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0:02
(rumbling) (car alarm) ♪ ♪ NARRATOR: Seattle and Portland lie in ruins. The devastation spreads 600 miles along the Pacific coast. Rivers burn. 45,000 injured or dead.
0:27
CHRIS GOLDFINGER: This is a big problem. And we're living inside the time bomb. WILLIE NUNN: Bridges, at least half will be collapsed or damaged. The police department, half of those. The hospitals, two thirds devastated. NARRATOR: Entire towns swept away. It could take decades to rebuild. NUNN: We're going to have blackouts for months at a time. We're looking at years of recovery.
0:58
(glass shattering) NARRATOR: This disaster hasn't struck yet, but it will. GOLDFINGER: We're in a race, and it's a race that we're going to lose. NARRATOR: What will trigger the catastrophe? Now using the latest scientific data, we can peer deep inside our planet to reveal the mounting danger right under our feet. HAROLD TOBIN: It's going to be the most devastating event that's ever taken place in North America. ♪ ♪ ♪ ♪ ♪ ♪ NARRATOR: Low tide reveals the first clues
1:46
to the fate of the Pacific Northwest. GOLDFINGER: Tree stumps in the beach, kind of an odd thing. Can see the whole beach is covered with these things. There's probably, looks like a couple hundred of them. NARRATOR: Beneath the sand, our x-ray shows these stumps were once a mighty forest. GOLDFINGER: It's pretty amazing. They're western red cedars that don't rot. I'm lucky to have this job. It's great. (chuckles) NARRATOR: This is just one of dozens of sites along the coast.
2:25
GOLDFINGER: To actually see this stuff and see the scale of it, and realize that this has happened all up and down the coast for a thousand kilometers, this is big stuff. NARRATOR: And a big mystery. GOLDFINGER: They really have a low tolerance for salt water, so they really shouldn't be anywhere near here. If we dig into this a little bit more, we might learn something important. NARRATOR: Something that could save thousands of lives from a natural disaster.
2:59
Neskowin Beach sits at the heart of the Pacific Northwest.
3:05
An emerald blanket stretching across three states. Home to millions, many of whom live in two of the region's most important cities. Meccas of technology and innovation coupled with historic beauty and culture: Portland and Seattle.
3:30
ERIN WIRTH: I love it! I think there's a great quality of life. There's a lot to do out here outdoors, and it's a beautiful city.
3:39
DOUG TOOMEY: It's an area with beautiful mountains, beautiful ocean. From a geologist's point of view, it's a wonderland. TOBIN: We have the mountains, we have the sea, we have kind of all of the hills and all of the beautiful topography of Cascadia.
3:57
I wouldn't choose to live anywhere else.
4:03
NARRATOR: But each scientist knows the region's stunning beauty masks a deadly threat.
4:12
Nearly 150 miles north of Neskowin, in the salty water of the Copalis River, geologist Dr. Carrie Garrison-Laney searches for clues. ♪ ♪ CARRIE GARRISON-LANEY: I do love digging in the mud. And a friend of mine I hadn't seen in 30 years said, "Oh, you did end up digging ditches after all." (laughs) NARRATOR: To Dr. Garrison-Laney, this mud is a time machine. Locked away in its past: more freshwater trees. GARRISON-LANEY: What we're looking at here are roots from the Sitka spruce.
4:53
The trunks have long since rotted away, but the roots have persisted because all of this mud closed in on top of them. It looks pretty innocuous, but this is definitely a murder scene.
5:12
This was a forest. We would have seen very tall trees. This area would have been much higher. So, what we can tell is that the land level dropped by at least this much.
5:30
NARRATOR: Sites like this are found along this coast from northern California to Vancouver Island, where the land plunged by up to 36 feet. GARRISON-LANEY: What you're looking at is the evidence of a large-scale disaster.
5:49
NARRATOR: The widespread destruction suggests the work of one force. GARRISON-LANEY: This is a very compelling package of land level drop like we see in subduction zone earthquakes.
6:03
And the greater the amount of subsidence, the greater the earthquake. (rumbling)
6:15
NARRATOR: South of the Copalis, the land around Neskowin collapsed to sea level, and the freshwater trees perished. The force that unleashed that titanic earthquake lies deep beneath the geologists' feet.
