MegaQuake Could Hit North America - BBC (Full Documentary)

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U.S. fears overdue 'megathrust' earthquake will trigger tsunami and decimate unprepared cities on north-west coast

Cascadia fault line has lain dormant for 300 years
Eruption could trigger tsunami, devastating seaside communities - and reach as far as Japan
The north-west coast of the U.S. could be devastated by a huge movement of undersea plates known as a 'megathrust' earthquake, scientists say.
A review of the dangers posed by the Juan de Fuca plate released in the wake of the Japanese quake has raised fears that the Pacific seaboard could be similarly ravaged.
The horrifying possibilities have been brought to light by data researched by the Active Tectonics and Seafloor Mapping Laboratory at Oregon State University.
And the results are shown in a documentary, Megaquake: The Hour That Shook Japan, which is set to go out on the Discovery Channel in the UK this weekend.

Read more: http://www.dailymail.co.uk/sciencetech/article-1379187/U-S-fears-overdue-megathrust-earthquake-trigger-tsunami-decimate-unprepared-north-west.html#ixzz21efW0rM7

https://www.facebook.com/EarthquakeReporter

♪ [ominous theme music]

(male narrator) Boxing Day, 2004.

The world was shocked

by one of the worst natural
disasters of all time.

Over 250,000 people died.

The cause of this devastation

was the most powerful kind
of earthquake on the planet,

called a mega thrust.

This event made us realize
how poorly prepared we are

to face these huge geological catastrophes.

And scientists are now
trying to work out

where else is at risk.

They have discovered

that a megathrust as large
as the Sumatra quake

could hit North America.

♪ [music playing]

Everyone knows that America
is going to be struck

by a devastating earthquake.

For years, the people of California
have been waiting for the day

when the San Andreas Fault
unleashes the big one.

But all the time

an even more powerful hazard
has lain undiscovered.

A giant megathrust earthquake
just like the one that hit Indonesia

threatens America's Pacific Northwest.

A huge area from northern California

all the way to Canada is at risk,

including major cities
like Seattle and Vancouver.

(scientist) It's a major earthquake.

(emergency worker) We were just
coordinating

an emergency response that's going out.

(narrator) The authorities have
started to prepare for this catastrophe.

Rehearsals like this one help
to train the emergency services

to deal with such an event.

[screaming]

(narrator) Children are now
being taught lessons in survival

that could mean the difference
between life and death.

The source of all this danger,

lying underwater off
the Pacific Northwest coast,

is a huge gash in the earth's crust,

a subduction zone.

The earth's crust is made up
of huge plates of rock

that are constantly in motion.

Where two of these giant
plates meet head to head,

one of them can get pushed
down under the other.

This is a subduction zone.

It was a subduction zone
off the coast of Sumatra

that caused the Boxing Day earthquake.

And worldwide there are
many other similar faults.

(Prof. Bill McGuire) There are
subduction zones all over the planet,

but mainly they occur
around the rim of the Pacific,

the so-called "Ring of Fire" and
lots of big earthquake occur there,

most of the world's really
destructive earthquakes.

(narrator) Subduction zones
cause earthquakes

when the plate that's being
pushed down gets stuck.

As it pushes, the upper plate
gets squeezed and distorted.

Eventually the strain becomes too much.

The upper plate slips creating
a megathrust earthquake.

(Tim Walsh) A megathrust earthquake
happens when the subducting slab,

which is diving under
the overriding plate,

is locked and causes the overriding
plate to bulge upward.

And then when that becomes unlocked,

it slides suddenly creating
a huge earthquake.

Worldwide, these are
the biggest earthquakes.

They range in magnitude
up to nine and a half.

(Prof. Bill McGuire) Generally speaking,
if you have two great masses of rock

and you're scraping them,

one underneath the other,

they're not going to move very easily

and you're going to get
a lot of friction there.

And I liken it to sort of two cheese
graters pushing past one another,

very, very difficult to get any
smooth sort of movement there.

