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Several earthquakes strike off Vancouver Island, with no reports of damage

A series of three large earthquakes have struck off the coast of British Columbia, according to the United States Geological Survey.

There were no immediate reports of casualties or damage from the quakes.

The first struck just before 11 p.m. PT Sunday, around 190 km southwest of Port Hardy, a town on the northeast end of Vancouver Island.

The first quake, reported as a magnitude 6.5, was followed by another, with a magnitude of 6.8, around 40 minutes later.

The third quake was reported at magnitude 6.5 just before midnight, near the same area as the previous two.

Three in a row ‘unusual’

CBC meteorologist and seismologist Johanna Wagstaffe said the earthquakes are a reminder that B.C. is in a “complicated” tectonic setting.

British Columbia is located on the Pacific Ring of Fire, an active seismic zone where thousands of mostly small earthquakes are recorded annually by sensors in the province.

Most of the quakes happen near the Cascadia subduction zone, an area where the Juan de Fuca and North American tectonic plates converge, stretching from Vancouver Island to northern California.

“If any one of these quakes had hit closer to land, there would have been devastating consequences,” said Wagstaffe about the Sunday-Monday quakes.

“Three large ones in a row does seem unusual, and I’m sure scientists will be learning as much as they can over the next couple of days about the change in stresses just off our coast.”

There were no immediate tsunami warnings following the earthquakes.

Earthquakes Canada also reported a magnitude 4.4 aftershock from the first quake before midnight, and three below magnitude 5.0 early Monday.

Source: https://www.cbc.ca/news/canada/british-columbia/bc-earthquakes-1.4872470

New findings clarify the seismic risk in the Pacific Northwest

How bad would a Cascadia Subduction Zone earthquake be for the Pacific Northwest?

In the last month, several studies were published which not only showcase the dangers posed by this 1,000 km-long (600 mi) plate boundary, but highlight where ruptures may be most likely. The findings show that in the cities of Portland and Seattle, the quake could leave hundreds of thousands of properties damaged and destroyed, and that in places like Seattle, which lies in a sediment-filled basin, shaking could be much more severe.

Three years ago, Kathryn Schultz’ Pulitzer Prize-winning New Yorker essay, The Really Big One, thrust the Cascadia Subduction Zone into the public spotlight. While the convergent plate boundary, which extends from Vancouver Island at its north end to California’s Cape Mendocino at the south, had been known to scientists for decades, the article renewed public interest and scientific focus.

Major population centers exposed to significant risk

The two largest cities in the Pacific Northwest, Seattle and Portland, are home to several million people. In the event of a M=9 earthquake, which is what Cascadia is capable of, the impact would be severe. Part of this is due to proximity to the plate boundary to theses urban centers, but also the geology.

The city of Seattle, the nation’s fastest-growing city, lies in the Puget lowland on the shores of Puget Sound and Lake Washington. While the location creates an ideal trade gateway, it also means the city lies atop a deep basin. This has startling consequences for shaking, according to a recent study by scientists at the University of Washington, the USGS, and University of Southern California. They looked at how buildings ranging from 4-40 stories high would sway (engineers call this “drift”) in simulated earthquakes, comparing the ride in the Seattle basin, and outside it. They found that within the basin, buildings swayed at least three times more than outside of it because of stronger, slower shaking. Thus could result in much greater levels of damage throughout the city, and longer recovery times.

In Portland, 233 km (145 mi) south of Seattle, the situation is not much better. The Oregon Department of Geology and Mineral Industries (DOGAMI) recently published an updated scenario of what a M=9 Cascadia event could do to the city. By assessing the shaking throughout the metropolitan area, they found approximately 38-39% (235,000) of the city’s buildings would suffer some level of damage. This emphasizes, is that in the event of a Cascadia event, the impacts will not only be extremely severe, but extremely widespread.

Where is a great rupture most likely to happen?

