- In the Pacific Northwest, a slow motion collision of tectonic plates along the Cascadia subduction zone has been building tension for over 320 years.

And when that tension is released, the resulting earthquake is likely to be as large as a magnitude 9.

That will be 45 times more powerful than California's most destructive quake in 1906.

And the consequences defy imagination.

(building rumbling) This megathrust earthquake is predicted to be so significant locals simply call it The Big One.

And scientists estimate that it has an alarming 37% chance of occurring within the next 50 years.

In this episode, we'll learn just how this mega quake will impact our cities and find out what's being done to prepare our infrastructure and learn some invaluable lessons about how to make a plan for when The Big One hits.

(dramatic music) Subduction zone earthquakes often cause sudden movement and changes on the ocean floor, triggering tsunamis large enough to completely wipe coastal communities off the map.

Remember the Fukushima power plant disaster?

In 2011, Japan was hit by a magnitude 9 earthquake, similar to what we're anticipating here on the West Coast and it unleashed a tsunami of devastating proportions.

Chris Goldfinger is a geologist in Oregon who studies earthquakes and he happened to be in Japan when the quake hit.

I asked him to tell me about his experience.

- We went outside and just watched buildings moving, flagpoles whipping, and it just felt like the whole earth had turned to liquid.

Yet you could feel this grinding plate underneath us.

And as we watched it, though, we knew that Northeast Japan wasn't expected to have anything bigger than about an 8.4.

But when it hit three minutes and went past three minutes, we knew that was wrong.

They were going, this is a nine.

It has to be a nine.

That's what it takes, three minutes - [Maiya] Because of a long history of earthquakes, Japan was so well prepared that this mega quake destroyed a relatively small number of buildings.

But they just didn't expect the size of the tsunami that followed.

(tsunami siren howling) Allison Pyrch, an engineer from Oregon, visited in the aftermath.

- And it toppled most of their tsunami walls inundated huge amounts of the Japan coastline.

It killed 16,000 people.

And we were there six to eight weeks after the tsunami, going and standing there and smelling the fish smell.

And you can imagine where the water went 'cause you can see the water lines on the trees on the hills around it.

You can see the pieces of people's lives strewn around.

So as an Oregonian, that's really hard, knowing that that's what our coastline is gonna look like.

- And while the Tohoku quake in Japan was the costliest natural disaster in the world's history, here on the West Coast of the United States, we're nowhere near as prepared as Japan was for this kind of disaster.

- If that had been Cascadia and I'd been at work, my building would have collapsed.

There's no question about it.

I might've gotten out, it might not, but it would be gone.

Everybody thought Cascadia was A size, meaning no earthquakes, because historically, that's what it was.

It was dead silent.

And then the first evidence was discovered in the early to mid eighties, realized that we just happened to be sitting in a quiet spot.

- The Cascadia subduction zone is a 600 mile fault that runs from Northern California up to British Columbia.

Over the last 10,000 years, geologic records show that there have been 41 subduction quakes here, which averages out to about one every 250 years.

The last one came in the year 1700.

That's 321 years ago.

Since then, tension along the subduction zone has been slowly building as the Juan de Fuca plate steadily pushes into and under the North American plate.

The plate edge continues to gradually bend and buckle and one day, it'll release that tension causing up to five minutes of violent shaking and triggering an immense tsunami that could reach a hundred feet in some areas.

- If you were looking at a bird's eye view of Portland or Seattle, very soon after shaking started, bridges and other longer infrastructure are going to be warping and falling off their foundations.

You would see unreinforced masonry buildings start to collapse.

This is where 95% of Oregon and Southwest Washington's fuel is brought in and stored.

These tanks will deform, they'll spill.

Any type of spark or metal hitting each other could also start a fire.

The Cascadia subduction zone earthquake is gonna be one of the worst disasters America's ever seen.

- [Maiya] Officials in Portland, Oregon created this animation showing what they predict one of the busiest bridges in the Northwest will look like.

And it's not pretty.

(tense music) (earth rumbling) In the aftermath of the quake, survivors along the coastline and towns like Seaside, Oregon will have as little as 20 minutes to evacuate before the massive tsunami hits.

- In a place like Seaside, what we need to do is get from here up to the hills right back there.

It's a very straight path, it's not that far.

It's a very doable evacuation, but there's a problem here because there's no way to get there without crossing one of these bridges.