(narrator) But as the 26th
of December showed,

megathrust earthquakes have
another devastating consequence.

(Prof. McGuire) In the case
of a megathrust earthquake,

the overlying plate,

which has been bent,

pins back upwards into position.

And it's that sort of pinning motion

that transmits an enormous amount
of energy to the sea bed.

That energy is then transmitted
to the water above it

which oscillates up and down

and then moves out
as a series of huge ripples.

And that, in a sense,
is what a tsunami is.

(narrator) A tsunami is very
different from a normal wave.

In normal waves, only the water
on the surface is moving.

But a tsunami involves the movement
of the whole water column,

millions of tons of water.

(Prof. McGuire) Normal wind driven
waves have very small wavelengths,

that's from crest to crest.

So it maybe a few tens of meters

and the wave has crashed
and it's gone.

Tsunami have a wavelength that
could be hundreds of kilometers long.

So when that initial wave comes in,

the water behind it is pretty much
at the same level.

And that can keep coming for five
or ten minutes as a huge flood.

And that's why they're so destructive.

It's not a simple wave that you can
hold your breath under and survive.

(narrator) The combination of
massive earthquakes and tsunamis

makes subduction zones
a deadly geological hazard.

And so it should have been
a cause for concern

that the Cascadia subduction zone,

a 600 mile long fault,

lies right off the Pacific Northwest coast.

The strange thing was
Cascadia didn't seem to be a danger at all.

For years, scientists have been
monitoring seismic activity

along the Cascadia subduction zone.

They found that unlike
other subduction zones,

it was virtually silent.

(Robert) People saw that Cascadia had
many of the features of a subduction zone.

It had an oceanic trench.

It had a line of volcanoes
above the subduction zone.

It simply didn't seem to
have big earthquakes

and so they put it in a category of its own,

the subduction zone that
doesn't have big earthquakes.

(narrator) And there was
a simple explanation

for why Cascadia wasn't creating earthquakes.

If the plates were moving
smoothly past each other,

there would be no strain being built up
and no earthquakes.

♪ [music playing]

This theory was backed up by
over 200 years of historical record.

For as long as the Europeans
have lived here,

there's no record of any significant
earthquakes from Cascadia.

But in this region,

there is another kind of history,

a kind that isn't written down.

For centuries before the Europeans arrived,

this land was home to native peoples.

Viola Riebe is a member of the Ho nation
on the northern Washington coast.

As a child she was taught the legend
of the Thunderbird.

(Viola Riebe) The Thunderbird
lives in the glacier

at the headwaters of the Ho River.

When he comes out,

the ground would start to shake

and he would even make
the waters troubled.

(narrator) Could this legend
be describing a real event,

a megathrust earthquake
that occurred long ago?

Most geologists have no time
for such speculation.

But one decided to take a closer look.

♪ [guitar music]

(narrator) Brian Atwater wondered whether
the native legends might be a warning

that the Pacific Northwest could
be at risk from giant earthquakes.

So he took to his canoe

and started exploring the marshes
and rivers of the Washington coast.

He was hoping that
the layers of mud here,

laid down over centuries

might provide a clue
to the events of the past.

And buried in the marsh,

he did find evidence
of an unusual event.

(Brian Atwater) We're on
an ordinary coast,

standing on a salt marsh like this one.

Underneath we find salt marsh deposits,

salt marsh deposits,

salt marsh deposits,

just steadily on.

But here we have something
completely different.

We've got a spruce forest here,

underneath the salt marsh.

We can dig out here

the bark,

the bark of Cyprus spruce.

(narrator) These trees can
only grow on dry land.

Yet this layer of trees
was covered with mud

that must have been deposited by water.

So the land here must once have been
higher and then at some point,

it dropped down,

plunging the forest underwater.

(Brian Atwater) At the time that
the spruce forest dropped down,

sand was laid down.

It's the first thing that covers
the peat is a little skin of sand.

So that's the mystery.
How did that happen?