While scientists do not know where a rupture will strike, there are clues that point to areas which may be more susceptible. Two of these are ‘locking,’ and seismic ‘tremor.’ As tectonic plates move against one another, stress builds up. Eventually, the stress reaches a critical level, the fault leaps forward and an earthquake takes place. Where plates are “locked,” the amount of stress that can be built up is greatest. Therefore, identifying the most locked portions of the Cascadia Subduction Zone sheds light on areas of greatest risk. The figure below shows that along the plate boundary, locking is greatest in Washington on the one hand, and Southern Oregon and Northern California on the other. Northern Oregon shows quite a bit.

Seismic tremor, which accompanies slow slip events, is common along parts of the Cascadia subduction zones. Tremor seems to be another indication that the fault is locked above a certain depth, but is firing off in very small shocks and slippage just below that depth.

In fact, over the last two weeks, tremor has picked up in Northern Washington, Southern Oregon, and Northern California, as the map from the Pacific Northwest Seismic Network below shows.

Slow slip events are not like regular earthquakes, which last for tens of seconds, but instead last for days to weeks. These events locate just below the locked portions of the fault, and are accompanied high frequency vibration or ‘tremor.’

While scientists are still unsure if periods of intense tremor, such as has occurred for the past two weeks, can presage large earthquakes, strongly-locked tectonic plates tend to produce the largest and most frequent megaquakes. And, a recent study by University of Oregon and University of New Mexico scientists shows that the higher levels of locking and tremor in certain parts of the Pacific Northwest are likely permanent features.

What does this mean for the Pacific Northwest?

Seattle, Portland, and Vancouver B.C. all lie within the zones of elevated tremor and strong locking. In contrast, Eugene lies inland of the portion of the megathrust that is not strongly locked and that produces less tremor. Therefore, the new evidence only confirms and highlights the risk for Vancouver, Seattle, and Portland, and perhaps reduces it for Eugene.

Source: http://temblor.net/earthquake-insights/new-findings-clarify-the-seismic-risk-in-the-pacific-northwest-7443/

4.2-magnitude B.C. earthquake occurs off coast of Haida Gwaii

Once again, the earth was shaking in Haida Gwaii, which is also known as the Queen Charlotte Islands.

That’s because of a 4.2-magnitude shaker that occurred on Saturday, appoximately 15 kilometres underground off B.C.’s north-central coast.

The epicentre was off the northwestern tip of the archipelago.

According to Natural Resources Canada, the effects were “lightly felt” in Masset.

There were no reports of damage or any injuries.

Several other earthquakes have occurred in this region in recent years, including a 6.1-magnitude earthquake in April 2015 and a 7.7-magnitude earthquake in October 2012.

There was also a 7.9-magnitude earthquake in Alaska in January centred near Kodiak Island.

Source: https://www.straight.com/news/1084391/42-magnitude-bc-earthquake-occurs-coast-haida-gwaii

Here’s why the tremor that shook Windsor-Essex was a ‘good earthquake’

What did you do when the earth started shaking Thursday night?

Chances are you ran out into the street to ask friends and neighbours if they felt it too.

While that reaction is understandable, CBC meteorologist Johanna Wagstaffe says the safest thing to do when the windows start rattling is to follow three simple instructions: drop, cover and hold on.

Environment Canada initially said the earthquake had a magnitude of 3.9, but upgraded the measurement to 4.1 Friday. The U.S. Geological Survey (USGS) categorized the quake as a magnitude 3.6. The Canada and U.S. counterpart use different scales to measure earthquakes, and CBC News reported the USGS numbers primarily, because Canadian data was not yet available.

Wagstaffe said the quake is a great reminder to make sure your family has an emergency safety kit and knows what to do in a disaster, she added.

“These are what I call good earthquakes,” she explained. “People are talking about them and there are no injuries or damages, but it’s a reminder that even though most of the earthquake action happens in B.C., we do get earthquakes right across the country, and it’s a reminder you should know what to do when an earthquake happens.”

Earthquakes are rare for southwestern Ontario because the area sits over a very stable section of the tectonic plate.

