It's Sunday morning, on a paradise island in Asia,
home to 40 million people.
Just off shore, lies one of the largest geological faults on the planet.
Scientists have been studying it for decades,
hoping to understand its seismic behavior.
Then, the biggest quake for 40 years rocks the region.
Next, a horror no one had foreseen
claims over a quarter of a million lives.
It was so surprise, it was so devastating,
because it's act of god.
It went from a perfect day in paradise to this horrific day in a matter of seconds.
The experts are bewildered by a series of bizarre phenomenon.
Freak waves destroy entire communities.
The megatsunami in 2004 is the greatest mystery we have yet to unravel.
Using cutting-edge scientific analysis,
they shed new light on what really happened
and reveal that tsunamis are more of a threat
than the world ever realized.
Disasters don't just happen.
They're a chain of critical events.
Unravel the clues
and countdown those final seconds from disaster.
SECONDS FROM DISASTER by chochancuuDuc (hdvietnam)
ASIAN TSUNAMI.
The Indian Ocean, the third-largest in the world.
On its Eastern boundary, lies a massive trench
formed at the edge of a vast fault line known as the Sunda Megathrust.
Here, two of the world's giant tectonic plates collide.
American geologist Kerry Sieh
has been studying the fault for the last 10 years.
The plates are the biggest moving objects on the planet.
The Indian plate is dying down beneath the Asian plate.
And the overriding plate is dragged down with it.
This collision zone is a breeding ground for earthquakes.
And while the Northern end of the fault has seen little major activities for at least 500 years,
the Southern end is a different story.
Here, a bigger earthquake is thought to happen about once every 2 centuries.
The last one was from 1833,
so almost 200 years ago.
We get all nervous that sometimes in the next minute to next 30 years,
that part of the megathrust might break again.
The megathrust is well-known to geologists.
But for most people who live, work and play around this vast body of water,
the potential dangers were unknown.
In the last days of 2004,
all that would change forever.
A jewel of the region is the Thai island of Ko Phi Phi.
More than 150,000 tourists every year
come to experience the dramatic scenery and glorious beaches.
25th the December, 2004.
The Moore family from California are having a vacation of a lifetime.
It was our first time in Asia,
and the island was like no other place I've ever been to before.
Your paradise.
Ken's been videoing his wife Gaylene
and their daughters Kendra aged 8 and Danielle aged 6
as they enjoy their tropical Christmas.
With my kids being 6 and 8,
the best thing about Christmas was they had a big party.
Our children were having a good time.
Thailand is just one of more than 60 countries that surround the Indian Ocean.
460 kilometers away is the politically-troubled island of Sumatra.
On its West coast, lies the community of Lhokgna.
Despite more than 2 decades of civil unrest in this Northern part of the island,
Lhokgna manages to maintain an easy-going normality.
Its population of 15000
cramped along a narrow strip of land between hills and the ocean.
December 26th.
It's 7:57 am.
Ibu Nurleilly hangs up the family washing
while 3 of her children eat their breakfast inside the house, watching TV.
We live near the ocean,
this morning there's nothing unusual,
no wind, clear blue sky.
The youngest of Ibu's children is 9-year-old Ichut.
She is a bright and thoughtful girl
and likes to help her mother with the chores.
Ichut has a 16-year-old brother and a 17-year-old brother called Fitri.
She has been blind since birth
but has become an expert seamstress,
took a delight of her mother.
Even that she's blind,
she's very talented in selling her embroidery.
She makes them and designs.
Ibu has recently lost her husband
and her children are all she has left.
7:59.
Deep beneath the ocean, the earth begins to shake.
The tremors continue for more than 8 minutes.
Ibu and her kids are terrified by the violence of the shaking.
We stay in front of our house, just praying or sitting in front of our house.
8:15 am.
A vast wave hurtles towards the Sumatra coastline.
8:16 am.
The quake is over,
and families all over the region try to take stock of what has happened.
28-year-old streets trader Samsul Kamal surveys the damage.
When he looks towards the ocean,
what he sees baffles him:
an expensive exposed sea bed.
And he senses danger.
I know if the sea goes out that far,
it will come back again.
Then, in the distance, Samsul spots a terrifying wall of water approaching fast.
Within moments, Lhokgna is swamped by a maelstrom of turbulent water.
A second wave thunders towards Ibu and her family.
This one is much higher and towers over the trees.
We see the water, it's as high as a mountain.
