Public opinion on the mega-tsunami threat from the Cascadia Subduction Zone is largely mixed with prevalent anxiety and skepticism. Many are concerned about the potential devastation, questioning the reliability of predictions and the adequacy of preparedness measures by local authorities. While some express fatalism and a lack of trust in predictive models, others share resources and strategies to enhance personal readiness.

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Emergency Preparedness Organizations

this video is brimming with misinformation.  It's like some dude at a party explaining what his friend told him about that 2015 New Yorker article. 


 A large cascadia event would actually cause a pretty small tsunami in Seattle.  The change in ground level here would be low compared to places along the coast, and the wave has to travel all the way through the Sound to get here.  


 The DNR publishes maps for expected flooding under different earthquake scenarios:    
https://www.dnr.wa.gov/programs-and-services/geology/geologic-hazards/tsunamis#tsunami-hazard-maps

conus_coffeae

My free-to-access (no sales, subscriptions, membership dues, just free info) website offers Cascadia-specific information compiled from reputable field experts. The site has 36 pages, but I’ve listed a few below that may be of interest. While the site is a personal endeavor, I work in the Emergency Management field and often come across resources and information that I enjoy sharing. Feedback is always welcome.

 

Tsunamis: [https://survivingcascadia.com/the-power-of-sister-tsunamis/](https://survivingcascadia.com/the-power-of-sister-tsunamis/)

Megathrust Earthquakes: [https://survivingcascadia.com/megathrust\_earthquakes/](https://survivingcascadia.com/megathrust_earthquakes/)

Likelihood of an 8.0: [https://survivingcascadia.com/37-in-50-years/](https://survivingcascadia.com/37-in-50-years/)

Estimated Impacts: Regional: [https://survivingcascadia.com/estimated-impacts-regional/](https://survivingcascadia.com/estimated-impacts-regional/)

Co-occurring and Cascading Hazards: [https://survivingcascadia.com/worst-case-scenario/](https://survivingcascadia.com/worst-case-scenario/)

Cascadia’s Impact Area: [https://survivingcascadia.com/part-1-cascadias-impact-area/](https://survivingcascadia.com/part-1-cascadias-impact-area/)

SurvivingCascadia

wantonwontontauntaun

I’m just glad this area doesn’t have anything like the Hayward Fault which has been eerily quiet for a long time and goes straight through the cities.

SuperMike100

This would be a wonderful sequel to San Andreas

Sprinkle_Puff

That seismic zone seems to have a capacity for the largest most violent quakes humanity has ever known in recorded history. 

We’ve got Tōhoku, Sumatra, Chile, and Alaska as the big boys in the last 100 years. Tōhoku was very ready for quakes and tsunamis and they lost 20k people. The Pacific Northwest is not ready. They are dancing with the devil saving tax dollars on disaster preparedness just hoping that it’s not their generation that gets the bad dice roll.

bunkerbash

I live in Southwestern Canada which happens to be in the Cascadia Subduction Zone.

We have been warned that some day the Cascadia Subduction Zone faultline will someday snap resulting in a magnitude 8 or 9 megathrust earthquake and tsunami.

Sadly it will be the worst natural disaster in both Canadian and American history with massive damage, loss of life and injuries and it will take years for a full recovery.

I always wish that it will never happen but sadly it is going to happen sometime in the future.

Apprehensive_Idea758

*Great Earthquakes of the Pacific Northwest*    
https://youtu.be/UJ7Qc3bsxjI     

**50 Year Probabilities**    
Cascadia Trench Full Rip 9.0:   14%        
Cascadia Trench Partial Rip 8.0:   25-40%    
Seattle Fault:   5%        
Puget Sound Shallow Fault 7.0:   15%       
Puget Sound Deep Fault 7.0:   84%

holmgangCore

Lots of good info here:  r/CascadianPreppers/

attorneyatslaw

[I read this a few years ago.](https://www.newyorker.com/magazine/2015/07/20/the-really-big-one)

I think I won't be moving out west anytime soon.

booksgamesandstuff

Good site. You might add info on strengthening homes ([bracing &amp; bolting](https://www.earthquakebracebolt.com/)) and also securing things inside the home, like [water heaters](https://www.earthquakecountry.org/step1/waterheater/).

Cherimoose

I spent 20 years on the southern Oregon coast where the fault is closest to the shore. Everybody who lives there has some kind of plan what they will do. But the hard reality is you can't really prepare for a mega-quake.

And if it happens at night, most everyone along the coast is going to die... It will scour the ground right down to bedrock. You can't run during a big quake. You can't drive either. The roads will buckle. Rock fall will block the rest. And subsidence that occurs during the quake may bring the water in even before the tsunami forms... I know places where the land sank 30 feet in 1700.

Japan has the same offshore mechanics but in reverse. And, their fault erupts more regularly than the Cascadia fault. Therefore, more accumulated strain it has, the more dangerous it becomes.