6:31
Using data collected from a vast array of sensors buried across the Pacific Northwest, we can now x-ray the earth to reveal what caused the devastation.
6:45
As the North American continent pushes westward, the x-ray shows it grinds atop the Pacific floor. ♪ ♪ ♪ ♪ Geologists call the fault line where the plates meet a subduction zone. Right now these trillion-ton slabs are locked in place.
7:12
When they slip: earthquake. At 620 miles, Cascadia is one of the longest unbroken faults on the planet.
7:28
The millions who live here could be hit by one of the deadliest types of earthquake: a megathrust. GOLDFINGER: It's hard to visualize how much power that is, but it dwarfs the largest atomic explosions by, by a lot! ♪ ♪ ♪ ♪ NARRATOR: The modern cities of Portland and Seattle have never seen a megathrust.
8:01
GOLDFINGER: If you go to Japan or Chile, it's hard to go a week without feeling some sort of earthquake. But in Cascadia, I've been here since the 1980s, and I have, I felt one.
8:17
TOBIN: It's unlike every other subduction zone in the world. There just haven't been any significant sized earthquakes at all. ♪ ♪
8:32
NARRATOR: Back on the Copalis River, Dr. Garrison-Laney finds another eerie clue.
8:40
GARRISON-LANEY: It's a really spectacular collection of dead trees, known as the Ghost Forest.
8:48
In the past we would have been in a very dense spruce and cedar forest, and then the ground level lowered. And within a few minutes, the tide water rushed in.
9:02
So that would have killed these trees very soon afterwards. NARRATOR: Just like at Neskowin Beach, except here whole trees remain, making it possible to date them. GARRISON-LANEY: Tree ring patterns are very unique. And we're able to show that the last ring that was put on, was the same year in all the same trees, the year 1699.
9:35
NARRATOR: Late that year or early 1700, a huge earthquake dropped the land across tens of thousands of square miles of the Pacific Northwest. Based on the vast area affected, geologists calculate the quake was as large as a magnitude 9.2, nearly 30 times more powerful than the 1906 quake that leveled much of San Francisco.
10:04
In the last 350 years, only six quakes this big have shook the earth.
10:15
Despite its deceptive serenity, the Cascadia fault is a card-carrying member of this infamous list. GARRISON-LANEY: It's a beautiful place to work, there's lots of amazing nature around, but we need to remember the message that Earth's telling us. NARRATOR: For more than 300 years, the Cascadia fault has been virtually silent. GOLDFINGER: This is a big problem. As geologists, we're fascinated about the processes and all that stuff, but many of us live here as well.
10:48
And we're living in the middle of this, like, inside the time bomb.
10:59
NARRATOR: When you're sitting on a geologic time bomb, one question hounds you: Could the bomb go off?
11:09
GOLDFINGER: It is ominous that it's so quiet.
11:15
What are the chances that this is the only aseismic subduction zone in world? NARRATOR: So is the Cascadia fault dead, or could it slip catastrophically again? Especially considering the neighborhood.
11:31
The Pacific Northwest sits on the notorious Ring of Fire: a cauldron of seismic plates and simmering volcanoes ringing the Pacific Ocean. GOLDFINGER: If you go around from Alaska and Japan and the Philippines, you've got a dozen or more subduction zones all active at the same time. NARRATOR: It generates 90% of the world's earthquakes. TOOMEY: And those earthquakes can be very damaging as we've seen throughout the Pacific Rim area. NARRATOR: Japan. New Zealand. California.
12:07
Everywhere on the Ring of Fire, the earth's tectonic plates grate on each other. As they bend and buckle, they store up energy like a spring. When the plates slip, they release all that energy.
12:25
Portland and Seattle straddle a 600-mile-long no-man's-land, where the Pacific and North American plates meet. The question is, what are the plates doing?
12:46
The fate of millions is stored in an array of simple GPS stations. Professor Goldfinger has spent more than 20 years analyzing the data. GOLDFINGER: There used to be just 5 or 6 stations. Then once we got a few stations like that, then more is always better, and you start infilling with as many as possible.