(narrator) Since there's no sand nearby,

there must have been
a sudden rush of seawater

that carried the sand in with it.

This was no gradual change in land level.

It must have been a violent collapse.

(Brian Atwater) The easiest
explanation for that

is that you had an earthquake

that caused the land here to drop

and also warped the sea floor.

That warping of the sea floor set off a tsunami,

and the tsunami then lays down the sand

on the freshly down-dropped land surface.

(narrator) Carbon dating
of the buried trees

showed that this event had occurred
roughly 300 years ago,

before Europeans had arrived.

So the native legends might
indeed be about a real event.

But it would need more than
just layers of mud

to prove that there had been
a devastating earthquake here.

The next piece of evidence was to
come from thousands of miles away.

As the Indonesia earthquake has shown,

megathrust earthquakes cause
damage at astonishing distances

because they create tsunamis.

If such an earthquake really
had occurred in Cascadia,

it should have created a tsunami capable
of traveling right across the Pacific

to countries like Japan.

Kenji Satake is a geologist who
studies earthquakes and tsunamis.

When Satake heard about
Brian Atwater's theory,

he realized Japan could hold the answer.

(Kenji Satake) 300 years ago
is prehistoric time for Americans,

but in Japan, we have documents

that would record the tsunami
from Cascadia 300 years ago.

So that's why we started
looking for the records.

(narrator) What Satake was looking for

was a very special kind of tsunami.

Most tsunamis in Japan are
caused by nearby earthquakes,

so they're accompanied
by shaking of the ground.

But a few tsunamis arrive
without shaking

because the parent earthquake is far away.

When there's no known earthquake
that could have caused the wave,

it's called an orphan tsunami.

So Satake started hunting for
records of an orphan tsunami

that could have come
from the Pacific Northwest.

And in the coastal town of Miho,
southwest of Tokyo,

there's a document that
describes just such a tsunami.

(Kenji Satake) This page describes
a tsunami on January 28th of 1700.

On that day, from morning,
tsunami arrived at this town,

like a high tide,

and the receding wave was like big river

and it continued seven times
until the noon of that day.

(narrator) The account told how
the villagers took refuge in a shrine

that still exists today.

The author also recorded

that this tsunami was unlike any
that he had experienced before.

(Kenji Satake) Writer note that
there was no earthquake

but the tsunami arrived.

So he was surprised.

And he said such a strange thing

should be passed
to the future generation.

(narrator) Crucially, the same tsunami
was recorded in four other accounts

from different parts of Japan.

So this couldn't be a local event.

Satake thought this tsunami

might indeed have come from
a huge megathrust earthquake

5000 miles away in Cascadia.

But still there was no proof

that the tsunami had come
from North America.

The carbon dating only showed that

the Cascadia event had happened
at roughly the same time

as the orphan tsunami.

The final piece of evidence would
be found in a mysterious corner

of the Pacific Northwest.

A hundred miles southwest of Seattle,

in a remote area of the Washington coast,

is the ghost forest.

These are trees that died
hundreds of years ago

that remain standing to this day.

(David Yumaguchi) Sometime in the past,

this would have been an
in intact red cedar forest,

large trees standing 100 feet
or more in the air

and this landscape was filled with them

and then one day, something
killed the trees here in place.

And the mystery is,
"What killed them?"

you know, what could kill an entire forest

along 60 miles of Washington coast
just like this?

[chainsaw starts up]

(narrator) Tree specialist David
Yumaguchi has spent years

trying to solve the mystery of
what happened to the trees.

He wanted to work out
when they had died

by looking at their tree rings.

(David Yumaguchi) Most people
know that trees have annual rings.

So depending on the climate
from year to year,

the tree rings are either wide
or narrow or wide or narrow.

And so the developing of bar code
going back in time,

it's unique in time.

(narrator) Using this pattern,

David was able to work out exactly
when the trees had died.

And he found out that all of them

had died around the early months of 1700.