Ibu tries desperately to hold on to Ichut.
But the little girl is torn from her hands.
On top of a nearby hill,
Samsul watches as a third, even bigger wave approaches.
Although he's 35 meters up,
a mighty wave almost kills him.
A third wave went right over my head.
13 kilometers North, lies Banda Aceh,
the provincial capital
and home to 300,000 people.
8:40am.
In the city center, 4 kilometers inland,
an amateur cameraman films the aftermath of the quake.
It captures this footage, as sea water rolls slowly up the street.
Suddenly, the flow accelerates.
Within seconds,
the water is moving faster than a man can run.
As chaos unfolds in Sumatra,
the tsunami continues its journey eastwards.
On the holiday island of Ko Phi Phi,
the Moore family prepare to leave their resort after a memorable visit.
Being it was a Christmas the night before,
we were up late,
and we just took an usual breakfast.
And I'm thinking only about half an hour we need to check out.
In their hotel room on the third floor,
mom Gaylene and girls Kendra and Danielle
are relaxing before finishing their packet.
My wife, all of a sudden, said "Honey, look, grab your camera!".
Ken sees that the pool area has been swamped.
At first, I just thought it was just a little tidal surge.
Until I looked farther, out in the bay, and realized there was a 20-foot wave, coming at the beach.
I surf, so I knew this wave had a potential to knock the hotel out.
We were trying the get the kids back away from the window,
the kids away came through the window.
Ken knows that they are in a dire situation.
I was beginning to lose it,
and my wife said "No, we can't do that, we've got to be strong for the kids".
While people fight for their lives in the Eastern Indian Ocean,
2000 kilometers to the West, in Sri Lanka,
the Squire family from England
have been spending Christmas on the housing beaches of Arugam Bay in the East of the Island.
We knew it's one of the last family holidays
that we'll probably be having,
as the children are getting bigger.
Louise and Phill have 3 children:
16-year-old Will,
Laura, who's 18, and their eldest, Emma.
Today is Emma's 20th birthday.
Louise and Phill arrange to meet Emma at the beach front dining area.
But first, Emma heads for the bathroom to freshen up.
As Louise waits for her daughter,
she notices that water is seeping into them.
The floor of the restaurant begins to flood with water.
When she looks up, she sees a wide brown surge of water heading straight for her.
Something tells me this is incredibly life-threatening.
Louise immediately thinks of Emma,
knowing she will be totally unaware of the looming threat.
There are just seconds in which to act,
seconds which could spell the difference between life and death.
On the Asian island of Sri Lanka,
holiday maker Louise Squire sees the terrifying sight of an approaching tsunami.
Her daughter Emma is unaware of the danger.
Tons of water explode into the room.
Within seconds, Emma is trapped
and running out of time.
Incredible currents begin to tear the resort to pieces
and Louise is swept away.
The next thing I remember, I'm just under a huge amount of water,
and I'm thinking, this would be so easy to die.
Louise drags herself to safety.
I remember thinking where are my children
but knowing there was nothing I could do.
Over the next 2 hours,
a series of waves swamp Arugam Bay.
Eventually, the water recedes,
revealing the terrible scene.
I see a completely-devastated damage.
Unable to find her family,
Louis makes her way to the highest point on the island,
her last and only hope of finding them alive.
But even here, there is no sign of her children or husband,
and she begins to despair.
I start planning my own exit from the world.
But then, she hears familiar voices.
Mom!
Phill comes through the garden, and followed by Emma, Laura and Will.
And it was just unbelievable.
And we just hugged each other.
It's amazing,
she just kept on the piecing, I thought I lost she. I thought I lost she.
We were in tears.
We couldn't believe our luck
or how all 5 of us could have survived.
The tsunami continues on its devastating path,
finally bringing chaos to the coast of Somalia in Africa,
5000 kilometers from its first landfall.
Even here, the waves kill 289.
All across the Indian Ocean,
incredible events have been captured on video.
In Thailand, astonished holiday makers filmed an exposed sea bed,
the water drained from the beach, followed minutes later by a vertical wall of water.
3000 kilometers to the Southwest,
the Maldives, a low-lying island chain, are all but submerged.
To the North, in Sri Lanka,
a shopkeeper films the plight of school girls trapped in what was a bus station.
Back home Ko Phi Phi,
Ken Moore and his family
face a shocking new reality as the flooding subsides.
The people in that bay were gone.