Wagstaffe said seismologists will use data from previous quakes to try to figure out what caused it — old faults running through the region or movement caused by parts of the continent slowly rebounding after the last ice age are two possibilities.

“It looks like it struck fairly shallow, just five kilometres below Amherstburg,” she explained. “It was pretty widely felt. I mean, it was shallow enough, even though it was a fairly weak earthquake, that a few million people felt weak to light shaking.”

So what should you do when the next quake hits?

“If you feel shaking, immediately try and get under a desk or a sturdy object because most deaths and injuries that happen in cities similar to Canadian cities happen because of falling objects or because people are trying to run outside.”

Source: http://www.cbc.ca/news/canada/windsor/amherstburg-earthquake-johanna-wagstaffe-1.4628005

3.6-magnitude earthquake hits south of Windsor, Ont.

A 3.6-magnitude earthquake has hit the community of Amherstburg, more than 20 kilometres south of downtown Windsor.

According to the U.S. Geological Survey, the earthquake happened just after 8 p.m. on Thursday.

It was measured at a depth of 7.8 kilometres.

Amherstburg police said in an update on Twitter that there were no reports of damages.

Residents in Windsor and Detroit, Michigan reported feeling tremors at the time of the earthquake.

According to Earthquakes Canada, the Geological Survey of Canada records approximately 4,000 earthquakes in Canada yearly with most happening on the west coast. However, only about 50 of those earthquakes are generally felt by residents.

Source: https://globalnews.ca/news/4156446/earthquake-amherstburg-ontario/

Tsunami warning ends for B.C. after large earthquake strikes off Alaska

A tsunami warning for coastal British Columbia and parts of Alaska has ended after a powerful earthquake struck about 250 kilometres southeast of Chiniak, Alaska, early today.

The quake struck at 1:31 a.m. PT Tuesday and prompted a tsunami warning for the entire B.C. coast and a tsunami watch for the entire U.S. West Coast.

In Port Alberni, a city that was devastated by a tsunami in 1964, Mayor Mike Ruttan activated the four tsunami sirens at around 3 a.m. PT, alerting 17,000 residents to move to higher ground.

“The warning was repeated every 10 minutes for two minutes [in duration]. They’re very loud, there’s no way you can ignore them. And then in between time, the paper mill was blowing its horns for extended periods of time to let people know there was civic emergency.”

Ruttan said although the city could have communicated better on social media, the evacuation was orderly.

“I am pleased with the response for the most part,” he said.

In Tofino, on the west coast of Vancouver Island, warning sirens were activated on the two main beaches in town, and hundreds of people evacuated to the emergency reception centres at the community hall and an elementary school.

“Everything has proceeded in a really orderly fashion,” said Tofino Mayor Josie Osborn. “This is why we train, this is why we do exercises and this is why spend time making emergency plans and then testing them.”

The provincial emergency systems worked the way it was supposed to, said B.C.’s public safety minister.

“Whether it was in Esquimalt where we saw firefighters and first responders going door to door, or… Queen Charlotte City which was fully evacuated, or the sirens in Tofino and Ucluelet, and people going to their local emergency centres, people responded admirably and I think the emergency services did a remarkable job,” said Mike Farnworth.

The U.S. Geological Survey initially reported the quake’s strength at 8.2 early Tuesday and later revised that to 7.9, with a depth of 25 kilometres. At least three aftershocks were reported.

“This is a place in the world where we see historically a lot of large earthquakes,” said CBC seismologist Johanna Wagstaffe.

Wagstaffe said early data showed the movement of tectonic plates under the ocean was more of a side-to-side motion than what’s known as a mega-thrust.

“Mega thrusts are the ones we really worry about when it comes to widespread and large tsunamis because there is so much more vertical displacement of the ocean floor,” she said.

“Side-to-side can definitely still generate a tsunami, and again we are seeing a small one, but this motion doesn’t generate as large of a tsunami as what we would get with a mega-thrust.”

