Tag: Cascadia subduction zone

A mega-tsunami in the Pacific north-west? It could be worse than predicted, new study says

Strange Sounds – June 9, 2022

Scientists have discovered the size of the ‘outer wedge’ of a faultline can magnify a rupture’s impact. That’s a worrying news for the people living along the Cascadia Subduction Zone, a fault running from Vancouver Island to northern California…

Scientists have long predicted a giant 9.0-magnitude earthquake that reverberates out from the Pacific north-west’s Cascadia fault and quickly triggers colossal waves barreling to shore.

But what if these predictions were missing an important piece of information – one that, in certain scenarios, could tell an even more extreme story?

A new study, published last month in the peer-reviewed journal Earth-Science Reviews, points toward such a missing piece. Researchers revealed a previously unknown relationship between the severity of a tsunami triggered by an earthquake and something known as “the outer wedge”, the area between the main earthquake fault and the seafloor.

Sylvain Barbot, a co-author of the study, described the outer wedge as the “garbage bag of subduction zones”, the place where two tectonic plates crash into each other and can produce an earthquake, because it’s where sediment piles up.

The researchers’ findings suggest that the wider it is, the larger the maximum size of the tsunami will be.

The connection adds a new element to consider when making tsunami predictions, one that the authors suggest could mean heightened worst-case scenario predictions for some faults, including Cascadia.

https://strangesounds.org

Slow Slip Event on Cascadia Subduction Zone: Vancouver Island hit by more than 4,200 quakes since March 20 – Cascadia about to blow?

Strange Sounds – April 5, 2022

You can’t feel it, but the ground far beneath our feet on south-central Vancouver Island has been moving.

Seismologists have been recording thousands of “episodic tremor and slip events” occurring at a rapid rate since March 20 moving in a southeasterly direction down the Island.

More than 4,200 tiny tremors have been recorded so far between 25 and 40 kilometres below the surface, said John Cassidy, an earthquake seismologist with Natural Resources Canada and a professor at the University of Victoria.

“They’re not earthquakes. … On the instruments they look like series of a trains rolling by,” Cassidy said.

He said these bursts of small tremors and slips occur about every 15 months along faults that form the boundaries of tectonic plates — in our case, the Cascadia subduction zone from Brooks Peninsula on the Island to Northern California, where the Juan de Fuca plate system curves west beneath the North American plate.

The repeated episodes of slow fault slips — measuring about the size of five stacked dimes — usually occur over a period of several weeks, accompanied by tremors that appear on seismic records as prolonged, intermittent ground vibrations, Cassidy said.

The ETS activity has been going on for centuries, but has only recently been recorded using sophisticated GPS technology at more than 40 sites up and down the Island. They differ from earthquakes, which generate large, sharp shock waves that subside very quickly, but ETS can help in improving estimates on where and when the next earthquake might occur, Cassidy said.

By mapping out the areas on the subduction fault where stress is not accumulating over the long term, tremor events define the landward limit of the zone that could rupture during the next great earthquake.

That provides a more accurate estimate of how close the rupture could be to major West Coast cities such as Victoria, Vancouver and Seattle, and what shaking could occur, he said.

https://strangesounds.org

Preparedness: A monstrous earthquake in the Pacific Northwest is a certainty; we just don’t know when

Strange Sounds – January 27, 2022

A monstrous earthquake in the Pacific Northwest is a certainty. We just don’t know when.

For many people, natural disasters inspire both fascination and fear. They’re a sign of nature’s power to not only create, but also destroy. At the same time, they’re a reminder of the human potential for ingenuity when it comes to protecting ourselves from the forces we cannot control.

In this case, there are two opposing forces: the North American Plate, an enormous tectonic plate that carries the entire continental United States on its back, versus the 90,000-square-mile Juan de Fuca Plate, located in the ocean off Washington, Oregon, and Northern California.

For the past 200 million years, these two have been squaring off in an epic wrestling match in an area known as the Cascadia Subduction Zone, or CSZ. Trust us, nobody wants to see the end of this round. Yet only a few people seem truly bothered: seismologists, emergency management professionals, and those who have experienced earthquakes before.

It’s certain that the Northwest will experience a devastating earthquake again, says Chris Goldfinger, an oceanographer at Oregon State University and one of the world’s leading experts on subduction zone earthquakes. “We have no idea of the timing and how urgent it is,” Goldfinger tells Pop Mech. “People tend to ignore it in that case.”

The majority of the public, as well as most governments in the Northwest, aren’t yet pushing to implement the extensive infrastructure changes and early-warning communications systems needed to save tens of thousands of lives.

The Juan de Fuca Plate has been steadily pushing against the Pacific Coast as it slides beneath the North American Plate. But the roughly 47-million-square-mile North American Plate isn’t budging. Instead, it’s locked tightly against the Juan de Fuca’s surface.

Here’s the chilling prediction from the Cascadia Region Earthquake Workgroup (CREW) in its 2013 report on CSZ earthquakes: “Cascadia has now been building up strain for over 300 years, so the next great earthquake could happen at any time.

https://strangesounds.org

Earthquake warning as US and Canada ‘due for major event’: ‘It’s matter of when’

Joel Day – November 5, 2021

It has been centuries since the contiguous US, the entirety of the states, experienced a “Big One” — an earthquake with a magnitude greater than 9.0. The last on record was an earthquake in 1700 with an estimated magnitude of 9.0. This was along the Cascadia subduction zone where the Juan de Fuca plate is diving underneath the North American plate.

