Weathered

- Unlike hurricanes, tornadoes, or wildfire.

Large subduction zone earthquakes are rare, but they have the potential to cause catastrophic damage and produce massive tsunamis that can travel the speed of a 737, that's over 500 miles per hour.

And these tsunamis aren't something you can just ride out.

- Normal ocean waves are produced by wind.

It's almost like you have your coffee cup, it's too hot and you just blow on it and you create waves on the surface.

But now let's suppose that you put down your coffee cup abruptly.

Then what you do is you create the tsunami tsunamis.

They're generated by a displacement of the ocean floor.

They move the entire ocean column up.

I mean, the wavelength is of the order of several miles.

- And another thing that's particularly scary about tsunamis, so - You have this mountain of water that's coming in, slows down, slows down, slows down.

You sit there looking at it, and suddenly it hits the soul line.

The tsunami accelerates when it hits, you know, the dry beach.

- Every coastline around the world is at risk of tsunamis, but some areas are particularly prone and they can be deadly.

In 2004, a magnitude 9.1 earthquake off the coast of Sumatra spawned the deadliest tsunami in modern history, reaching as high as 100 feet and killing more than 230,000 people in the west coast of North America is overdue for a subduction zone earthquake, the Cascadia megaquake, which could produce a series of deadly tsunamis.

And here we didn't start planning for tsunamis until well after we created our whole modern built environment.

So there are just a lot of places where there isn't anywhere to evacuate to.

So we wanted to know how can you survive a tsunami and what do you do if there's no high ground?

- There are several communities where the time it takes to walk is far greater than the estimated wave arrival - Time.

It's a known loss of life.

- Unless we change our course.

The death toll from the Cascadia subduction zone earthquake and tsunami will almost certainly surpass any other natural disaster in US history.

So keep watching to find out what the number one factor is that determines the difference between life and death.

Tsunamis can be caused by landslides, volcanic eruptions, even meteor impacts, but they're most commonly caused by earthquakes.

And the biggest are caused by subduction zone or mega thrust earthquakes.

These are earthquakes which occur along fault lines between tectonic plates.

- It took us a long time to understand why these big earthquakes were happening, where they were happening.

The knowledge of plate tectonics is surprisingly recent.

That really became a formally accepted theory in the sixties.

The earth is made out of these broken up plates, these shells of crust that are floating, and then sometimes they crash into each other.

And when they crash into each other, that's a subduction zone.

When Earth formed, it was really, really hot.

You know, four and a half billion years later, it's still cooling the tectonic plates at the top.

They're the coldest part of the earth 'cause they're the outside rind planet, but the inside is still warm.

So what ends up happening is the plates, as they cool, they begin to sink back into the earth.

And new warmer materials sort of bubbles up to the surface.

It's like a spherical lava land where there's blobs coming up and then blobs going down just at really, really slow speeds.

It's about an inch, two inches per year, - And that's about the speed that your fingernails grow.

- So even though the plates are moving where they touch, they tend to get stuck just because of friction.

It's like sandpaper.

And so yes, there's an inch of movement every year, but for three or 400 years, the plates remain stuck at their contact, which means there's three or 400 inches of movement that were accumulating over the decades and centuries.

And eventually the rocks can't take it anymore.

And when they give way, those 300 inches move.

And that's the earthquake itself.

And that's what creates the really strong shaking that damages buildings.

That's what creates the tsunami.

That's what wreaks havoc.

- And these seduction zones are found all over the world.

More than 80% of all tsunamis happened in the Pacific Ocean along what's known as the ring of fire and the Cascadia subduction zone along the west coast of the US has gotten a lot of attention in recent years because scientists only recently figured out that it too is capable of producing massive earthquakes and tsunamis.

- In the eighties and nineties, scientists started digging in and looking for past tsunami deposits and evidence of past earthquakes, and they found evidence of drowned forests or ghost forests that indicated that the land had suddenly changed.

And then they discovered they could date some of the tree rings from these drowned forests and trees.

- In Cascadia, we know January 26th, 1700 there was at least a magnitude 8.7, most likely something like a magnitude nine.

And that produced a very big tsunami that you can see today.

If you go and scrape around in the rocks, you can actually put your finger on sand deposits from the tsunami here at location on Red Coast.

And it's in historical records in in Japan.

- That's right.

The tsunami that was triggered by the cascadian mega quake did massive damage all the way across the ocean.

In Japan, - They called it the orphan tsunami 'cause they didn't feel the earthquake and so they weren't sure where it came from.

- And now city officials and disaster planning experts all across the west coast are planning for the next one.

Scientists predict that there's a one in three chance of at least a partial rupture happening within the next 50 years.

We actually have two videos on this earthquake, which we'll link below.

But here's a quick description of what it'll feel like when it happens - For Cascadia.

We expect for one of these full margin ruptures that the shaking could last three to six minutes.

If you feel earthquake shaking for a very long period of time, that's one of your clues that a Cascadia earthquake has happened and that a tsunami is coming.