We've been out, there's snorkelling, swimming a day before,
and this wave just came and picked everyone out there, just washed them away.
There was people with horrific injuries,
I mean broken arms and legs twisted in lacerations,
sheets covered the people that were dead.
On Sumatra, the coastline is now unrecognizable.
Ibu Nurleilly desperately searches for her children.
After the water receded, I was confused and frightened.
There's so many dead bodies.
Not only people from this village,
the people from other places too.
Ibu finds her blind daughter Fitri,
then her son.
Together they look for the little 9 year old, sifting through debris and corpses.
But it's a race against time.
With each passing minute,
their chances of finding Ichut alive are dwindled.
We look for Ichut everywhere.
But after hours of fruitless searching,
the awful truth is inescapable.
I couldn't find my little one.
I haven't seen Ichut to this day.
Like so many youngsters,
Ichut was not strong enough to survive the water.
At least 1/3 of the tsunami's victims are children.
This is the most devastating tsunami in recorded history.
Entire communities are erased.
The scale of the disaster shocks the world into action.
And an international relief begins.
But for many, it is too late.
Sumatra alone loses around 170,000 people.
In total, more than 270,000 people are killed,
but the true death toll will never be known.
But what could have happened?
What kind of tsunami can create super-high waves,
retreating oceans and devastating debris flow?
And the most important of all, is there anything
we can learn to prevent such a catastrophe from happening again.
Fully understanding this complex disaster
requires expertise from many different disciplines.
And a team of world class specialists come together to investigate.
For earthquake expert Kerry Sieh,
this event raises conflicting emotions.
It's quite a schizophrenic experience,
you have not only your scientific acceleration,
but you also have this that powerful enough to do a lot of damage to people.
Professor Costas Synolakis is head of the Tsunami Research Center in California.
and investigator for 30 years,
he's analyzed about 20 freak waves in 10 different countries.
Our work is very much like
the FBI profiling a serial killer.
We have to very very carefully look at the clues, then
we can maybe point our finger and say this is where the killer came from
and this is what he can do again.
Synolakis is an expert in modelling tsunamis.
He tries to predict what would happen to low-lying coastal community such as his own in Southern California,
if they were hit by a wave at a certain size.
And he advises where to locate public buildings, like hospitals,
to avoid being swamped in an emergency.
The Asian event perfectly illustrates the need for this kind of research.
Tsunamis, they're inevitable.
It's just a question of time.
George Plafker is a pioneer of tsunami science.
and has been studying them since the 1960s.
Even he is stunned by the images coming in from all around the Indian Ocean.
What was really surprising was the size of the tsunami,
and I just struck it, and how deadly it was.
For all the experts,
there are some particularly-troubling aspects of the disaster.
The first is the unprecedented size and savageness of the waves.
Reports are coming in
that in Banda Aceh, the destruction reaches as far as 4 kilometers inland.
The second puzzle
is the extraordinary range of the devastation.
For a tsunami to cause chaos
from Thailand to Africa, across 6000 kilometers of ocean,
about 1/7 of the Earth's circumference,
the energy required is scarcely credible.
What happened was beyond the scenario we had ever seen or imagined ever before.
As the disaster unfolds,
the media is in no doubt as to what created this giant tsunami.
An earthquake that rocks Sumatra
just minutes before the killer waves arrived.
The experts have to agree.
But as early seismic data comes in,
the size of the tremors is confusing.
First reports indicate a quake measuring 8 on the Richter scale.
This is strange.
Now, you put this into perspective,
we see a magnitude 8 earthquake somewhere around the world, maybe once every 2 years.
A relatively-common magnitude 8 quake
is not powerful enough to produce the devastation scene.
Then, as a monitoring station revise and analyze their data,
the estimate steadily increases.
By the afternoon,
a station in Colorado puts the quake at 8.5.
If that's the size, it would be the biggest earthquake in more than a decade.
By the end of the day,
data from around the world confirms that the quake lasted an unprecedented 8 minutes
and released so much energy that strictly speaking it is off the Richter scale.
By that point we knew it was the biggest earthquake in 40 years.
The seismic data throws up another surprise:
it seems that the origin of the quake was 30 kilometers below the surface,
150 kilometers off Sumatra,
paradoxically, in the Northern section of the Sunda Megathrust,
the part long thought to be virtually dormant.
Seismologists calculate that the megathrust
probably ruptured along an astonishing 400 kilometers of the fault,
a long thin stretch of ocean floor
seems to have risen in a matter of seconds.