Huge earthquakes happen in this region because the plate that’s going down is usually oceanic crust, which is cold and dense, which means it can break in a sharp and sudden manner.

However, the cold dense crust that’s sinking can break for a much longer time and initially result in the seismic shifts and tremors.

The nature of the zone pairs any earthquake with another destructive event: a tsunami.

The earthquake that hit in 1700 sent a tsunami across the Pacific Ocean as far as Japan.

Researchers are now expecting another event at the Cascadia subduction zone, with the chances of it happening in the coming decades explored during NOVA PBS’ short documentary, ‘The Pacific Northwest is due for a Major Earthquake’.

Wendy Bohon, a geologist and senior science communication specialist at the Incorporated Research Institutions for Seismology, explained the process behind how a tsunami would result from an earthquake, and said: “You have one plate diving down beneath another, one section gets locked and it pushes another part up.

“When the fault ruptures, when the amount of stress overcomes the friction, it bounces back, which lifts up the water above it and causes that water to flow out in all directions.

“And that water flowing out in all directions in the tsunami.”

Oral histories of the earthquake and tsunami that hit in 1700 suggest many died from the event.

https://www.express.co.uk

The Shaking In California Is Getting WORSE As Hundreds And Hundreds Of Earthquakes Cause Alarm On The West Coast

– June 6, 2021

Are we getting close to a major seismic event on the west coast?  Within the past several days, we have seen hundreds of earthquakes happen in southern California, there have been large earthquakes offshore near the Cascadia Subduction Zone, and there has been a very alarming swarm of earthquakes at Mt. Hood.  We haven’t seen this much seismic activity along the west coast in quite a long time, and many are concerned that this could be leading up to something really big.

At this moment, scientists are carefully monitoring the area around the Salton Sea.  According to the USGS, in one 24 hour period over the weekend more than 600 earthquakes of at least magnitude 1.0 shook that area of southern California…

More than 600 small earthquakes have been recorded this weekend in a rural area near the Salton Sea in Southern California, with the largest having a magnitude of 5.3, a US Geological Survey geophysicist told CNN.

Geophysicist Randy Baldwin said 603 temblors with a magnitude of at least 1 happened in the area from Saturday to just before sunrise Sunday.

The magnitude 5.3 quake was felt throughout the region.

In fact, it is being reported that it was even felt at an apartment building that was 95 miles away from the epicenter of the earthquake…

People in Chula Vista, San Diego, El Centro and Indio felt the 5.3 quake, according to the USGS, Did You Feel It reports. The tool collects information from people who report they’ve felt an earthquake and creates an interactive map.

Saturday morning’s shaking could be felt in an apartment building near Del Mar, California, approximately 95 miles away from the location of the earthquake.

When I wrote about the alarming rise of earthquake activity on the west coast a week ago, just over 1,000 earthquakes had occurred in California and Nevada over the previous seven days.

Now that number is up to 1,757, and it seems to be going up with each passing hour.

http://endoftheamericandream.com

California on seismic alert: Two shallow M4.6 and M4.4 earthquakes hit off Eureka within seconds – Precursors of the Big One?

Strange Sounds – April 2, 2021

Today morning, two shallow earthquakes (M4.6 and M4.4) hit off the coast of northern California at a depth of 8km and 19km, respectively.The pair of quakes struck 17 seconds apart of each other (8:21:18 and 8:21:35 AM UTC).Some weak or light shaking was probably felt in the Eureka and Fortuna areas.

The third M2.5 quake in the area hit 1 hour after the first two…

Meanwhile, I am sure geologists closely monitor the seismicity along the west coast…

These earthquakes could indeed be precursors of the next Cascadia Megathrust Earthquake or California Big One…

Indeed, the tremors occurred near the Mendecino Triple Junction, an area where the Cascadia Subduction Zone meets with the San Andreas Fault.

Moreover, if you look at the map from PSNS below, additional quakes rattled the Cascadia Subduction Zone off the Oregonian coast and on Victoria Island in Canada, as well.

An earthquake will destroy a sizable portion of the coastal Northwest.

The question isn’t if but when. And keep in mind: The next full-margin rupture of the Cascadia subduction zone will spell the worst natural disaster in the history of the continent.

https://strangesounds.org

New Active Earthquake Faults Discovered Near Mount Hood Could Trigger M7.2 Quake And Devastate Everything As Far As Portland, Oregon

Strange Sounds – March 24, 2020

Mount Hood is a potentially active stratovolcano in the Cascade Volcanic Arc of northern Oregon.

Researchers have newly discovered active fault lines on Mount Hood that could potentially trigger a 7.2 magnitude earthquake, devastating communities and infrastructure as far west as Portland.

As shown in the maps and video below, the newly discovered fault networks are located to the north, south and southwest of Mt. Hood and extend to the Columbia River.

A 7.2 magnitude earthquake is larger than the 1989 earthquake near the San Francisco Bay Area.

Moreover, the faults on Mount Hood are closer to Portland that the epicenter of the 1989 earthquake was to San Francisco.

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Map of the new fault lines discovered to the North of Mount Hood extend to the Columbia River. Map via GSOC

This would be a crustal earthquake as opposed to the Cascadia subduction zone earthquake Portland has been bracing for.

Subduction zone quakes are deeper below the surface, they last longer — as long as seven minutes — but they are lower in amplitude.

The kind of quake we would get from Mt. Hood would be shorter — 20 seconds to less than a minute — and would be strong enough to knock you off your feet.

https://strangesounds.org