Up next in 10
What If The Big Earthquake Hits The Pacific Northwest Tomorrow?
4K views
Mar 31, 2025
Off the coast of northern California, Oregon, Washington, and British Columbia sits the Cascadia Subduction Zone, a particular kind of fault line that will eventually unleash an earthquake not seen since the year 1700. When it does eventually hit, it's estimated to be the largest earthquake to ever strike the modern United States. Unfortunately, the Pacific Northwest has not prepared for such an incredibly devastating disaster. So what happens if it the big earthquake hits tomorrow?
View Video Transcript
0:00
Sitting off the coast of the Pacific Northwest is a ticking time bomb
0:03
The Cascadia subduction zone will eventually erupt into the biggest earthquake in modern history
0:08
and with it will come a level of disaster that the United States has never before experienced
0:13
Unfortunately, it also happens to be in a region that has not prepared for such a catastrophic event
0:19
So what if the Cascadia earthquake hits tomorrow? Hello and welcome to What If Geography, where we try and answer the great geographic what
0:31
if questions of the world. I'm your host, Jeff Gibson, and today we're talking about a topic that will literally
0:37
shake the United States to its core. I am, of course, talking about the Cascadia subduction zone that lies off the coast of
0:44
California, Oregon, Washington, and British Columbia. So bolt yourself to your foundation because it's going to be a bumpy ride
0:51
Most people in the United States know of only a single fault line, the San Andreas Fault
1:00
Line in California, and for good reason too. Every once in a while, the San Andreas Fault Line sends a little shake through the spine
1:06
of California, rattling people and, depending on its mood, causing upwards of billions of
1:11
dollars in damage. In 1994, a 6.7 magnitude earthquake struck Los Angeles causing somewhere between $13 billion
1:18
and $50 billion in property damage. This is in addition to 57 deaths and 9,000 injuries
1:25
It is still, to date, one of the costliest natural disasters in US history
1:30
But while the San Andreas Fault Line is much more active, it really pales in comparison to the Cascadia Subduction Zone Fault Line
1:36
that extends from Northern California to British Columbia. This is because the San Andreas Fault Line has an upper limit of how powerful it can get
1:42
Every fault line has an upper limit, and the San Andreas Fault Line caps off at about an 8.2 on the Richter scale
1:47
The Cascadia subduction zone earthquake can go to at least a 9.0, and potentially much higher
1:53
That might not seem too different, but because earthquakes are measured on a logarithmic scale
1:58
a full point higher can be many, many, many times more powerful. To put this in perspective, a magnitude 6.0 earthquake will typically only last a few seconds
2:07
a magnitude 7 earthquake for about 15 seconds, a magnitude 8 earthquake for about 2 minutes
2:13
and a magnitude 9 earthquake for at least 4 minutes. That 1994 earthquake that caused upwards of $50 billion in damages lasted somewhere between 10 and 20 seconds
2:23
The Cascadia subduction zone earthquake at a magnitude of 9.0 would shake for much longer
2:29
And the reason why the Cascadia subduction zone fault line is so much more powerful has to do with the way the two tectonic plates are meeting You see the Juan de Fuca plate is slowly sliding underneath the North American plate or at least it should be The reality is that the North American plate is kind of stuck
2:44
So the Juan de Fuca plate is continually trying to press under the North American plate. This is
2:48
creating a lot of built up pressure and energy in a similar manner as if you were to pull a rubber
2:53
band all the way back. At some point, that energy will snap and release itself, causing what is
2:58
likely to be one of the largest earthquakes in modern history. The last time this occurred was
3:03
on January 26th, 1700, and the earthquake is estimated at somewhere between an 8.7 and 9.2
3:09
magnitude. If we go back even further, we can see that there is typically an average cycle of about
3:13
500 years in between each earthquake. Today, we're at about 322 years into this cycle. This might make
3:20
you feel safe, but remember that averages are just that, averages. The earliest estimated gap was just
3:25
390 years. And there's nothing really that says it can't be sooner than that. In 2009, geologists
3:31
predicted a 10% to 14% probability that the next Cascadia subduction zone earthquake will produce
3:36
a magnitude 9.0 earthquake within the next 50 years. Those are not insignificant odds
3:42
Today, Oregon, Washington, and British Columbia are scrambling to prepare for the inevitable
3:47
Cascadia subduction zone earthquake. Prior to about 1980, there was no real idea to the dangers
3:53
that the region faced. As such, buildings and bridges were not built up to any sort of code
3:58
that would be able to withstand an earthquake. And unfortunately, they're all still very far
4:03
from being ready. But before we get into what would happen if the mega earthquake struck today
4:08
if you're enjoying this video, now would be a great time to subscribe. More fun geography videos are just one click away
4:14
The Cascadia of Subduction Zone lies somewhere around 50 to 100 miles off the coast of the
4:23
Pacific Northwest and runs about 620 miles from the northern part of California
4:28
all the way through Oregon and Washington, and ending off the coast of Vancouver Island
4:32
British Columbia. In theory, the big one could strike anywhere along this fault line
4:36
However, scientists at the California Institute of Technology have calculated that the southern
4:41
portion of the fault line is the most likely location where the next big earthquake will
4:44
strike. This would place the likely epicenter somewhere off the coast of Northern California
4:48
up to about Central Oregon. But regardless of where it hits along the fault line
4:53