13:08
NARRATOR: The GPS coordinates from these stations tell Professor Goldfinger if the plates are stationary or moving. GOLDFINGER: If you have a subduction zone like this, and you put a GPS station on the land like this, if it's not locked, you would expect no motion relative to the interior. But if it is locked, then stations should show that they're being pushed inland. The first GPS stations pretty clearly and quickly showed that all of the leading edge of North America
13:33
was moving to the east. NARRATOR: Pushed by the Pacific plate.
13:40
All along the fault line, the two plates are quietly locked together. A bizarre oddity in the Ring of Fire. What force is so powerful to jam the plates together? ♪ ♪ ♪ ♪ An array of over 1,100 sensors, on land and off the coast, generate an x-ray of the earth.
14:15
More than 150 miles beneath the Pacific floor is a sea of semi-molten rock: the earth's upper mantle. The x-ray reveals two huge anomalies, each about 125 miles wide.
14:34
Super-heated rock rising from deep within the earth, called plumes. As they rise, they push up the Pacific floor, forcing it into North America, and jamming the two plates together.
14:55
Geophysicist Doug Toomey walks right on top of the southern mantle plume. TOOMEY: The megathrust is a couple of kilometers below us here at this point. If you were to strip away the oceans and look at the sea floor, you would see hot spot tracks in the northeast Pacific. And those hot spot tracks are mini plumes of hot, partially molten rock that's rising upwards. NARRATOR: The rock in the plume is hotter, so it's more buoyant. TOOMEY: So you can think of it as a balloon or something
15:27
that's lower density that wants to rise up and push beneath that subducting plate.
15:35
NARRATOR: Simple kitchen physics shows how the plumes lock the plates. The ball represents a plume, and the sheet, a tectonic plate. TOOMEY: This ball, made of Styrofoam, that, clearly very buoyant, and wants to rise quickly through the water, and it'll mimic the buoyancy we have in the earth.
15:57
NARRATOR: The data confirms buoyancy has helped lock the Cascadia fault for more than three centuries. As the North American plate bends like a spring, more energy builds up. The longer it builds, the greater the power unleashed when one plate finally slips. TOOMEY: It's accumulating all that deformation. But eventually all that has to be released.
16:24
So, at some point in the future it's going to slip catastrophically.
16:32
NARRATOR: Millions live in the shadow of this natural disaster. TOOMEY: The question is, you know, when's the next one? (rumbling) (siren)
16:49
NARRATOR: Most natural hazards give warning before they strike. Hurricanes. Even volcanic eruptions. But predicting when the earth will quake is like predicting when a temperamental child will erupt. Good luck.
17:11
TOBIN: Every day is earthquake season. And you'll hear people talk about earthquake weather. And people have studied this intensively, there just is no such thing. There's no particular time of year they strike. There's no particular phase of the moon when they strike. None of those things really make a difference for these very large earthquakes.
17:38
GOLDFINGER: We know energy is going into the system. The one thing that we all wish we could tell is how much energy has it stored. It's like a charging battery. You put the leads on and turned it on, and then the little red light is blinking, but we don't have the dial that says how full the charge is. (beeping)
18:05
NARRATOR: Professor Goldfinger can't foretell the next quake to strike his home, the Pacific Northwest. But he can search for clues in the past. GOLDFINGER: The thing about earthquakes is, if it happened once, it's probably happened a thousand times.
18:24
NARRATOR: Professor Goldfinger looks for a pattern to the Cascadia fault quakes, but not on land.
18:33
For years, scientists have been extracting cores of sediment from the sea floor.
18:42
GOLDFINGER: It's a very quiet environment. Sediment just rains down. It's a very smooth-running tape recorder. NARRATOR: This section comes from the megathrust earthquake of 1700. The disturbed sediment was washed off the land during the great quake. GOLDFINGER: There's 300 to 400 years of material here. And this is the sea floor as it was just a few minutes before the earthquake. NARRATOR: It's a dirty record of half a dozen quakes across thousands of years.
19:16
GOLDFINGER: You can just visually see, here's an earthquake, earthquake, earthquake, earthquake, another earthquake, another earthquake. I kind of look at these sort of like barcodes. NARRATOR: Magnitude 8 earthquakes, still huge, occur on average every 240 years. The very largest and most destructive, magnitude 9, show up on average every 500 years. In the last 10,000 years, the Cascadia fault has produced a megathrust earthquake 19 times. The last time was in 1700, 320 years ago.