(David Yumaguchi) The summer
before the tsunami hit Japan,

these trees were just growing
happily in the forest here.

Then the winter came along

and by the following summer,

they were all dead.

And so the tree ring story matched
the Japanese tsunami records perfectly.

(narrator) There was now no doubt

that the same catastrophe
that had killed the ghost forest

had also sent the tsunami across to Japan.

And from the Japanese records,

Kenji Satake could work out exactly
when it had happened,

on the 26th of January, 1700, at 9 p.m.

On that winter's night,

a megathrust earthquake just like
the Boxing Day earthquake of 2004,

struck the Pacific Northwest.

It drowned forests
and turned land into sea.

It sent a tsunami hurtling
across the Pacific.

And it spawned a legend

that would be passed down
to a dozen generations.

The scientists knew that
if it had happened here once,

it would happen again.

One day the people of the Pacific
Northwest will face a megathrust earthquake.

So how big will it be?

What damage will it cause?

And when will it happen?

The first question is,
"How large will the earthquake be?"

The power of an earthquake depends
on the size of the fault that breaks.

In the case of the Boxing Day earthquake,

it was huge,

over 600 miles of fault ruptured.

The Cascadia subduction zone
is almost exactly the same length.

So it's likely that it will create
an equally powerful earthquake.

(Robert Muir-Wood) Now
we do not know exactly

where the next Cascadia
earthquake is going to occur,

but we do know that

the impact of that earthquake
in terms of the ground shaking,

the huge area impacted,

the extent of land level changes,

the size of the tsunami
which will be generated,

will be very comparable

to that which was seen
on December the 26th in 2004.

(narrator) Scientists believe
the next Cascadia earthquake

will be one of the largest on the planet,

up to magnitude 9.

The Kobe earthquake
which killed 6000 people

and devastated the Japanese
economy was a magnitude 6.8.

The terrible Mexico City earthquake

which killed over 10,000 people was 8.1.

But a magnitude 9 releases many
times more energy than those.

(Tim Walsh) The magnitude
scale is logarithmic,

that is each one is 10 times bigger
than the previous number.

But that's the amount of displacement.

When you do that
in terms of energy release,

each one is 30 to 40 times
bigger than the previous one.

So a magnitude 9 has 1000 times
more energy released

than does a magnitude 7,

30,000 more than a magnitude 6.

So to put that in perspective,

the Kobe earthquake that
was so damaging in Japan,

was about a magnitude 6.8.

So a Cascadia event that
would reach magnitude 9

is more than 1000 times
bigger than that one.

(narrator) Just as happened
in the Indian Ocean,

this huge earthquake will cause
a sudden uplift of the sea floor.

And that will create a tsunami.

The Boxing Day tsunami

devastated the densely populated
northwest coast of Sumatra,

and almost totally destroyed
the town of Banda Aceh.

The cities of Seattle, Portland,
and Vancouver

will at least be spared that fate.

(Robert Muir-Wood) One of the
fortunate things about Cascadia

in comparison with northern Sumatra
is that the big towns and cities

aren't located right out
on the open ocean coast.

The complex of waterways in Washington
State means that the big ports

are actually located someway inland.

(narrator) However,
thousands of people do live

on the Pacific Northwest coast.

And in summer, the beaches
are a major draw to tourists.

(Tim Walsh) A lot of the population
on the Washington coast is vacationers.

The population can grow from just a
few thousand permanent population

to tens of thousands of visitors.

And if we have a Cascadia
subduction zone earthquake and tsunami

the wave crest would arrive
at Ocean Shores and Long Beach

within about a half hour

and that's a very short period of time

to be able to move a lot of people off
those peninsulas to high ground.

(narrator) So even though there are
no major cities on the coast,

there will still be many thousands
of people at risk from the tsunami.

But far more people will be
affected by the earthquake itself.

All the major cities in Washington,
Oregon, and British Colombia

are going to experience
strong ground shaking.

And this megathrust earthquake will
be very different from a normal quake.