Emergency Info BC warned people in the affected area to move away from the water, off beaches, and away from harbours, marinas, breakwaters, bays and inlets. Boat operators were advised to move their boats out to sea to a depth of at least 55 metres.

Trevor Jarvis, the emergency co-ordinator for the Village of Masset on the north end of Haida Gwaii, said he sent out an emergency text to residents and set off the tsunami emergency siren just after 2 a.m. on Tuesday. Everyone on the north end of the village was told to get to higher ground.

The quake struck 280 kilometres southeast of Kodiak, Alaska. People reported on social media that it was felt hundreds of kilometres away in Anchorage. Some said they saw the water retreating in Kodiak harbour, a possible sign that strong waves could return.

However, Kodiak police later said the tsunami warning was downgraded to advisory. They also said they received two reports that tide levels in the channel were fluctuating “by six inches to one foot.”

The U.S. Pacific Tsunami Warning Centre issued a tsunami watch for the state of Hawaii that was soon cancelled.

Source: http://www.cbc.ca/news/canada/british-columbia/alaska-earthquake-tsunami-1.4499558

Eastern Canada, including big cities such as Montreal, at risk for earthquakes, warns study

While people in British Columbia are mindful of the fact they could eventually face some of the strongest earthquakes in the world, at least one study warns there’s a lack of awareness of the risk in Eastern Canada.

One report released last summer predicts Montrealers could suffer $45 billion in economic losses if the city were to experience an earthquake measuring 5.8 on the Richter scale. That’s the estimated strength of a tremor that hit Montreal in 1732.

Maurice Lamontagne, a seismologist with the Geological Survey of Canada, says 300 houses were damaged back then but if a similar earthquake were to occur now it “would cause a lot more damage.”

The study by Zurich-based Swiss Re, a company that helps cover other insurers, noted that Quebec’s Charlevoix region northeast of Quebec City was hit in February 1663 by a 7.0 magnitude quake.

Lamontagne added that in 1929, an earthquake just off the shore of Newfoundland measured 7.2 on the Richter scale.

The tsunami that followed caused most of the devastation and killed 28 people when it hit the shore.

Each year, there are about 450 quakes in Ontario and all points east.

“You don’t get huge earthquakes like they get in Japan, in California,” Lamontagne said. “But we do get what you call moderate earthquakes, so six to seven on the Richter scale are possible.”

The Swiss Re study, entitled: “Earthquake Risk in Eastern Canada: Mind the Shakes,” says quakes in the East tend to be of lower magnitude than in the West, “but their loss-inflicting potential, particularly in southern Quebec and eastern Ontario, is huge.”

The study points out that three of the biggest cities in Canada — Montreal, Ottawa and Quebec City — are all located in the most earthquake-prone regions of the East.

Two tremors measuring 3.0 and 3.5 were recorded in the Beaupre region on Jan. 2 and Jan. 4 and were felt in Quebec City, about 40 kilometres away.

Pierre Babinsky, a Quebec spokesman for the Insurance Bureau of Canada, says 85 per cent of people it surveyed in 2017 said they didn’t think their home was at risk of being damaged by an earthquake.

“It’s about three per cent of people who have earthquake insurance in the Quebec City area, about four per cent in Montreal,” he said. “And Charlevoix, where they felt a few stronger earthquakes, the average isn’t much higher.”

In B.C., 65 per cent of households have earthquake insurance, according to Swiss Re.

“In the case of earthquake risk in Quebec, most people are unaware — or if they are aware that it’s the second seismic zone in Canada, they don’t believe it will actually affect them,” Babinsky said.

In June 2010, the Parliament Buildings were evacuated following a 5.0 magnitude earthquake near Ottawa. Several buildings are still undergoing major renovations that include seismic reinforcement of foundations and walls.

Babinsky said the insurance bureau has been raising awareness by touring cities in Quebec with a simulator, so people can experience an earthquake of 7.0 magnitude.

