroughly. But the tsunami generated by the temblor was chronicled in Japan, placing the exact date on Jan. 26. First Nations folklore suggests the tsunami destroyed an entire village on Vancouver Island’s Pachena Bay, leaving no survivors.

1946: Chaos reigned on Vancouver Island when a 7.3-magnitude earthquake struck on Jun. 23, killing two people. There were reports of extensive property damage as chimneys toppled and building facades crumbled. The quake also triggered landslides across the central part of the island.

1949: On Aug. 22, Canada registered its largest earthquake since Confederation when a magnitude 8.1 tremor struck along the Queen Charlotte Fault (Canada’s closest equivalent to the infamous San Andreas Fault in California). Although the quake was felt as far north as the Yukon, the sparse population of the affected area meant there were no casualties.

1970: The Queen Charlotte Fault struck again on Jun. 24, causing a magnitude 7.4 quake to hit the offshore Haida Gwaii region. Once again there were no fatalities.

2012: When a 7.7-magnitude temblor rolled through the Haida Gwaii region on Oct. 27, it was felt across most of north-central B.C. including Prince Rupert and Quesnel. The earthquake triggered tsunami warnings and serious social media chatter, but resulted in little property damage and no known fatalities.

Source: Earthquakes Canada

Source: http://www.vancouversun.com/news/look+British+Columbias+biggest+earthquakes/9409135/story.html

It’s high time Victoria heeds seismic wake-up call on legislature building

Governments from Washington to California have shelled out to protect their seats of government. The B.C. government should too.

When a magnitude-6.8 earthquake rumbled through Washington state a dozen years ago, it loosened pillars, separated plaster and cracked the 87-metre-high dome at the venerable capitol building in Olympia.

The damage could have been worse. The capitol building, home to the state legislature, had been roiled by quakes in 1949 and again in 1965, which prompted significant structural upgrades.

Still, the third quake in a little over 50 years compelled the state to redouble efforts to preserve what was widely regarded as one of its most historic buildings, as well as one of the most beautiful.

Over the four years following the Nisqually quake of February 2001, the state shelled out $120 million (U.S.) on a combined seismic upgrade and renovation of the capitol, putting a building that opened in 1928 on track for a second century.

Neighbouring Oregon has experienced first-hand the seismic vulnerability of its own state house in Salem. Twenty years ago, a 5.6-magnitude quake cracked the dome, shifting the statue of a pioneer on top of the capitol and forcing closure of the rotunda until $4 million worth of repairs were completed two years later.

To mark this year’s 75th anniversary of the capitol, the state has launched a more ambitious renovation and retrofit. The $300-million project will ensure the graceful art deco structure is able to withstand a magnitude-7.0 quake.

Los Angeles spent $300 million to retrofit its city hall following the 6.7-magnitude Northridge quake in the 1990s. The 32-storey structure, made famous in television shows and movies from Dragnet to the Bad News Bears, is now engineered to withstand an 8.2-magnitude shaker, not unthinkable in Southern California.

Oakland, California considered abandoning its city hall after the structure sustained major damage in the 6.9-magnitude Loma Prieta quake of 1989. Instead, the city spent $85 million on a retrofit that “floated” the Beaux-Arts style building on rubber bearings allowing it to shift as much as 50 centimetres from side to side during a seismic event.

Some 280 “base isolators” were key to a recent renovation and seismic retrofit of the state house in Salt Lake City, Utah, that readied the structure to withstand a 7.3-magnitude quake. Price tag: $260 million.

Each of the aforementioned jurisdictions recognized the inevitable: sooner or later, in a geologically active region like the one we share with them, a major earthquake will inflict serious damage or perhaps even collapse on the structure that is the seat of government. They also faced up to the not-inconsiderable cost of preserving a heritage building that was as old as it was irreplaceable.

But here in B.C., both government and Opposition have balked at addressing the no-less-real threat to the more than-100-year-old provincial legislature building.

“When every last elementary school in B.C. has been seismically upgraded, then we can attend to this building,” as New Democrat John Horgan put it just the other day, and he was speaking for members on both sides of the house.

The occasion was a report to the all-party legislative assembly management committee on the imminent need to spend $6 million rectifying a shift in the dome of the legislature. Part of a projected $70 million worth of repair and maintenance that ought to be done sooner than later. Both preludes to a full-blown seismic retrofit, estimated at a quarter of a billion dollars, maybe more.

Real money to be sure, and one can readily understand why cautious politicians would hesitate to spend it on making their workplace safer for themselves, as many would see it.

But the value of “the ledge,” as it is known colloquially in the capital, is not as an occasional (lately very occasional) debating chamber for politicians. Nor is it simply a matter of preserving any old building. Though the adjacent armoury building, where my office is located, is even older, I wouldn’t waste $1 preserving it because it is as ugly as it is ready to fall down in a stiff wind.

The legislature building merits special treatment for historical as well as architectural reasons. Its unique status is validated by the almost 90,000 people who visit every year, including — ahem — the many children who attend some 350 special school tours.

The province is spending hundreds of millions of dollars seismically retrofitting bridges, hydroelectric dams, transmission lines, all manner of public buildings, and even a sports stadium. Our most irreplaceable heritage structure deserves a place on the priority list as well.

The last government to fully recognize the importance of the place was the one headed by Dave Barrett. His 1972-75 New Democratic Party government launched the first extensive restoration of the legislature, committing $40 million at a time when the annual provincial budget for museums, art galleries and libraries was $4 million.

Forty years later, a similarly inspired exercise is no less overdue, albeit on a schedule that might well be spread over a decade or two for the full-blown restoration and retrofit.

Ideally, it would start with the appointment of an independent panel, endorsed by all parties but separated from any bad feelings about today’s crop of politicians, and dedicated to coming up with a plan for saving what is surely the finest building in B.C.

Source: http://www.vancouversun.com/opinion/columnists/Vaughn+Palmer+high+time+Victoria+heeds+seismic+wake/9238504/story.html