(Robert Muir-Wood) Magnitude 9
earthquakes have these special characteristics.

One of them is that it takes
several minutes

for the fault to break
from one end to the other.

The fault rupture spreads out
a few kilometers a second,

but it still may take two or three minutes
to get from one end to the other.

And that means the earthquake
shaking goes on

for a very long period of time.

(narrator) If the full 600 mile length
of the Cascadia subduction zone ruptures,

it will mean the earthquake will
continue for as long as five minutes,

just like the Indonesian earthquake did.

(Prof. McGuire) The duration
of the event is very unusual

and in that sense alone
it can cause more damage.

An earthquake that goes on for longer

causes more damage generally than one
that is over within 10 or 20 seconds.

(narrator) So what damage will
several minutes of shaking do

to cities like Seattle?

Even though the Boxing Day earthquake
and the next Cascadia earthquake

may be very similar,

they could have very different effects.

In Indonesia, most of the damage
was caused by the tsunami

not the earthquake itself.

(Robert Muir-Wood) Most people's
houses are built out of wood.

There's some more modern
concrete construction,

but typically only one or two story buildings,

so these buildings are not sensitive

to the very long period ground motions

we can expect from
a magnitude 9 earthquake.

(narrator) But the modern high-rise
structures of the Pacific Northwest

may react very differently.

♪ [piano music]

Tom Heaton is an earthquake
engineer from California.

He was brought in to advise on the
construction of a nuclear power station

near the Washington coast.

In the end, the project ran out of
money and was never completed.

But ever since,
Heaton has been concerned

by the question of what damage
a Cascadia earthquake could do,

particularly to skyscrapers.

(Tom Heaton) My fear is that in
a Cascadia event these buildings

may sway some large distance

as we get a very long
duration of shaking

that the swaying may grow in intensity

and the buildings may begin to be damaged.

(narrator) But not everyone agrees.

John Hooper is a buildings engineer

who has worked on many
of Seattle's tallest buildings.

He believes that the modern
skyscrapers, at least,

should be strong enough
to avoid serious damage.

(John Hooper) The majority
of the high-rises here,

they'll move.

And they'll move a lot.

But they're designed to withstand
that motion and that energy absorption

and they go through that
8 or 10 foot drift, back and forth

during the earthquake for several minutes,

scaring a lot of people probably,

but the damage should be related
mainly to the nonstructural components

and not to the major structural
elements themselves.

(narrator) The reality is,

no one knows for sure.

Because there has never been
a megathrust earthquake

near a modern high-rise city.

(Tom Heaton) These very large
earthquakes don't happen often

and for us to understand what it is
we need to do in the first place

so the building codes have
never really been tested

by an earthquake of this nature,

at least not for tall buildings.

The lessons haven't been learned yet.

So what concerns me is that

we may learn the lesson
in a very difficult way.

(narrator) But there is a type of building
that everyone agrees will be at risk.

The older brick buildings known as
unreinforced masonry, or URMs.

(John Hooper) These buildings we see
around here in [inaudible]Square

are like many cities on the west coast.

They are constructed of
unreinforced masonry,

brick stacked upon brick,
separated by mortar

and so if an earthquake shaking happens,

those brick end up sliding
past one another,

they lift apart.

(narrator) URM buildings are
very weak and very brittle.

So the long duration of shaking that
a megathrust earthquake will produce

could cause many to collapse.

(John Hooper) URM buildings have
been noticeably not very resistant

to earthquakes in general.

And if you don't do some renovations

and start connecting the pieces together,

they're very susceptible to damage,

especially during a long event
like the Cascadia.

And so even those that do have some
improvements made to them,

they still might be challenged.

But those that don't' have any,

their chances of surviving
is probably fairly limited.

(narrator) There are thousands of
these unreinforced masonry buildings

in the earthquake zone.

They are used as homes,
offices, and schools.

The collapse of such buildings is likely
to be a major cause of death and injury

when the next Cascadia earthquake occurs.