“Maybe they just want to prepare their home, maybe they want to get some insurance, it’s up to them,” he said, “But we want them to have the information they need to make that decision.”

It would cost an additional $200 a year for earthquake coverage.

Babinsky stressed the insurance industry has the required capital to cover a major quake, which he said would be about nine on the Richter scale in British Columbia and about seven in Quebec.

“Right now, for all the policies that are out there, both residential and commercial, the industry has enough capital to cover any claims that would occur in one of those types of earthquakes,” he said.

“But if we have two successive earthquakes…then obviously we need to make sure that we’re ready as an industry and as a financial sector to go through that.”

Seismologist Lamontagne says there’s a 45 per cent chance that Charlevoix will have an earthquake over the next 50 years that would cause significant damage. For Montreal, it’s about “maybe 10, 15 per cent over the next 50 years.”

“In 1988, there was a 5.9 quake south of Chicoutimi that was felt everywhere in Quebec and in the coming decades we’ll have another one of that order,” he predicted.

Some tips from Canadian insurance companies about preparing for an earthquake:

— Know the safe and dangerous places in your home; plan and practise evacuation.

— Decide with family members where to meet in case of separation after an earthquake.

— Talk to relatives about what to do if they’re at home, school, or at work and the quake separates your family.

— Place heavy objects on lower shelves to prevent them from falling on someone.

— Secure tall pieces of furniture and shelves, mirrors and furniture on wheels.

— Make sure chemical products are securely stored.

— Don’t forget to practise, Drop, Cover, and Hold On.

Source: http://vancouversun.com/news/canada/potentially-huge-losses-from-future-earthquakes-in-eastern-canada-study/wcm/24e8ab56-418e-45f8-9860-8f9873044e28

Washington state residents rattled by Mount St. Helens tremors

Mount St. Helens is rumbling again, but it’s not the volcano that worries Washington state seismologists the most.

A 3.9-magnitude jolt Wednesday morning, about 11 km northeast of the volcano, was the strongest tremor in the seismically active area since 1981. It was followed by a swarm of up to 150 smaller earthquakes.

In 1980, an eruption blew out the side of the volcano, killing 57 people and devastating the landscape. Cascades of water, mud, and rock raged down valleys and knocked down forests.

But the latest quakes do not signal that the volcano is moving closer to another eruption, seismologist Seth Moran told On the Island host Gregor Craigie.

“There are earthquakes that are occurring at Mount St. Helens kind of continuously,” said Moran, who is a seismologist and scientist-in-charge at the United States Geological Survey’s Cascades Volcano Observatory.

The most hazardous volcano in Washington state is considered by seismologists to be Mount Rainier, where volcanic mud flows, called lahars, roar down the Puyallup River drainage system every 500 to 1,000 years.

“That’s a long time from a humanity perspective, but from a geologic perspective that’s pretty frequent and a really good reason for believing it’s going to happen again,” Moran said.

Tens of thousands of people are in the path of a large lahar, including the Washington communities of Orting, Sumner and Puyallup. In a worst-case scenario the lahar could reach Tacoma, though related flooding is more likely to affect the city.

Moran said the lahar detection system set up two decades ago by Pierce County with USGS assistance is now old technology, but it can be updated to provide more effective and earlier warning for the “bump in the night” event that could give residents as little as 45 minutes to escape to safety.

“We’ve done studies of the volcano itself and there are parts of the volcano, of the cone, that we know are somewhat unstable and have the potential to let loose again with one of these things,” Moran said. “The likely scenario is it wouldn’t happen unless the volcano is in a state of unrest or eruption.”

While the recent earthquake close to Mount St. Helens might seem alarming, Moran said it is not cause for concern.

If magma was moving in the volcano, Moran said, “It would be different. We’ve seen Mount St. Helens wake up twice and in both cases it was pretty obvious what was happening in terms of how different things were or how different things quickly became.”

