When is a major earthquake expected?

A series of earthquakes off the coast of British Columbia has forced many to remember something they might rather forget: At any moment, a “big one” could strike about 100 kilometres west of Vancouver Island.

In the context of Canada and the Pacific Northwest of the United States, the term “major earthquake” refers to a large earthquake occurring along the Cascadia subduction zone, where the Juan de Fuca tectonic plate meets the North American tectonic plate. The Cascadia subduction zone stretches approximately 1,000 kilometers from northern California to Vancouver Island and is capable of generating earthquakes as large as magnitude 9 on the Richter scale, especially toward its northern end.

Researchers say they know the “big one” is coming, but when should we expect it? Predicting when a big earthquake will strike is just a game of chance, scientists say.

It’s like guessing which breath will make a balloon pop, says Ed Nissen, a researcher in earth and ocean sciences at the University of Victoria. Past experience can give you a sense of it, Nissen says, but no two breaths or balloons are the same. It’s not an exact science.

“Tectonic stress builds up gradually along the faults, and eventually the stresses will overcome the friction and the fault will slip in the event of an earthquake,” Nissen told CTVNews.ca via Zoom.

Scientists can't say when these pressures will be enough to cause a sudden slide, but they can produce rough estimates based on probabilities, Nissen said.

When is a major earthquake expected?

Camille Brion, a seismologist with Natural Resources Canada (NRCAN), says the chance of a strong earthquake off the coast of British Columbia in the next 50 years is between 10 and 15 per cent, with the probability increasing over time.

“So, sometime in the next 200 years or so, there is likely to be a magnitude 9 or greater earthquake in Cascadia,” Brion said, adding that scientists are able to make estimates like this based in part on data from previous large earthquakes along the fault.

According to NRCAN, there have been 13 major earthquakes along Cascadia in the last 6,000 years, at a rate of one every 500 to 600 years. However, some have occurred as much as 200 years apart, while others have occurred as much as 800 years apart.

The last time this happened was more than 300 years ago, Nissen says.

“The next earthquake may not happen for a hundred years or even two hundred years,” Nissen said. “But it's also true to say it could happen tomorrow. It wouldn't be a big surprise.”

How bad was the last “big accident”?

Details of the recent massive earthquake are “very well known,” Nissen said, thanks to oral histories from indigenous people living on Vancouver Island, as well as careful records in Japan.

The last major earthquake along the Cascadia subduction zone occurred at 9 p.m. Pacific time on January 26, 1700. The National and Regional Survey says it was one of the largest earthquakes in the world, estimated to have measured 9 on the Richter scale.

To provide a sense of scale, Nissen said a magnitude 9 earthquake releases 1,000 times more energy than a magnitude 7 earthquake, which NRCAN classifies as a “major” earthquake.

The 1700 earthquake collapsed the homes of the Cowichan people on Vancouver Island and caused numerous landslides, according to the Natural Disaster Monitoring Network of Canada. The quake was so strong that people could not stand, and it lasted long enough to make them sick.

Fog rises over the water outside the village of Anacla in Pashina Bay, British Columbia, Wednesday, Jan. 14, 2015. The Canadian Press/Jonathan Hayward

On the west coast of Vancouver Island, a tsunami triggered by the earthquake completely destroyed the winter village of the Pashina Bay people, leaving no survivors. The tsunami swept across the Pacific Ocean, causing widespread destruction as far away as Japan, where recordings of the events allowed the precise time of the earthquake to be known.

The earthquake also left clear geological signatures consistent with the 12 other earthquakes that preceded it.

Will there be any warning signs?

Nissen said there were unlikely to be any signs that a “big earthquake” was about to hit the area, because earthquakes happen suddenly.

“There is nothing fixed that can be reliably used as an indication that an earthquake will occur,” he said.

Some researchers see promise in studying the tremors that occur before some major earthquakes, but Nissen says even those tremors aren't reliable enough to rely on.

“It turns out that not every earthquake has a precursor. Most big earthquakes don't actually have a precursor,” he said.

Fortunately, a new technology has emerged that can give people enough time, before the tremors start, to try to get to safety.

Brion explained that earthquake early warning systems use special sensors to detect the first wave of energy radiated from an earthquake, the P wave.

“By knowing when the P wave arrives, we can quickly determine where the earthquake is, how strong it is, and then when the next shear waves, or S waves, will arrive at a certain point, and how strong the shaking will be,” she added.

While both types of seismic waves can cause vibrations, S waves are known to be more destructive.

The sensors transmit this information to data centers that use algorithms to determine the earthquake's location and magnitude, and an alert sometimes warns people in the area “tens of seconds before” shaking begins, according to NRCAN.

