Original subtitles

MAN (speaking Japanese):

NARRATOR: Off the coast of northern Japan,

a Coast Guard ship comes face to face

with a 30-foot wall of water.

NARRATOR: It is the first sign of a deadly tsunami

that will soon engulf Japan's northern coastline.

More than 20,000 people will die.

Entire towns vanish.

(siren wailing)

As the giant waves reach shore and sweep inland,

NHK, Japan's national broadcaster, is on the scene,

capturing events as they unfold.

From pictures of unimaginable destruction...

To miraculous survival.

Now the people in these images are telling their own story.

At the far reaches of the tsunami, a policeman.

A family stranded on the roof of a building.

A man swept away in his car lands on top of a bridge.

Scientists in Japan are intently studying this tsunami

to help people better protect themselves in the future.

They, too, want to understand

how these victims managed to survive

when so many others didn't.

What are the lessons we can learn

about surviving a tsunami?

Right now on NOVA.

Major funding for NOVA is provided by the following:

Supporting NOVA and promoting public understanding of science.

And the Corporation for Public Broadcasting,

and by PBS viewers like you.

(rumbling)

NARRATOR: March 11, 2:46 p.m.

The eastern half of Japan was hit by a fierce tremor.

(shouting)

(man over loudspeaker)

NARRATOR: The port city of Kamaishi in northern Tohoku,

just after the earthquake hit.

The city's emergency broadcast system

announced the tsunami warning.

An NHK reporter began filming on the streets of Kamaishi.

Residents began to head

for the designated evacuation site,

a hillside overlooking the city.

(siren wailing)

Evacuees gathered on the high ground.

Fifteen minutes after the earthquake hit,

this video was taken from the hillside.

Many people still remained in the city at this time.

One of the those remaining was Saeko Kudo.

At the time of the earthquake,

she was at home with her mother, Toyoko.

The Kudos' home is in the harbor district of Kamaishi.

The harbor can be seen just 80 meters away from the house.

The high ground where many people took refuge

is a ten-minute walk.

Even closer was an eight-story building

that was a designated evacuation site.

This is the Kudos' home, facing the harbor.

At the time of the earthquake, the mother, Toyoko,

had just returned from a dialysis treatment

at the hospital.

INTERVIEWER:

TOYOKO:

NARRATOR: Saeko thought they should evacuate immediately,

but she also felt it would be hard

for her elderly mother to do so.

This was because a series of strong aftershocks

was shaking the city.

NARRATOR: The Kudos did not seek shelter immediately.

They would soon experience a terrifying ordeal.

About a half-hour after the earthquake,

the camera on the hillside captured the first signs

of the tsunami.

At that moment, Saeko Kudo also noticed the unusual condition

of the nearby harbor.

(siren wailing)

NARRATOR: At this time, the water level was rising steadily,

and water had begun to overflow the seawalls in the harbor.

But there were still many people in the city

who were unaware of this.

Machiko Kikuchi felt the tremor of the earthquake while at work.

She quickly drove home to check if her house had been damaged.

The house was 130 meters from the harbor,

but she could not see the changes taking place there.

Also, because she was in her car, she did not hear

the emergency announcement of the tsunami warning.

NARRATOR: When Machiko got out of her car in front of her house,

a passerby shouted a warning.

NARRATOR: Now aware of the danger,

Machiko hurriedly climbed back in her car.

Saeko Kudo had belatedly decided to take her mother to a shelter.

When they came out on the street,

they saw water flooding in from the harbor.

Around this time,

another taller wave was filmed as it approached the harbor.

It was flowing over the breakwater

that was built to protect the town.

NARRATOR: The tsunami was now surging into town with increased force.

The video recorded images of the Kudos' house being flooded.

The tsunami passed by the Kudos' house

and spread further into town.

The fierce wave moved quickly,

leaving people in the town no time to escape.

(rumbling)

NARRATOR: Machiko's car was thrust against a neighboring building,

where it stopped and began to sink.

After seeing the tsunami approach their second floor,

the Kudos had hurried up to the roof.

It's an open space that is partially covered by roof tiles.

The roof is seven meters high,

but the water would soon flood it with intense force.