​When the volcano became active again in 2004, he said, the earthquakes started small and increased in strength and frequency over time instead of decreasing, as they have this week. There were also ground deformations and glacier cracks.

Source: http://www.cbc.ca/news/canada/british-columbia/st-helens-earthquakes-mt-rainer-lavar-mudflow-volcanoes-1.4473612

Light earthquakes strike in northern B.C. and off Vancouver Island

An earthquake hit northern B.C. near Alaska and the Yukon at 4:10 p.m. today (December 18).

The quake was located on land at a depth of 10 kilometres (6 miles) and 53 kilometres (33 miles) northwest of Mosquito, Alaska, and 127 kilometres (78 miles) southwest of Whitehorse, Yukon.

The U.S. Geological Survey has listed it as a 4.1-magnitude event while Earthquakes Canada has listed it measured it as a 4.3-magnitude quake.

Both measurements of the seismic event fall within the light category on the Richter scale, which is stronger than a minor earthquake yet significant damage is unlikely.

Meanwhile, a light earthquake also struck offshore west of Vancouver Island on December 16 at 8:11 p.m.

The epicentre of the 4.2-magnitude quake was located 166 kilometres (103 miles) west of Port Hardy, at a depth of 10 kilometres (6 miles).

A few quakes have struck the area over the past few weeks. On December 5, a 4.0-magnitude quake occurred in the area between Haida Gwaii and Vancouver Island. Before that, a 4.5-magnitude quake struck offshore of Vancouver Island 174 kilometres west of Port Hardy on December 3.

Source: https://www.straight.com/news/1009376/light-earthquakes-strike-northern-bc-and-vancouver-island

Old drawings could assist new earthquake plan at the B.C. Legislature

The imposing British Columbia Parliament Buildings have a fatal weakness: they could collapse in a major earthquake.

The legislature, as the buildings are more commonly known, was built long before modern seismic building codes were adopted. Engineers have identified its iconic dome above the centre block as being particularly vulnerable to damage.

Fixing the century-old structure would be expensive with past estimates pegging a retrofit at somewhere between $700 million and $900 million.

But now the Speaker and legislative officers are working on a proposal that could lead to the construction of a new seismically-robust back-up building.

Craig James, a legislative clerk, said such a plan could draw inspiration from a historic architect.

Francis Rattenbury gained fame in the early 1900’s for a number of landmark buildings, including the B.C. Parliament Buildings and the nearby Empress Hotel.

“One option that we have is to take one of Rattenbury’s drawings to replicate a portion of this building over there, which in looking at it would be spectacular,” said James.

The proposal would see the old brick armoury building that currently stands behind the legislature torn down to make way for a new building.

“That building would in some part replicate on a smaller scale this place,” James said. “But also a larger chamber could be built over there so that in the event that something did happen here and this place was unusable, perhaps we could use it.”

Of course, government does not need an ornate legislative assembly to function. And building a back-up legislative assembly would not be cheap, likely costing tens of millions of dollars. But James notes that is about one-tenth of the cost of retrofitting the legislature itself.

Gary Lenz, the sergeant-at-arms, says ensuring continuity of government and a rapid response to an emergency are important.

“We all form that linkage towards passing of bills and legislation, which is critical if there’s a major earthquake or there’s a major disaster in the province.”

Speaker Darryl Plecas said a new building would play a crucial role in an emergency, and would also make the eventual seismic upgrade of the legislature more feasible.

“We could really be helpful in two ways. One is we help ensure continuity of government because we have a place for people to work. And then we have a place to work whilst we were doing seismic upgrading, so we provide for an enhanced level of safety along the way.”

In the meantime, legislative staff are working on improving the earthquake response plan, including better securing some of the statues atop the building’s exterior.

Other measures already in effect on the grounds include early warning sensors and accessible containers with emergency supplies.

Staff also hope to have early warning apps installed on mobile phones belonging to legislature employees within the coming months.

Source: http://www.cbc.ca/news/canada/british-columbia/drawings-new-quake-plan-bc-legislature-1.4401890