When Cascadia lets go, it's going to be "biblical"...

[deleted]

If a volcano eruption happens first then ya something might happen

Far_Out_6and_2

I expect there to be as much shaking footage and tsunami footage if maybe not more than the Great East Japan Earthquake on March 11, 2011 if the Cascadia megathrust is to happen this decade.

probium326

It’s a good reminder. Go get a pallet of water, first aid kit, emergency radio. Along with food for a week, 3 days of it in a bug out bag and you’re more prepared than most.

Honestly, it’s little emergencies we should worry about most. Keeping a wool blanket, bit of food and water in your car and a flashlight would be a lot more likely to get used than earthquake prep

BrightAd306

I used to live on 40th Street and 8th Ave, in the U-District. Two blocks east of I-5. 

I woulda survived!

MeaningNo860

I live in an area near Seattle where we get a few power outages each year.  They may be a few hours, and a couple of years ago one was about 3 days. The number of people prepared for even those short outages is sad.

Sufficient-Wolf-1818

Fortunately that isn’t how earthquakes work. The whole “overdue” thing is a way over simplification, earthquakes aren’t predictable like that. It’s based off of the distance between past earthquakes, the problem being, earthquakes don’t follow patterns. Especially since the factors that cause earthquakes have changed a great deal since the last big one. People who tell you an earthquake is “overdue” have no idea what they’re talking about and shouldn’t be taken seriously. Btw the “due date” is a window of about 1000 years.

mooshroom333

No. Because a natural disaster doesn’t suddenly become more likely just because an unrelated one happened.

It’s been looming for decades and decades

CascadesandtheSound

As someone with extensive emergency management experience, and access to all the fun documents and studies (everyone does, they're all public information, just a little easier for me because it's need-to-know info), the projections for a worst-case cascadia subduction zone event pretty much leave most of the Seattle metro area in shambles. Most major cities not inhabitable for over 6 months if not closer to a year, and expected death toll in the 10s of thousands. There's also an expected PERMANENT  loss of population. People who move away and never come back - and up to a decade before life returns to 'normal'...

The most recent relevant documentation is here..  [https://mil.wa.gov/asset/62bc6bf87b6dc](https://mil.wa.gov/asset/62bc6bf87b6dc)

Plan is to evacuate Seattle across the sound to the Olympic Peninsula and stage rescue/recovery efforts from there. Most bridges will be damaged and impassable, and large areas will be 'helicopter only' access, where downed power lines, and debris don't block them from landing.

You will be on your own, for most of such event, and weeks after. No police. No fire. No groceries. No sewage. No water. You're gonna go back to the stone age.

While the initial death toll from the event itself is said to be relatively low, quite a few more will die in the aftermath due to lack of medical care, food, water, and sanitation, not to mention things like fire..  The vulnerable (elderly) populations being hit the hardest, of course.

You need to make alternate plans to get home, or to somewhere other than home, if you have a bridge between your house and your work - it won't be there or will be structurally unsound.

You NEED to have your preps on you. A 'get home' kit should be with you everywhere you go. 3 days of food/water, small tools, pry bar, emergency blanket, changes of clothes that match the season, respirator/mask, etc will all fit into a small backpack. In the event you can't make it home, you need to have an alternate plan of somewhere to go. You need to have a plan with your family.

Phones will be down, and there will be virtually no means of communication outside of satphones, starlink, and 2 way radio (amateur, GMRS, etc). The current radio system in use by King County will go offline, leaving only very limited range for responders in the field, who will be worried about their own families - it happens..

This is a 'prepared to be on your own for weeks, if not months' thing.. Not a 'Power went out for 2 days' thing.

Stockpiling water, dried goods, canned goods, etc is super easy.

For people in the Seattle area, LDS runs a storehouse in Kent that's all for long term food storage. They have the lowest prices in the area, much cheaper than other places ( even online), and you don't have to be a member of the church to shop there.

You can fashion a toilet out of a 5 gallon home depot bucket, and a trash bag. Even better if you buy a HUGE bag of pine shavings, like hamster bedding - it's an impromptu composting toilet. I had to daily use one for a while and a single bag (poo, wipe, toss shavings over it, repeat) lasts about 2 weeks. The bedding absorbs moisture and odors, and keeps things contained. When full you dig a hole and pull the bag out and bury it. This is for SOLID WASTE ONLY. Do no do #1 in your poo bucket. Go piss against a tree or a pop a squat (for the ladies). You do not want to mix liquid with this or it'll turn into sewage and become a smelly bacteria infested pit.