NARRATOR: This is video footage of the Kudos' house at that moment.

Saeko and her mother are under the water

and cannot be seen.

(crashing and rumbling)

A human form becomes visible

on the tile roof of the Kudos' house.

NARRATOR: Boosted by the water onto the roof,

Saeko's figure can be seen.

This was the moment she scrambled up onto the tile roof.

Her mother was still underwater.

NARRATOR: Mother and daughter were now up on the tile roof.

They had escaped being swept away by the tsunami

and survived with their lives.

Around this time,

a woman could be seen on the roof of a building.

It was Machiko, who had been swept away in her car.

She had escaped from her car through a broken window.

She scrambled up the pile of debris around her car,

grabbed onto the window of a building

and managed to escape the tsunami.

40 minutes after the earthquake occurred.

The videos show how the tsunami, taking a new form,

continued to attack the city.

A ferocious backwash had begun to sweep the city.

Around this time, a video captured the image of a car

that had been lifted up onto a bridge.

The driver of the car was Yoshiki Hasegawa.

He had been swept away by the tsunami,

but came to rest on the bridge by chance, and survived.

He witnessed the ferocity of the backwash

from that vantage point.

Now, houses and cars that had been swallowed by the tsunami

were being pulled out to sea all at once.

The backwash was so powerful

that it swept a large cargo ship along in its path.

At this time, the backwash was sweeping a man and his car

down the river and out to sea.

It was Tsuyoshi Sawada.

He had given up hope of surviving

the tremendous rush of the water.

Tsuyoshi was swept helplessly along,

unable to do anything to rescue himself.

At that moment, the bridge came into view.

He could see a man on the bridge,

and he started yelling for help.

Yoshiki Hasegawa was the man on the bridge.

This video captured the moment that Tsuyoshi was rescued.

He is wearing a light blue jacket.

Yoshiki is pulling him to safety.

(dog barking)

The two men were saved by a series of chance occurrences.

But the powerful backwash of the tsunami

dragged many people out to sea.

These images show

the massive tsunami

as it came ashore in the northern part of Tohoku.

The sheer wall of the wave sent up ferocious plumes of water

as it crashed into the shoreline.

(people yelling)

The height and destructive power of the tsunami

devastated the towns along the shore.

How was such a massive tsunami created in the first place?

This is a GPS buoy that is positioned

20 kilometers off the shore of Kamaishi.

It recorded in detail the rise in sea levels

caused by the tsunami.

Changes in the sea level began

immediately after the earthquake occurred.

The sea level began to rise gradually.

20 minutes after the earthquake,

the sea level had risen two meters.

Just after that, a startling phenomenon occurred.

The sea level rose dramatically

and quickly reached seven meters.

The tsunami took the shape of a sheer, steep wall.

This rapid transformation had never been observed before.

Up until now, it was believed that tsunami were caused

by the following mechanism.

Off the coast of Tohoku, the oceanic tectonic plate

thrusts under the continental plate.

Stress builds up in the continental plate

until it snaps,

lifting the seawater above to form a tsunami.

But this would form a gently rising tsunami,

not one that suddenly rose in height.

Why was it that the tsunami took the shape of a sheer wall?

Yoshihiro Ito of Tohoku University

has offered a new hypothesis.

Ito has used underwater research vessels and other means

to survey the ocean floor

along the coast of the northern Tohoku region.

This footage was taken three years ago.

It shows how sediment has accumulated in the area

where the oceanic plate is submerging.

Ito believes this stratum of hardened mud

might have been the reason the tsunami became so massive.

His surveys have confirmed

that there is a hard layer of sediment

several kilometers thick above the plates.

The internal structure of that stratum has also been clarified.

Many faults called splay faults,

extending from the plate borders,

have been found within the stratum of sediment.

Ito postulates that this mechanism created

the massive tsunami.

The continental plate snaps,

creating a two-meter-high tsunami.

The energy of the plate movement is transmitted

to the stratum of sediment,

causing a large vertical movement in the splay faults.

As a result, the sea level above the stratum rises

and a seven-meter-high sheer wall of a tsunami is created.