the reality is that the entire region would feel it. Literally. At a minimum, the major cities of
4:58
Eugene, Portland, Tacoma, Seattle, Everett, Victoria, and Vancouver would all be impacted
5:04
in some way The Federal Emergency Management Agency is operating under the assumption that everything west of Interstate 5 will be completely destroyed All told it estimated that over 10 million people spread over nearly 100 square miles
5:17
will be directly impacted by the Cascadia subduction zone earthquake in some way
5:22
And depending on how close to the epicenter those people are, we'll determine just how impacted their life will be
5:27
Not only for the moment during the earthquake, but for many years after
5:31
When the earthquake does eventually hit, the first sign won't be an abrupt and continuous shaking
5:40
Instead, a compression wave will emanate out from the epicenter faster than the actual earthquake
5:44
itself, and while humans likely won't notice it, animals will. And in particular, dogs. So for about
5:51
90 seconds, a loud cacophony of barking will erupt throughout their region as they get wind of
5:56
something happening. But also, thanks to a newly installed early warning system for Oregon and
6:01
Washington, anyone with a mobile phone will likely get an alert as well. It may not seem like much
6:06
but those 90 seconds are enough time to automatically perform a variety of life-saving
6:10
functions, such as shutting down railways and power plants, opening elevators and firehouse doors
6:16
alerting hospitals to halt surgeries, and triggering alarms that the general public can take cover
6:22
Take a look around your home right now, and imagine that in 90 seconds everything is going
6:25
to come crumbling down, inside and out. Where would you go? Once the shaking does
6:31
actually begin, the power will almost immediately go out everywhere west of the Cascade mountain
6:35
range. From that point on, it will be roughly four minutes of violent shaking. Every window in your
6:41
home will shatter, creating an incredibly dangerous moment as razor sharp shards of glass literally
6:46
fly everywhere. And unless your home is bolted to its foundation, which it probably isn't
6:52
it's going to bounce around your neighborhood and smash into basically everything else bouncing
6:55
around the neighborhood. At the end of those four minutes, your surrounding neighborhood will scantily
7:00
look the same. It will be a level of devastation that few people have ever witnessed. But while
7:04
your neighborhood has been shaken to its core, many more are actually now underwater
7:13
Tsunamis are perhaps the most dangerous natural disaster humans have to endure
7:18
And because the Cascadia subduction zone will hit under the ocean, it's absolutely inevitable that
7:22
a tsunami will race out from the epicenter towards the west coast of the United States and Canada
7:27
Depending on the location, people will have somewhere between 10 minutes and 30 minutes
7:31
to get out. People will need to literally drop everything and run for the hills
7:37
Today, along the Pacific Northwest coast, there are about 71,000 people who live at an
7:42
elevation that would be demolished by the oncoming tsunami also known as the inundation zone While it been illegal to build hospitals schools and firehouses in the inundation zone since 1995 many still exist in
7:53
this area. In 2004, an earthquake-caused tsunami hit 14 countries in Asia and killed over 227,000
8:00
people. While there are fewer people living within the Pacific Northwest inundation zone
8:04
the level of death and destruction will likely be staggeringly high. When the shaking stops and the tsunami recedes, the damage to the region will become clear
8:17
Coastal communities simply won't exist anymore and the major cities of the region
8:21
mostly Portland and Seattle, will be a crumpled shell of their former selves
8:25
For those that survive, they now have to live with the aftermath of such a disaster
8:29
And it won't be easy. Currently, it's estimated that along the I-5 corridor, which includes Eugene, Portland
8:36
Tacoma, Seattle, and Everett, it will take between one and three months after the earthquake to
8:41
restore electricity, a month to a year to restore drinking water and sewer service
8:46
six months to a year to restore major highways, and 18 months to restore healthcare facilities
8:52
On the coast, you can basically double all those numbers. And of course, those estimates do not
8:57
even apply to the tsunami zone, which will basically be uninhabitable for years. The entire
9:02
region of the Pacific Northwest will never be the same after the big earthquake. And while the
9:06
federal government will likely pay for the entirety of the costs to rebuild, the damage to the Pacific
9:11
Northwest economy will take a generation to rebuild. A large part of the population will leave and
9:15
simply never return. Major companies and businesses such as Microsoft, Amazon, Nike, Intel, Boeing, and
9:21
many more large economic engines for the region will relocate to other parts of the country and
9:26
again, probably never return in any meaningful capacity. The Pacific Northwest, for all its majesty and natural beauty
9:33
will turn into a bit of a ghost town and it will be a very, very long time
9:37
before it returns to any sense of normalcy. In all of this, the good news is that the Pacific Northwest
9:43
still has time to prepare. In fact, the region could have 100 years or more
9:48
Today, both Oregon and Washington have taken a lot of steps to prepare for this inevitable earthquake
9:53
In 2014, Portland had zero bridges that would survive the earthquake. Today, it has two lifeline bridges, and more are being planned and built as you watch this video
10:03
That's incredibly important progress. I hope you enjoyed learning about the Cascadia Subduction Zone earthquake
10:09
If you did, please subscribe to my channel. And if you want to watch more of my What If Geography videos, you can do so right here
10:17
Thanks for watching. See you next time
#education