Synolakis is all too aware of what could have happened next.
As the sea floor moves up, it lifts with it a column of water,
displacing billions of tons of liquid,
causing a wall of water to move away on a either side.
To prove this scenario,
Synolakis feeds the data into the most powerful tool he had:
specialized tsunami predictions software.
But Synolakis is perplexed by the outcome of the simulation.
The software predicts that the biggest wave from a 400 kilometer rupture
wouldn't even hit Sri Lanka,
in reality one of the most devastating coastlines.
This just doesn't make sense.
The damage in Sri Lanka is a huge clue.
For the tsunami to have hit Sri Lanka,
the earthquake fault zone has to be way longer.
Synolakis takes stock.
He decides to revisit the seismic data.
He knows from experience that seismic measurements recorded during a large quake
do not always accurately reveal the true length of the earthquake zone.
The sheer intensity of the main event can mask smaller movements further out along the fault.
Often, the best way to discover the truth
is to look at the aftershocks that follow the first cataclysmic release of energy.
These smaller tremors are caused as the fault settles down
and can be pinpointed with greater accuracy.
As Synolakis scans the data,
he notices a flurry of tectonic activity way to the North of the epicenter.
It's a decisive moment.
If this activity marked the Northern limit of the rupture,
it would stretch a staggering 1600 kilometers,
four times longer than has been throught.
A rupture on this scale would be unprecedented,
enough even to cause the killer tsunami.
But the aftershock evidence is circumstantial.
Synolakis needs some real proofs.
If this fault has unzipped for such a huge distance,
somewhere along its length, there should be evidence.
Synolakis knows that Kerry Sieh is already on the ground in Indonesia,
and ready to help.
Although much of the fault line lies beneath the water,
it breaks the surface along its length, in the form of a chain of volcanic islands.
Sieh hires a helicopter and flies North along these islands,
looking for signs of recent seismic upheaval.
As he approaches the island of Simeulue, he sees something that catches his eye:
a ghostly ribbon runs along one side of the island,
a reef that seems distinctly out of place.
I realize this island has come up, out of the water
and the entire reef is now exposed, and dead.
Sieh starts to measure how far the reef has been lifted from the water.
By comparing the heights of the up-lifted corals all around the island,
he can discover the precise movement at the Earth's crust.
The first measured 57 centimers uplift,
the further North became a meter,
further North a meter and a half.
The pattern of movement suggests that the Western side of the island has been raised by 1.5 meters.
It's incredible evidence.
The tilted island marks the beginning of the tear in the Earth's crust.
We know we had nailed down the South end of the source of the earthquake and the tsunami.
A similar survey of the island dotted along the megathrust
could give Sieh the evidence he needs to plot the true length of the rupture.
But at this critical moment,
the investigation receives a body blow.
Sieh hears that political turmoil on the islands to the North
means he can go no further.
If the length of the rupture remains a mystery,
investigators will never get to the truth of why this quake shattered expectations
to create the most notorious megatsunami in history.
Investigators are on the verge of discovering why the December tsunami was so deadly over such a wide area.
Kerry Sieh has located the start of the earthquake rupture,
but he desperately needs how far North it stretches.
Would I know more about that blow on the sea floor?
Was it 1000 kilometers long?
Was it 1600 kilometers long?
But with the helicopter survey ruled out,
how would he precede?
Then, out of the blue, one of Sieh's assistants has a brain wave:
if the dramatic physical evidence Kerry has witnessed on one island can be seen from the air,
then why not from space?
He tracks down a satellite image of an island prior to the earthquake
and just opposes it with an image taken afterwards.
Comparing these images provides a breakthrough.
The outline of the island has altered, as a result of being tilted in the water.
He also sees that the color of the surrounding ocean has been certainly transformed
due to the changing water depth after the quake.
Sieh realizes that it's possible
to work out the vertical movement of the sea bed from these observations.
This is the first time satellite images have ever been used in this way.
The team systematically analyze
images of other islands along the Megathrust
and calculate the amount of movement on the sea bed.
This audacious analysis reveals that the rupture is as long as expected,
an incredible 1600 kilometers,
the biggest ever recorded.
A rupture of this length
should be more than enough to account for the destruction witnessed as far away as Sri Lanka.
Synolakis returns to the wave simulation program
and feeds in the precious new data.
This time, the simulation delivers a tsunami
that mimics almost exactly the distribution of real attacks.