The tsunami that was measured at seven meters offshore

more than doubled in height as it approached the shoreline.

(people yelling)

The massive tsunami was more than 20 meters high

when it reached the northern shores of the Tohoku region.

The increased height of the tsunami resulted in destruction

that far surpassed expectations.

Reinforced concrete and steel frame buildings

that were considered likely to survive a tsunami

were destroyed, one after another.

Why was the tsunami so destructive?

Clues were discovered in video footage of the tsunami.

This is the city of Kuji on the coast north of Kamaishi.

A sewage processing plant, the white building,

was struck directly by the tsunami.

Taro Arikawa, of the Port and Airport Research Institute,

came to Kuji to survey this building.

A 15-centimeter-thick reinforced concrete wall

was destroyed by the tsunami.

It had vanished.

Arikawa's attention was drawn

to the white portion at the tip of the tsunami

just before it hit the building.

This is a phenomenon called a supercritical flow,

which occurs when a tsunami crashes.

It only occurs when waves are very high,

and it has rarely been seen in Japan.

How much destructive power does a supercritical flow have?

An experiment was conducted in a large apparatus

called a wave flume.

This is a simulation of a 2.5-meter-high tsunami.

The front of the tsunami crashes and becomes a supercritical flow

as it nears shallow water along the coast.

Sea water falls from a high position,

and the speed of the flow triples in an instant.

The destructive force of the tip of the wave

increases in proportion to the height of the incoming wave.

The force of a 2.5-meter tsunami was measured

at 14 tons per square meter.

This is strong enough to destroy a concrete wall.

The massive tsunami hit the northern part of Tohoku

with ferocious strength.

In the flatlands in the southern part of Tohoku,

it caused a very different kind of devastation.

In this region of relatively flat plains,

a tsunami was not predicted

to spread more than a kilometer from the sea.

However, on March 11,

the tsunami reached more than five kilometers inland

and flooded a wide expanse of terrain.

This video shows the Sendai Plain

about an hour after the earthquake occurred.

The black water appears to crawl across the land.

It proceeds without cease,

swallowing up houses and fields in its path.

In this area,

the tsunami reached a full six kilometers inland from the sea.

Why did the tsunami reach such a distance inland?

Ikuo Abe, of Fuji Tokoha University,

has performed simulations of the tsunami

that attacked the Sendai Plain,

using measurements that were made throughout the area.

During the earthquake,

the hypocenter region where the plate snapped

covered an area 450 kilometers north-south

and 200 kilometers east-west.

The earthquake caused upheavals in the sea level

across a wide stretch of the ocean.

Offshore of the northern part of the Tohoku region,

the earthquake created the towering, sheer tsunami

that struck Kamaishi.

To the south, off the coast of Miyagi Prefecture

and the southern Tohoku region,

the sea level swelled into several massive, wide tsunami.

The sheer tsunami and the wide tsunami

overlapped in Sendai Bay,

and the reinforced, powerful wave headed for the plain.

About one hour after the earthquake occurred,

the tsunami reached the Sendai Plain.

It pressed inland for about 20 minutes,

with massive amounts of seawater flooding deep into the plain.

The town of Yuriage in Miyagi Prefecture

was flooded by the tsunami deep inland.

Residents cannot see the ocean from the town,

and many were not aware of the tsunami

until it appeared before their eyes.

This residential district is one kilometer from the sea.

Naoki Ishikawa, a university student,

came outside his house with his family after the earthquake.

The earthquake had knocked out electricity in the area.

The family could not watch the news on television,

and they did not hear the emergency announcements outside.

Naoki was alerted to the tsunami by the shouts of his father.

Naoki immediately ran up to the second floor of his house.

Naoki's house was swept away by the tsunami,

but he managed to cling to the roof and thus survived.

But his parents and sister, who were also at home, perished.

There is no high ground in Yuriage.

There were four designated evacuation sites,

including the elementary school.

At the sites, a considerable distance from the ocean,

there was confusion about the tsunami warning.

This is the Yuriage Elementary School,

the evacuation site furthest from the shore.

After the tsunami warning was issued,

the children took shelter

on the third floor of the school building.