19:56
But the time between huge quakes is erratic; anything from 200 to 1,000 years. (horn honks) A major earthquake could hit Portland and Seattle at any time. GOLDFINGER: All the lines of evidence are all converging at the same answer. It's one of the most airtight cases that I've ever seen. NARRATOR: Professor Goldfinger knows how bad it could be. GOLDFINGER: Even for Californians, like me, an earthquake is typically 15 to 20 seconds. These last, can go as long as 5 minutes.
20:34
Which is just an eternity if you're in one. NARRATOR: And in 2011 Professor Goldfinger was. He was in Japan for an earthquake conference when the mag 9 hit Tohoku. GOLDFINGER: Japan can take a hit like that. And the recent disaster there you'd have to call a success.
20:55
Except for the coastal defenses, which were overwhelmed by too big of a tsunami, Japan had very little structural damage. (scream)
21:07
OPERATOR: 911. What happened? MAN: There's a hell of an earthquake.
21:13
NARRATOR: Structural engineer Reginald DesRoches has also felt devastating quakes firsthand. In October 1989, a magnitude 6.9 quake devastated Loma Prieta in northern California. WOMAN: Can you feel that?
21:29
REGINALD DESROCHES: I was in it, I was a student at the time on Berkeley's campus. From where I was, I could see smoke coming from the Bay Bridge. NARRATOR: The quake shook the Bay Bridge and the double-decked Cypress Freeway.
21:47
MAN: This is engine one. Check, get a battalion chief down here. We've got four injured out here. DESROCHES: One span collapsed onto the other span for a section of around a mile, and trapping people in between the two large sections of the concrete bridge, where the majority of the fatalities occurred. NARRATOR: 15 seconds.
22:08
63 dead.
22:12
$6 billion of damage. Like most of the Pacific Northwest, San Francisco Bay is built largely on solid bedrock, through which seismic waves travel fast. But geologists have found large anomalies beneath the populous coast that are something else.
22:37
The largest is more than 40 miles across. ♪ ♪ Five miles beneath the surface, the x-ray reveals a huge bowl of hard rock, filled to the brim with layers of soft, weak sediments. A sedimentary basin.
23:02
For the last 5 years, geophysicist Erin Wirth has studied how an earthquake would interact with this huge geological feature. WIRTH: Because that material is so weak, when seismic waves enter it, the sedimentary material shakes much more than the regions surrounding it. NARRATOR: Just like this. WIRTH: When seismic waves hit the edge of this basin, waves will get trapped, bounce around, and that contributes to the longer duration and stronger shaking.
23:34
NARRATOR: And that's a colossal problem. Because nearly 200 years ago, settlers built something atop one particular basin: Seattle. How bad could a megaquake be for its 750,000 residents?
23:53
To find out, Professor Wirth conducts a supercomputer simulation.
24:00
WIRTH: Seismic waves are hitting Portland, La Grande and Crescent City. Although Seattle and La Grande are the same distance away from the megathrust fault, you can really see that Seattle is shaking longer and stronger than La Grande. ♪ ♪ ♪ ♪ NARRATOR: The Loma Prieta earthquake lasted just 15 seconds. If a magnitude 9 quake hits, it will be 125 times bigger. Seattle could shake for more than 5 minutes. WIRTH: I do think about this place is capable of having earthquakes.
24:43
But we live here because it's beautiful, because we love it here. But it's a bit of a trade-off, and it's a risk, because there is a lot of buildings that are not seismically safe. Some of those are schools. And that does make me nervous, having a daughter. ♪ ♪ GOLDFINGER: We're in a race, and it's a race that we're going to lose. We already know we're going to lose. It's just a question of how much?
25:18
NARRATOR: Like the rest of the Pacific Northwest, Seattle braces for disaster. ♪ ♪ X-raying the earth has helped uncover the clues to the geological time bomb. But if the worst should happen, how bad would the damage be to this historic city? A team of engineers and scientists take to the streets to investigate. Geophysicist Lee Liberty hopes to forecast the scale of the damage by creating his own mini earthquakes. LEE LIBERTY: We want to understand how this region
25:55
will be impacted by a large earthquake. So, we're measuring the ground vibrations every time the hammer hits the ground.