- So when the tsunami starts, it propagates in both directions.

The speed of a tsunami depends on the depth of the ocean.

The deeper the ocean, the faster the that the tsunami travels, the the shallower, the the ocean, the the tsunami slows down.

But - After combing through amateur video, the 2004 tsunami in the Indian Ocean, scientists notice something unusual while the tsunami slows down.

As it climbs the sloping beach, it actually accelerates just after hitting the shoreline.

This can give onlookers an artificial sense of security before inundating the area.

- The tsunami, most of the time looks like a faster seeding tide.

People are not - Prepared, and it's not just one wave.

- Tsunami waves don't just come once they come in a series of waves and they are kind of like sloshes in a bathtub.

They can get bigger with each incoming wave.

- If you've seen footage of storm surge in hurricanes, it's looks a little bit more like that, where the water just starts rising and keeps rising and keeps rising and keeps rising.

- And with nothing in its way.

It can travel many, many miles inland in Washington state.

It's modeled to travel through the Strait of Juan de Fuca down into the Puget Sound.

- That means in the event of a Cascadia Megaquake, even cities like Seattle and Portland will likely be impacted by the tsunamis.

So what's the one factor that determines if you live or die reaction time?

- The first variable that determines survival rates is how quickly you move out of harm's way.

- Early warning systems can be helpful, especially for tsunamis that are generated from a distant earthquake where you won't feel the shaking.

But for a local subduction zone event, even the best early warning systems may not give you enough time.

- Using a combination of GPS and seismic stations, we measure the earthquake, then we can say, okay, the earthquake is about this long, it has about this magnitude.

And so we can make a crude guess that that's gonna make a tsunami of about that size.

And we can typically do that in the first five minutes after an earthquake.

- But in the Pacific Northwest, there are places where the tsunami may hit in as little as 10 to 15 minutes after the quake.

So you can't afford to wait around for those five minutes when every moment counts.

What do you do?

- In all reality, if you feel an earthquake and you're near the coast or a body of water, that is your warning that a tsunami may come and you should evacuate to high ground immediately.

- But that's easier said than done.

- You need to know where safety is, and that's not immediately obvious.

- You need to be able to react fast.

And that means already having a plan in place before the earthquake hits.

You should know where high ground is, what's high enough, and how you're gonna get there.

And perhaps most importantly, you should practice.

And there are helpful tools with this tsunami evacuation zone map, which we'll link in the description.

You can input the address of your home or where you're vacationing, and it'll tell you where you need to go to get to high ground and how long it'll take for you to walk there.

But there are some places where there is no high ground for miles.

Long Beach, Washington is particularly vulnerable.

Its entire population and all of its businesses are within the inundation zone.

And there are communities in Oregon and California and the same situation.

- Those are really precarious locations.

You'd have to run at Usain Bolt speeds for 40 minutes sustained to be able to get outta the way.

That's just not going to happen.

That's - Where vertical evacuation structures come in.

But we've built shockingly few of them, just three in the US in fact.

And one of them is the Hatfield Marine Science Center in South Beach, Oregon.

- It actually sits on a hundred foot foundation.

It is tied to that foundation with 50 foot leg bolts to make sure that the building and the foundation stay together during the shaking.

And then when the tsunami wave hits the building, the walls of the building are designed to fall off, and that will allow the water to move through the building.

While we are safe.

On top of the roof, we have a cache of supplies that will take care of the nearly 1000 people that are expected to take refuge on top of the roof, - And they're expecting to stay on top of the roof for up to two days until the water leaves and it's safe to come down.

- I make models of tsunamis.

This is my job.

I will go and enjoy the beach and I will just, you know, point the car in the right direction and make sure I'm aware of where a hundred feet is.

And I'll look at Google Maps at the topography and make a little plan in my head of what I would do, you know, collect the dog and go that way.

- Those people that recognized the signs and moved immediately away, they were saved.

- There's still a lot that needs to be done to prepare communities for this inevitable tsunami.

We need more vertical evacuation structures, more signage and more outreach.

- Let's not be scared.

Let's take charge of the situation.

Science and technology are awesome.

If we get together and do the work, the consequences might be a lot less than if we just stick our head in the sand and pretend like la, la, la, la, la.

I can't hear anything.

That's a lot worse.

Inaction is the worst decision.

- That's pretty profound, isn't it?

Not only might humans benefit from embracing the sentiment in regards to the inevitable Cascadia subduction zone, mega quake and tsunami.

Perhaps this is a sentiment that humans would benefit from in general as we continue to experience natural disasters in ways like never before.

Ignorance is bliss, but is it best?

As I digress, if you're in an area at risk of a tsunami and you'd like to do what Dr. Melgar said and take charge of your situation, here are some things that you can do.

First, be sure to know ahead of time where high ground or safety is.

Map out and practice your evacuation.

Prepare a go bag with essentials.

Know the signs of a tsunami, be sure to prepare.

Stay safe and see you next time.