So the big question is,

"When will it happen?"

Predicting earthquakes is impossible.

No one could have known that

the Indonesian earthquake
was about to happen

and no one can say
when Cascadia will strike.

But it is possible to look back
at the geological record

and see how frequently earthquakes
occur on a particular fault.

Sure enough,

the Washington coast does hold traces

of several past megathrust earthquakes

from even before 1700.

(Brian Atwater) About 2,500 years
of earthquake history,

one, two, three, four events recorded.

Radio carbon ages show that

this event happened
about 600 years BC

and that this event happened
about AD 400.

So something about 1000 years
between this event and this event,

a very, very long time.

This event's from about AD 700.

There are only about three centuries
between this event and this event.

This is about the same amount of time
as between here and today.

So this is why it would not be
surprising if,

while we're standing here,

another one of these great
Cascadia earthquakes happened

and we have to run to high ground.

(narrator) And that is the problem.

The next megathrust earthquake
may not happen for centuries.

Or it could be imminent.

No one knows.

We don't know whether the entire
Cascadia fault will rupture

like it did in 1700.

We don't know how badly affected
the modern cities will be.

But Yumei Wang, director
of Geo Hazards for Oregon,

believes we must still take action.

(Yumei Wang) We know that a
Cascadia earthquake is inevitable.

We can't prevent earthquakes.

But one thing that we can do
is prevent a lot of the damage.

We can save lives if we prepare now.

(narrator) That preparation must be
based on our current understanding

of what the next Cascadia
earthquake will be like.

What follows is a reconstruction

based on the knowledge of leading
experts of what may happen;

what it would look and feel like to
experience a megathrust earthquake.

(Tim Walsh) We don't know what
actually sets the earthquake off.

But typically it would probably start
at some rough spot on the fault.

(narrator) The rupture is most
likely to start at one end of the fault.

It would then spread along the fault
at over 7000 miles per hour.

As it tears, the North American plate
which has been pushed inward

would spring back, releasing the strain.

(Robert Muir-Wood) There may be
a region 4 or 500 kilometers long

where the seafloor has suddenly
risen up by 2 or 3 meters.

It happens so fast that it lifts up
the whole body of the water on top of it.

And as a result, suddenly the sea
surface finds itself 2 or 3 meters higher

than it was before,

over a large area,
and that sets off a wave.

(narrator) This is the tsunami

which would radiate out in all directions.

Part of it would head out into the Pacific.

And part would head directly
for the coast of North America.

(Tim Walsh) It travels at the same
speed roughly as an airliner

out in the open ocean,
perhaps 600 miles an hour.

(narrator) Even at that speed,

it would take many hours to
reach the other Pacific nations.

It would take 5 hours to reach Hawaii.

And more than 10 hours to reach Japan.

Thanks to the sophisticated Pacific
tsunami network,

those countries would get a warning.

(Prof. McGuire) The quake will be
detected by a network of seismographs.

The tsunami, if they form,

will be spotted and identified
and tracked by seabed sensors

which will send,
via buoys on the surface,

a radio message, via satellite,

to the emergency authorities in
the countries around the Pacific Rim

who might be affected.

It's then their job to tell their populations
to evacuate the coastal region.

(narrator) This warning system
should make the distant effect

of a Cascadia earthquake

very different from
the events of Boxing Day.

(Prof. McGuire) I think that
the loss of life remote

from the actual location of the Cascadia
earthquake will be small

when the next big event occurs.

And this is because,

although the waves travel
at the speed of a jumbo jet,

maybe 8 or 900 km an hour
across the Pacific,

it's s huge ocean basin

and it will take many hours for the wave
to reach places like Hawaii, Japan,

which will probably be badly hit,

but they will have plenty of time
to evacuate people to safe ground.

(narrator) But the situation in the
Pacific Northwest would be very different.

The tsunami would arrive there
in half an hour.

And they'd have the earthquake
to deal with first.