Akiko Tanno came to the school to pick up her daughter,

who is in first grade.

She then took shelter at the school.

Electricity was out at the school,

and the tsunami warning announcement could not be heard.

The only sources of information for the assembled parents

were the radio and TV reception on their cell phones.

Just after the earthquake hit, the Japan Meteorological Agency

announced that the tsunami would reach Miyagi Prefecture

at 3:00 p.m.

However, 30 minutes after the predicted time

of the tsunami's arrival,

there was no sign of a tsunami in the vicinity of the school.

Teachers and parents began to feel a sense of relief

that the tsunami was not going to hit the area of the school.

Children and their parents began to go down

from the third-floor shelter to the gymnasium.

In fact, the tsunami reached shore

in the northern end of Miyagi Prefecture

at the predicted time, around 3:00 p.m.

It then headed across Sendai Bay toward Yuriage.

The tsunami reached the shore just about the time

the children had finished moving down into the gym.

This bridge is about 800 meters from the school.

A policeman was seen standing on the bridge.

He was responding to a traffic accident that occurred

because of the earthquake

when he was surrounded by the tsunami.

This photograph was taken by Hideo Moriya

near the school around that time.

The tsunami is not visible, but there is smoke rising

from the residential district.

After a short while, the tsunami appeared,

carrying tons of debris in its path.

Hideo quickly ran to take shelter in a building.

More than an hour after the earthquake,

the tsunami approached the elementary school.

At that moment, one of the parents realized

the tsunami was coming.

Michiru Kusaka happened to be

on the second floor of the school,

and she sighted the tsunami.

There were more than 100 children and parents

in the gymnasium.

Hearing Michiru's warning,

parents grabbed their children's hands and rushed for the exit.

(shouting)

This video was taken from the school building.

The tsunami flooded the spacious schoolyard in an instant.

Water flooded from the schoolyard into the gymnasium

just after the children had all fled to safety.

The children and parents had climbed

to the roof of the school building.

Their lives had been endangered by conflicting information

about the tsunami warning.

All of the designated evacuation sites in Yuriage

were flooded by the tsunami.

Having lost their refuge,

people headed for an expressway three kilometers from the ocean.

The expressway is eight meters higher

than the surrounding area,

and is the only high ground in the district.

Kazuhiro Numata was one of those who headed for the highway.

He loaded his daughter and his elderly mother in his car.

He could see the tsunami in his rearview mirror.

However, the expressway was being inspected

for earthquake damage, and the entrance was closed,

causing a traffic jam.

Some people got out of their cars

and scrambled up the hillside.

Kazuhiro finally made it to the vicinity of the highway.

The tsunami was now just behind his car.

He made a quick decision

and crashed through the toll booth gate

and up onto the highway.

The massive tsunami struck

the northern coast of Tohoku and the southern region

in different but equally devastating ways.

The number of the dead and missing

totaled more than 24,000.

Those who survived that harrowing day

shared their thoughts with us.

Yoshiki Hasegawa,

who was in his car when it was swept away by the tsunami.

Coming to rest on a bridge, he managed to survive

but saw many people in houses swept out to sea.

Akiko Tanno came to the elementary school

to pick up her daughter.

She now regrets leaving a safe spot,

despite the fact

that a tsunami warning was in effect.

Saeko Kudo, who was swallowed by the tsunami

along with her mother.

Saeko knows people have many reasons

for failing to take shelter, thinking,

"This city is prepared for a tsunami,"

or, "My parents are elderly."

These thoughts must be replaced

with a strong determination to escape.

Saeko agreed to be interviewed

because she wanted to convey this message.

How can we build upon the experiences

of people who survived that day,

so that those sacrifices will not be repeated?

In order to protect precious lives,

it is incumbent on each of us to answer this question.

The exploration continues on NOVA's website,

where you can watch any part of this program again.

Examine the deadliest tsunamis of the past

and discover where the next big one could strike

and what we can do to prepare for it.

Dig deeper into Planet Earth

with expert interviews, interactives,

teacher resources and more.

Follow NOVA on Facebook and Twitter

and find us online at PBS.org.

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