26:05
NARRATOR: Across town, Harvard seismologist Marine Denolle places earthquake sensors in backyards. MARINE DENOLLE: Hello. LIBERTY: She's doing passive seismology, so she's listening for traffic noise, for wave action from the ocean. Those noise sources are in a better frequency range for a Cascadia-type earthquake. NARRATOR: She enlists Seattle residents in a citizen science study. NANNETTE MARTIN: Sometimes I worry about it. What if the tree falls on the shed
26:32
or the house collapses on the basement? The more information that we have, the better.
26:41
JOYCE MOTY: I think it could be pretty devastating, and the only thing I hope is, I never am around to experience it.
26:53
DENOLLE: We're trying to provide scenarios of shaking that then we give to earthquake engineers and say, "Hey, look, in this area we expect the shaking to be that long, with that type of frequency. Now please design a code for the buildings there to be built to sustain this."
27:14
NARRATOR: Downtown in Pioneer Square, structural engineer Reginald DesRoches assesses the threat to Seattle's history. DESROCHES: They were built before we knew how to build these structures to be safe in earthquakes, and certainly before we knew of the hazard that exists here.
27:30
NARRATOR: Most are built of simple brick and mortar.
27:35
DESROCHES: When the earthquake begins to occur, shaking happens and these walls tend to fall out, they tend to crumble, they tend to shear. If this moves this way, these are very, very brittle. They'll just crack and they'll likely fall out. ♪ ♪ NARRATOR: Seattle is in a race to shore up its past. But a long duration quake also threatens its modern buildings. A $100 million re-fit has helped make the iconic Space Needle earthquake-proof. One down, dozens to go.
28:13
And remember, Seattle sits on a sedimentary basin, the geological equivalent of a castle built on sand. DESROCHES: We know that a basin will amplify the magnitude of the actual earthquake, and the ground shaking would be significantly larger. The other concern is it slows down the actual shaking. NARRATOR: Imagine a skyscraper as a giant tuning fork. DESROCHES: You're going to really feel the effects. It will move tens of feet at the very top of the structure.
28:42
We haven't really seen that level of shaking to this type of structure in the US ever. 9.0 and above is not something that these structures are really designed to handle. ♪ ♪ (screaming) NARRATOR: It's not just the sedimentary basin that could make a Cascadia fault quake so deadly.
29:08
Kobe, Japan. A magnitude 6.9 quake shook the port. Tens of thousands were killed or injured. Some of the worst destruction took place on land reclaimed from the sea. The ground turned to quicksand. It's called liquefaction.
29:36
Land is reclaimed by pouring infill over water or marshland to create solid ground. But beneath the surface it's saturated with water. When the earthquake hits, the infill is shaken apart, and the water trapped below rises, turning solid ground to quicksand. DESROCHES: It's coming out, it's liquefying, and you see the structure itself is starting to lean over. (hammering) NARRATOR: Could this happen in the Pacific Northwest? ♪ ♪ Earthquake hazard reports reveal pockets
30:21
of liquefiable land surrounding Seattle and Portland. One area, on the edge of Oregon's Willamette River, alarms engineers. It's made of two distinct layers. On top is new, densely packed soil. But the layer below is saturated with water: perfect conditions for liquefaction. If the land were vacant, the risk would be slight. But it's not.
30:55
It's a huge depot that stores 90% of Oregon's gasoline and diesel, six miles along the banks of the Willamette River. A magnitude 9 earthquake could be disastrous. DESROCHES: You'll see these tanks sort of moving. At some point within a few seconds you'll see the soil starting to fail. It loses all its resistance to be able to carry any sort of load. Almost like quicksand, it becomes a liquid, and everything sinks into it. In some cases, you'll see the whole barrier fail,
31:30
and they'll come out to the river and begin to float. NARRATOR: Millions of gallons of highly flammable fuel could flood the river.