The seismic waves
which carry the shaking

would be travelling through the earth
at over 10,000 miles per hour,

much faster than the tsunami.

In just a few seconds
the earthquake would reach the land.

The earthquake would be at its
most violent here on the coast.

(John Hooper) There right
at ground zero, the shaking.

So the shaking they feel will be
the largest of anybody

because they're nearest
to the fault rupture.

(narrator) But the shaking wouldn't
have reached the inland cities yet.

People here wouldn't even know
that an earthquake had started.

However news would have reached
the emergency services.

This is the Washington State
Emergency Operations Center.

It would be one of the first places
to receive an alert

from the tsunami warning center.

(male # 1) Magnitude 9.

(male # 2) We're activating our EOC
to a phase 3 for a tsunami.

(narrator) Horizon filmed them
rehearsing for a major earthquake.

The two on duty officers would
immediately activate the center

and start calling in staff.

(male #2) And what could be
your possible ETA to the EOC?

(narrator) Their job would be to
coordinate the emergency response.

But there would be no time
to issue a public warning

before the earthquake hits the big cities.

Up to two minutes after
the start of the earthquake

the seismic waves would
reach the city of Seattle.

Because of the distance,

the different types of seismic wave
would have separated out

with the faster compression waves
reaching the city first.

(John Hooper) The first thing you
sense is a vertical acceleration.

You get pushed up a little bit

and you think it's maybe
it's the jolt of a train going by

or something of that type.

(Tom Heaton) But then later,

maybe 20 seconds even later
you might feel,

start to feel the shear waves coming in
which are shearing motions in the earth,

the kind of motion that
does most of the damage.

(narrator) These shear waves would
move the earth from side to side

by as much as a meter.

There would also be surface waves,

like ocean waves, rippling
through the solid earth.

(Yumei Wang) If you are in a parking lot,

it's likely that you see waves
rolling across the parking lot

like if you took a carpet and shook it.

(narrator) As the shaking
becomes more and more intense,

people would realize that
this was no ordinary earthquake.

(John Hooper) That shaking
will continue to build.

You'll feel the first sway

and it'll start to build and build and build

and you'll wonder
when it's going to stop.

(narrator) Indoors, objects and
furniture will be hurled about the room.

Parts of the building may start to fall.

(Yumei Wang) Right when you feel
the earthquake shaking,

what we train people to do
is to duck, cover, and hold.

[children screaming]

(narrator) Schools and offices now
practice this life saving maneuver.

Going under a strong desk
and holding onto it.

(Yumei Wang) Anything that might
fall won't fall on you directly.

It will fall on the table

and the whole time you protect
your [missing audio].

(narrator) For people outside,

the major hazard will be falling
debris and shattering glass.

(Yumei Wang) If you're outside somewhere,

the best thing to do is to move
quickly into open space

such as away from a building
where you might have falling objects.

(narrator) Buildings would now
be exposed to huge forces

as they're shunted back and forth.

They unreinforced masonry buildings

would be the first to suffer damage.

(Yumei Wang) The weakest points
start to fail, in most cases,

because they're older structures.

It's the mortar.

(John Hooper) The elements
that support the building vertically,

if they start to come down,

the floors themselves
potentially can come down.

(narrator) Collapsing URMs
could cause many fatalities

throughout the region.

The shaking in Seattle would now
have been going on for two minutes.

But we'd only be hallway through.

(Yumei Wang) For a typical earthquake,

if a building gets damaged
in the first 20, 30 seconds,

it very likely can remain standing.

But if that damaged building is
shaken for another three minutes

then that damage can
propagate into collapse.

(narrator) Meanwhile, the large
movements of the ground

would be making skyscrapers
bend further and further.

(Tom Heaton) you may see the buildings
begin to sway more and more violently

to the point where they start
to perhaps lose windows.

They may, in addition, start to
have some fracturing of welds

in steel frame buildings.

What happens after that
is anybody's guess.