The bridges were built before plate tectonics, so we've got no retrofitting at all.

If these bridges go down, people trying to evacuate are gonna have a problem.

They're gonna have to swim the river and then continue evacuating up the hill.

- [Maiya] To get an idea of just how risky this situation is, Chris actually flew our camera person oversee Seaside in his acrobatic plane.

(engine sputters) - As we're flying over Seaside, we can see how low elevation the town is.

Ground doesn't really rise much until you get well on the other side of the highway.

Pretty much everything on the west side of Highway 101 is pretty likely to be inundated.

(ominous music) I mean, I came home from Japan feeling optimistic about it, but at the same time, I look around at the Pacific Northwest and I can see just visually that yeah, we are a thousand years behind and this is not gonna be easy to catch up.

- But officials in the Northwest are getting started.

Portland is currently reviewing options to build a new Burnside Bridge to serve as a lifeline after the quake.

And all new structures are being built up to earthquake standards.

Still, the vast majority of homes in the region are not ready for earthquakes of this magnitude, and aren't even bolted to their foundations.

Michael Wieber is a contractor specializing in retrofitting homes to make them more likely to survive an earthquake.

- So this house was built in 1911.

There really wasn't a building code back down.

This house is sitting on the foundation through the grace of gravity.

We're going to rectify that.

We're going to collect those earthquake loads and get them into the foundation to prevent the house from moving off the foundation.

So the vast majority of our work takes place underneath the house.

So in this case, the basement.

(soft guitar music) All right, so this is a special order plywood that's designed for earthquake loads, and it's going to install like this to get those loads from this beam up here into the sill plate down here.

And then we'll install this side plate and we'll continue that load path into the foundation.

(drill whirring) - The most important retrofit is strengthening the connection from the walls to the floors and to the foundation.

Some homes are simple to retrofit and it's possible to do it yourself, but others are very complicated, so it's worth having a professional take a look if you live in an earthquake-prone area.

And there's a lot you can do without construction skills, like making sure tall furniture, heavy wall decorations, appliances, and even electronics like televisions are securely attached to the wall, so they don't fall on people during a quake.

Mark Ginsburg is a Portland NET or neighborhood emergency team leader and has been preparing for The Big One for over a decade.

Despite living and breathing disaster preparedness, Mark, surprisingly doesn't seem too overwhelmed by the inevitable earthquake.

- It's not the thing that keeps me up at night because I know that I can't control it.

I understand where I live and I understand that that's a possible risk.

But I also know that if I do some preparedness work and if I do trainings, this year I redid my first aid and AED trainings.

Those are the parts that I can do and that I can control.

There's your house and the physical things, there's the knowledge, and there's a plan.

But I think having the things that you as a family or a household need to just be independent for a little while is really crucial.

- Here are Mark's top five most important things to keep in your home or garage when preparing for The Big One.

- Shelf stable food, water, one gallon per person per day.

Good fire extinguishers, the more the merrier.

Two bucket toilet.

Toilet seat, clips on the bucket.

Toilet paper.

Saw dust for your poop.

For in one gas shutoff tool.

Thank you.

Water shutoff in the bottom, gas shutoff on top.

If you turn off your gas, you leave it off and let the pros turn it back up.

- Shutting off your gas can be crucial to stopping fires.

If you smell gas in your home after an earthquake, Mark suggests grabbing your for in one tool and simply turning the valve to the off position.

It's easy to feel discouraged or overwhelmed when thinking about preparing for a disaster as large as The Big One, but I think we could all take a page out of Mark's book.

- The time to figure out what to do is not after the earthquake, the flood, the fire, but to know in advance, if those things happen, what should we do?

- You don't have to join a local emergency team, although it's great if you do, but just taking small steps today to start your preparation like picking up a gallon of water or a few extra cans of soup for your pantry can go a long way.

- People will want to help and will step up to help to the best of their abilities.

That's what everything shows will happen and what has happened in the past and we can expect that's what's gonna happen should we need it in Portland.

- And for a more detailed look on how you can prepare ahead of time for an earthquake or for any other disaster for that matter, check out our episode on how to stock your pantry and pack a go-bag.

Thanks for tuning into this episode of "Weathered" and as always, don't forget to like and subscribe so you never miss an episode.

See you guys next time.

(soft music)