31:41
Just downstream from the depot are high-voltage cables. DESROCHES: These towers are very, very tall, very flexible towers; they're going to be susceptible to liquefaction. NARRATOR: If the towers fall, a single spark could ignite the fuel. Portland's lifeline could become a river of fire.
32:05
(siren) Cities destroyed. (crash)
32:12
Rivers ablaze.
32:18
And that's just the start.
32:27
GARRISON-LANEY: We're at a location about two kilometers from the ocean.
32:35
NARRATOR: In the Pacific Northwest, along the Copalis River, geologist Carrie Garrison-Laney finds evidence of the last earthquake to strike Cascadia, 320 years ago. GARRISON-LANEY: This is telling us a story of pretty incredible, pretty incredible proportions. NARRATOR: The disaster didn't end when the shaking stopped. GARRISON-LANEY: We see an abrupt change from forest soil to a thick layer of sand here, and that tells us that there was a tsunami big enough
33:08
to transport sand from the beach all the way this far inland.
33:17
NARRATOR: In 2011, an earthquake of similar power to the 1700 event shook Japan.
33:25
It triggered a tsunami up to 130 feet high. GARRISON-LANEY: There's really no surviving an event like that.
33:36
It doesn't take a very tall tsunami to knock people over, move cars, knock buildings off their foundations.
33:46
NARRATOR: The evidence shows the Cascadia tsunami traveled at least a mile and half inland. And it will happen again. ♪ ♪ TOBIN: I worry a lot about the largest loss of life from a Cascadia subduction zone event being the tsunami along the shore rather than the earthquake shaking itself. That's really a frightening thought.
34:18
MAXIMILLIAN DIXON: It's so overwhelming, it's so devastating, it's so scary, that a lot of folks are apathetic. They feel that there isn't really anything that they can do to help save their own lives. (alarm) But there are ways to protect you, there are ways to survive this. If you get prepared, you can survive. NARRATOR: One town has taken matters into its own hands. WOMAN ON LOUDSPEAKER: Attention students and staff, we will now conduct an earthquake and tsunami drill.
34:47
CINDY RISHER: The students will drop and cover in their classrooms. NARRATOR: Ocosta Elementary in Westport, Washington, has North America's first tsunami evacuation towers, paid for by the town itself. RISHER: The four towers act similar to a tabletop in that they provide the four legs to hold up the roof surface. The top of the towers are about 54 feet above sea level. The walls actually will break away and wash out from underneath. Once at the top of the stairwell
35:29
the whole community of Westport would come here. And once the wave hits, everything washes out from underneath with the legs holding everything stable and us well above the water.
35:46
NARRATOR: This one building could save more than a thousand people, but only if they're warned in time to use it.
35:57
Despite decades of research, no one can predict when the next big one will strike. TOBIN: They're fiendishly difficult. They're not like hurricanes where we see them coming. They're not even like volcanic eruptions where the volcano starts rumbling and emitting gases. Earthquakes tend to build up their strain for hundreds of years and then strike without warning in a few seconds.
36:21
NARRATOR: At the Pacific Northwest Seismic Network, they're testing a warning system. TOBIN: Earthquakes send out different kinds of waves. The first waves, the P-waves, are fast, but they're not particularly damaging.
36:38
The waves that follow them, much more slowly, like ripples in a pond, are surface waves.
36:45
They move more slowly but they cause much stronger shaking of the ground. They're the damaging waves. COMPUTER: Earthquake, earthquake. (alarm sounds) DOUG GIBBONS: So this is a simulation of an earthquake directly west of Seattle. NARRATOR: The shake alert system first detects the arrival of the faster P-waves, shown in yellow.
37:08
The lethal S-waves, in red, travel at about half the speed. Buying vital seconds to warn people to duck, cover and hold on. The farther from the hypocenter, the greater the warning. COMPUTER: Shaking expected in 12 seconds. GIBBONS: Within 3 to 5 seconds after the earthquake initiates, we have calculated a magnitude and a location for that earthquake, and then sent out this earthquake early warning or shake alert message. NARRATOR: When shake alert is triggered, seconds count.