(narrator) The worst case scenario
would be the total collapse

of a high-rise building.

Meanwhile, buildings on higher ground

would be suffering their own problems.

(Tim Walsh) Earthquakes this large
can generate landslides at distances

of up to hundreds of miles away.

(John Hooper) The classic worst
case scenario where you're on a hill,

the land slides,
your house goes with it

and the house will obviously be destroyed.

(narrator) Five minutes after
the start of the earthquake

the rupture would have reached
the northern end of the fault.

Vancouver would still be
experiencing powerful shaking,

but in Seattle, the earthquake
would finally be subsiding.

For people in buildings that
have suffered structural damage,

now it would be time to evacuate.

What would have felt like the longest
few minutes of people's lives

will finally be over.

But on the coast,

the ordeal would have only just begun.

The tsunami unleashed
by the earthquake,

would be minutes away.

For the Pacific Northwest

the tsunami warning system
that should save lives across the world,

would be virtually useless.

(Tim Walsh) There won't be time
for the tsunami warning center

to detect that earthquake,

make a determination
whether or not it was tsunamigenic ,

then send a warning down to
emergency managers in Washington

who will then send it to the people.

That would waste valuable time.

People need to know that
when they feel strong shaking

if they're on the coast,

they need to go to high ground and/or inland.

♪ [music playing]

(narrator) The tsunami will
have started out as a wave

of only a meter or two high

travelling at huge speed.

But as it nears the coast,

it starts to rise up.

(Tim Walsh) Those waves can grow.

They can amplify as more and more
water piles up in shallow water

and all of that energy
then causes the wave to

slow down and grow in amplitude

and create waves that have been
known to be hundreds of feet high.

(Robert Muir-Wood) That first wave
is often simply a step in the water level

and the water level then
stays up high for 5 or 10 minutes

before it eventually drains away again.

(narrator) Just as happened in Indonesia,

within half an hour of the earthquake,

the tsunami would rush onto the land,

more like an ever growing tide
than a normal wave.

Anyone who doesn't manage to get
inland and to high ground in time

would be unlikely to survive.

The tsunami will devastate
hundreds of miles of coast.

In total, more than 50,000 square
miles will be affected by the earthquake.

(Yumei Wang) Unfortunately,
I don't think people understand

that a Cascadia earthquake
is going to be so very different

than the other types of earthquakes
that we've all experienced,

or many of us have experienced.

One of the main differences is that
it's going to affect such a large region.

(John Hooper) It's not just going
to be city of Seattle or city of Portland.

It could be an 800 mile stretch of
Washington, Oregon, and California

that gets affected.

(narrator) Until recently,

many people would
have found it difficult

to imagine that scale of devastation.

But the Boxing Day disaster
changed all that.

(Prof. McGuire) The Indian Ocean
earthquake and tsunami

will remind these people that are
living in the Pacific Northwest that

this is something they
will have to face in the future

and the window of opportunity
that now exists

should be used to make sure that

the people that live in that
part of the word are educated

in terms of how to respond
when the earthquake happens.

(teacher) Quickly.
Quickly, all of you.

(narrator) The simple knowledge
that after an earthquake

people should move away from the ocean

and to high ground

can save lives.

The scientists who
discovered this threat

are now playing their part
in spreading the word

to as many people as possible.

(Brian Atwater) That line goes
all the way up to a salt marsh.

(narrator) Before the next earthquake.

(Yumei Wang) We knew that this
Cascadia earthquake is imminent .

It's imminent in geologic time.

So basically we're in a race against time

and the more we can get done now,

the more lives we'll save.

(David Yumaguchi) If we have
10 years, is that enough?

Probably not.

If we have 50 years, maybe, you know.

If we have a century,

you know, maybe we'll really be ready.

But do we have a century?

We don't know.

♪ [music playing]

(narrator) The Indonesian earthquake

has given the people of the Pacific Northwest

a glimpse of what
they will one day face.

Now they must heed it's warning.

♪ [theme music plays]