Canada has developed an earthquake early warning system that is scheduled to be launched soon, Brion said, and ongoing efforts to enhance technology over the Cascadia Fault could give people more time to prepare, Nissen said.

“We’re talking about 30 seconds before those seismic waves hit Vancouver Island … or a little bit longer if you live in Vancouver, which is obviously to the east and further from the fault,” Nissen said. Such a warning wouldn’t prevent damage to buildings and other infrastructure, but it could save lives, he added.

“It's about giving people a few seconds to hide under the table or run outside if they have enough time…trains stopping safely, elevators getting to the nearest floor and doors opening, heart surgeons putting their instruments away, that kind of thing.”

“The most dangerous section”

Meanwhile, a group of 20 researchers has obtained what they say is the most detailed imaging of the Cascadia subduction zone to date, providing valuable insight into how a massive earthquake might develop in the future.

Using a research vessel towing an array of geophysical instruments across almost the entire area, scientists have been able to produce what they say is the first comprehensive survey of the complex structure of the fault beneath the seafloor.

The team published its research in the scientific journal Science Advances last June.

A couple walks along Whiffin Spit Park after a tsunami warning in Sooke, British Columbia, Tuesday, Jan. 23, 2018. THE CANADIAN PRESS/Chad Hipolito

“The models currently used by public bodies have been based on a limited set of low-quality, legacy data dating back to the 1980s,” said Susan Carbot, lead author and marine geophysicist at Columbia University, in a press release. “The massive thrust has a more complex geometry than previously assumed. The study provides a new framework for assessing earthquake and tsunami risk.”

Among the study's findings is that the northern part of the fault, near Vancouver Island and Washington state, is the section most likely to produce a major earthquake.

While the terrain of the other parts is relatively rough, with features that may erode the upper plate and limit the extent of any earthquake propagation within the part, the northern part is smooth.

“This means it may be more likely to rupture along its entire length at one time, making it the most dangerous section,” the press release said.

What Are The Main Benefits Of Comparing Car Insurance Quotes Online

LOS ANGELES, CA / ACCESSWIRE / June 24, 2020, / Compare-autoinsurance.Org has launched a new blog post that presents the main benefits of comparing multiple car insurance quotes. For more info and free online quotes, please visit https://compare-autoinsurance.Org/the-advantages-of-comparing-prices-with-car-insurance-quotes-online/ The modern society has numerous technological advantages. One important advantage is the speed at which information is sent and received. With the help of the internet, the shopping habits of many persons have drastically changed. The car insurance industry hasn't remained untouched by these changes. On the internet, drivers can compare insurance prices and find out which sellers have the best offers. View photos The advantages of comparing online car insurance quotes are the following: Online quotes can be obtained from anywhere and at any time. Unlike physical insurance agencies, websites don't have a specific schedule and they are available at any time. Drivers that have busy working schedules, can compare quotes from anywhere and at any time, even at midnight. Multiple choices. Almost all insurance providers, no matter if they are well-known brands or just local insurers, have an online presence. Online quotes will allow policyholders the chance to discover multiple insurance companies and check their prices. Drivers are no longer required to get quotes from just a few known insurance companies. Also, local and regional insurers can provide lower insurance rates for the same services. Accurate insurance estimates. Online quotes can only be accurate if the customers provide accurate and real info about their car models and driving history. Lying about past driving incidents can make the price estimates to be lower, but when dealing with an insurance company lying to them is useless. Usually, insurance companies will do research about a potential customer before granting him coverage. Online quotes can be sorted easily. Although drivers are recommended to not choose a policy just based on its price, drivers can easily sort quotes by insurance price. Using brokerage websites will allow drivers to get quotes from multiple insurers, thus making the comparison faster and easier. For additional info, money-saving tips, and free car insurance quotes, visit https://compare-autoinsurance.Org/ Compare-autoinsurance.Org is an online provider of life, home, health, and auto insurance quotes. This website is unique because it does not simply stick to one kind of insurance provider, but brings the clients the best deals from many different online insurance carriers. In this way, clients have access to offers from multiple carriers all in one place: this website. On this site, customers have access to quotes for insurance plans from various agencies, such as local or nationwide agencies, brand names insurance companies, etc. "Online quotes can easily help drivers obtain better car insurance deals. All they have to do is to complete an online form with accurate and real info, then compare prices", said Russell Rabichev, Marketing Director of Internet Marketing Company. CONTACT: Company Name: Internet Marketing CompanyPerson for contact Name: Gurgu CPhone Number: (818) 359-3898Email: [email protected]: https://compare-autoinsurance.Org/ SOURCE: Compare-autoinsurance.Org View source version on accesswire.Com:https://www.Accesswire.Com/595055/What-Are-The-Main-Benefits-Of-Comparing-Car-Insurance-Quotes-Online View photos