37:41
It instantly sends text warnings, and it can automatically shut down vital infrastructure. GIBBONS: Water lines, gas lines, the electrical grid: we can open elevators on large buildings. We can turn traffic lights red. Imagine if you could stop cars on the freeway or prevent them from driving onto a bridge; slowing a train down to prevent derailment. COMPUTER: Shaking expected in 3 seconds. (alarm sounds)
38:12
DESROCHES: The science is rock solid that there will be an earthquake here. There will be a large one. TOOMEY: It's no longer a question of if we're going to have an earthquake and tsunami; it's a question of when. (car alarm) (rumbling)
38:32
NARRATOR: Scientists believe a worst-case scenario could begin in southern Oregon, and might unfold like this...
38:43
A megaquake. After building up pressure for three centuries, the North American plate slips catastrophically across the Pacific floor at the southern end of the Cascadia fault.
38:59
The entire 620 miles of the fault begins to rupture. TOOMEY: You're looking at several hundred seconds of that thing unzipping. NARRATOR: Fast-moving seismic P-waves radiate out and hit the coast. TOBIN: Within a few seconds of the beginning of the earthquake, the seismic sensors that are along the coast would detect it. COMPUTER: Earthquake, earthquake. TOBIN: And they would issue a shake alert immediately. (text alerts beeping) NARRATOR: Seattle residents have just three minutes
39:31
before the big one hits.
39:36
30 seconds after the earthquake begins, the lethal S-waves reach the coast. TOOMEY: The shaking's going to be violent for minutes. GOLDFINGER: You could probably see the beach just rippling as it came down and disappeared in the other direction.
39:55
NARRATOR: Three minutes after the rupture, the S-waves strike Seattle.
40:03
DESROCHES: And the ground starts to shake, and the building begins to move. NARRATOR: The sedimentary basin under the city traps the seismic waves, amplifying their violence and duration. Anything old and unreinforced is history.
40:25
DESROCHES: These structures just can't take that kind of shaking. NARRATOR: As the shaking slows and strengthens in the basin, taller buildings tune into the earthquake. TOBIN: There is a real danger that tall buildings can develop those resonant frequencies.
40:41
DESROCHES: They'll sway tens of feet in some cases. TOBIN: You couldn't evacuate if you wanted to. You couldn't even stay on your feet. It would be an incredibly frightening time for people. (glass shattering)
40:57
NARRATOR: Across Cascadia, reclaimed land turns to quicksand. DESROCHES You will start to see structures begin to tilt, in some cases go all the way in. NARRATOR: Ruptured fuel lines spew gas into the Willamette River. ♪ ♪ ♪ ♪ DESROCHES: These things begin to cascade. The power system goes out, then you have the water failing, and you don't have water to be able to put out the fires. And then you lose access to your roads and bridges. (siren) (siren) NARRATOR: After almost 5 minutes,
41:44
Seattle finally stops shaking. (siren) Along the coast, the danger is just beginning. (alarm) When the fault ruptured, the edge of North America jumped up almost 120 feet instantly displacing a vast volume of ocean.
42:11
(alarm) People on the coast know what's coming. GOLDFINGER: Imagine going through an M9 earthquake and 3 to 5 minutes of that, then the stopwatch starts. NARRATOR: They have just minutes to escape. DIXON: If the water rapidly recedes and fish are flopping around, that is a huge warning sign that a tsunami is coming.
42:34
NARRATOR: A mile inland, up to a thousand citizens race for the safety of the reinforced roof of the Ocosta school. A wall of water up to 80 feet high smashes into the shore, scouring everything in its path. DIXON: This is the entire ocean moving towards you like trains hitting you. And you are going to have massive debris.
42:59
TOOMEY It's going to slam you, and there is going to be very little hope for anything but drowning.
43:08
NARRATOR: More than 600 miles of the Pacific Northwest coast is devastated. ♪ ♪ ♪ ♪ TOBIN: For a single event, the Cascadia subduction zone earthquake would be a giant like we've never seen before.
43:31
(siren) DIXON: It's going to take us years, if not decades to recover. (siren) NARRATOR: The toll of dead or injured could reach 45,000. Twice as many victims as Japan's quake in 2011. The repair bill could top $100 billion. TOBIN: It's going to be one of the most, if not the most devastating event that's ever taken place, you know, in North America. NUNN: Mother Nature is king.
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It humbles us.
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