OldBayAllTheThings

HighColonic

  
Estimated impacts include the following:

● Earthquake

o Building damage – 618,599 buildings with moderate to complete damage

o Schools – 2,026 schools with moderate to complete damage

o Hospitals – 100 hospitals with moderate to complete damage

o Critical facilities – 2,777 critical facilities with moderate to complete damage

o Total economic losses – $134 billion

o Utility system economic losses – $15.9 billion

o Transportation system economic losses – $3 billion

o Job/wage losses – $6.2 billion



● Tsunami

o 27 counties, including areas impacted along the Pacific Coast, Puget Sound, and

Columbia River

o At least 17 tribal nations impacted

o 453 miles of impacted Pacific Ocean coastline (296 miles in Oregon, 157 miles in

Washington)

o 1,810 miles of impacted Puget Sound coastline, including the San Juan Islands

o 10- to 30-minute warning for coastal areas

o 90- to 120- minute warning for Puget Sound areas

o All seaports on the Pacific coast at risk of sustaining complete damage; seaports

along Puget Sound and the Columbia River (west of the I-205 bridge) at risk for

major damage

o Multiple tsunamis 10 to 12 hours after initial earthquake; first wave may not be

the largest

o Wave heights that vary from 3 to 80 feet

o Aftershocks of M7.0 or greater that could generate additional tsunamis  


The most recent relevant documentation is here..  [https://mil.wa.gov/asset/62bc6bf87b6dc](https://mil.wa.gov/asset/62bc6bf87b6dc)

SchufAloof

If it happens when Trump is President, we won’t even get aide in places that didn’t vote for him, something to keep in mind.

PleasantWay7

Nope, don't care at all. If it happens, it happens. There are no preparations to be made for a +9 magnitude quake.

liannawild

What is the point of this post? To state your anxiety?

SpicyArms

Chief_Kief

It will suck yeah, but we will be togetherness. All feeling the same shaking suckyness. It’ll be a time for community that we haven’t seen in decades

Literally yes! I was thinking that this week. So sad for NC.

gypsygeorgia

Yes! When I worry and stress about the earthquake I noticed that I keep us all safe one more day.

herpaderp_maplesyrup

skysetter

[https://youtu.be/ygH4hYfE9mg?si=3eQjCr5SreNak4nn](https://youtu.be/ygH4hYfE9mg?si=3eQjCr5SreNak4nn)

The 9.0 simulator on youtube......

Significant-Repair42

I live about 3/4 mile east of I-5 in the south sound… guess I’m good! Bet seriously, yes it stresses me out.

TempoMortigi

I think of anything above 33% a certainty to occur.

It’s a nice presentation, but you ask:

“What if we realize Cascadia is actually a high-probability/high-consequence hazard?“

Is this not already common knowledge? San Francisco, Los Angeles, Tokyo, Seattle/Vancouver are all places that I’m familiar with that have significant seismic preparedness planning and regulations in place, and hazard awareness and discussion are part of the culture. 

Is this not your experience in Cascadia?

MillerCreek

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So what's it all mean?

In the Cascadia Subduction Zone, which extends from Vancouver Island down to Oregon, scientists have long anticipated the potential for a massive earthquake. This would originate along the megathrust fault, a deep, continuous fault where the oceanic lithosphere is slowly being forced beneath (subducted) the North American plate. This primary fault is well-documented, geologically active, and represents a serious seismic hazard. Researchers have also proposed the existence of a proximal, secondary structure... the megasplay fault.

The megasplay fault, as previously proposed, is a large, steeply dipping thrust fault that branches off the megathrust at depth and cuts up through the accretionary wedge (the stack of sediments scraped off the downgoing plate). It was thought to align with a significant geological boundary in the wedge where rock types and strengths change, known as the Inner-Outer Wedge Transition Zone, or IOWTZ.

The concern is if a megasplay fault exists and ruptures during a major earthquake, it could produce more rapid and focused vertical movement of the seafloor, which in turn could generate a much larger and faster-arriving tsunami than the megathrust fault alone. Because of this potential, the megasplay fault has been routinely included in tsunami hazard models used for emergency planning in the Pacific Northwest.

This research shows, however, that there is no strong evidence of a continuous, active megasplay fault system running from Vancouver Island to Oregon, as was previously assumed. 

- In some regions, there are short segments of faulting that may resemble splay faults, but these are discontinuous, often inactive, and in many areas entirely absent.

- The wedge structure is highly variable along strike, meaning that each segment of the margin behaves a little differently.

- The IOWTZ, where a megasplay fault was most likely expected to occur, does not host a fault system that is consistently active or coherent.

Importantly, this does not change the fundamental earthquake risk in Cascadia. The megathrust fault is still present, still active, and still capable of producing a magnitude 8 to 9 earthquake with significant ground shaking and tsunamigenic potential. However, what this new work suggests is that the tsunami hazard associated with rupture onto a megasplay fault may have been overestimated in some scenarios.

GeoGeoGeoGeo

Studies warn of mega-tsunami risk from a potential earthquake along the Cascadia Subduction Zone, threatening the US West Coast with unprecedented impacts on infrastructure.

Cascadia Subduction Zone Mega-Tsunami Threat

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