As this California-sized chunk of the earth shifts
by up to 20 meters,
the wave it creates carries the complex imprint of the seabed.
As it moves up, the piece of sea floor, of course in model, has its own peaks and valleys,
and that creates the initial surface of the wave.
This unique pattern sets in motion a sequence of undulations
that scientists call a wave train.
In the deep ocean, each crest is no taller than 50 centimeters,
but the wave train travels at incredible speed,
up to 900 kilometers an hour,
as fast as an airliner.
Beneath the surface, a deadly column of water passes through the full depth of the ocean.
As each wave enters shallow water,
it slows down to a few tens of kilometers an hour.
The back of the wave catches up with the front
and the wave rises.
The tsunami takes shape.
The wave train simulation
correctly predicts where and when the real tsunami approached all the affected coastline,
proof that the investigators have nailed to source of the tsunami.
But the scientists now face an even bigger challenge,
an explaining of bizarre and terrifying events experienced by the victims
as the tsunami made landfall.
In Banda Aceh,
a city has been reduced to rubble for something like 4 kilometers inland.
There is nothing on record to match this.
Understanding it is vitally important,
not only for this part of Asia,
but also for low-lying coastal regions all over the world.
Why is the wave so destructive,
so far inland?
It's something, uh, unfathomable.
As soon as Synolakis and his team arrive in Banda Aceh,
they get straight to work:
surveying the damage brought on the city.
Tsunami investigations are forensic investigations.
We'd like to reconstruct what has happened.
And we pick up clues, very much like detectives on a crime scene.
There are two key dimensions they're trying to measure:
the first is the maximum height above sea level that the water reached,
known as the run-up.
The second is called inundation,
the distance that the water pushes inland.
The position of debris and water marks
reveal that the run-up
varied from an astonishing 10 meters above normal sea level near the beach,
to around 3 meters in the center of the town.
The inundation is as feared, truly amazing.
The water swept an unprecedented 4 kilometers inland.
Huge volumes of water have passed through the city.
But Synolakis knows that it's the speed of the water that does the damage.
1 cubic meter of water weighs one ton.
So for every cubic meter of water that comes in,
the water about now hundreds of thousands of cubic meters.
It's like having a car that's coming in at high speed and it's hitting you.
So, the first step in solving this riddle
is to figure out water speeds across the city.
If Synolakis can establish the time the water took to travel between known locations,
a simple calculation will give him the velocity.
But getting this information is not easy.
The first place to look would normally be eyewitness accounts of the event.
But sadly in this case, most of the witnesses are dead,
And of those that have survived, many are too traumatized to help.
Synolakis must think laterally.
As he surveys the rubbish streets,
he sees that sand and mud had been deposited right across the city,
clogging every available nook and cranny.
This is marine sediment,
sand and mud picked up offshore and carried inland.
Synolakis has an idea.
He knows that the depth of this sediment
is directly related to the water speed at that place.
If the tsunami comes in, you know, very very slow,
we expect to see, you know, more sediment close to shore,
if it comes very very fast,
we expect to see thicker sediment layers further inland.
This dirt is his speedometer.
The team carefully measure the layer of sediment deposited in key locations.
Their painstaking analysis reveals an answer that beggars belief.
The water flowed up to 20 miles an hour across most of the city.
I would have expected the wave to penetrate inland
but I have never expected this kind of speed, 20 miles per hour.
3 meters flow depth, 2 miles inland.
This just didn't make sense.
He's at a loss to explain how such huge volumes of water
can be traveling so fast, so far inland.
But then comes another vital piece of evidence:
Synolakis hears about a video
which shows the water arriving in the city center.
The piece of video is a turning point for us.
Captured on tape, the wave seems to define physics.
As it hits these streets, 4 kilometers inland,
instead of slowing down as would be expected,
the wave accelerates.
If he weren't witnessing it with his own eyes,
he'd considered this impossible.
Synolakis scans the video for clues,
rewinding the action, he focuses on a minor flooding that preceded the main torrent.
The first wave was very very slow.
You could walk away from it.
But then, he makes an observation that will radically transform the science of tsunamis.
This shallow layer of water is preparing the way for a deadly event.
The first wave provides a low-friction carpet for the following wave.
The second wave is moving on this very very thin layer of the first wave.
So, it's able to propagate much faster.
Lubricated by the wet surface,
the second wave is able to power through the streets without slowing down.
Suddenly, the second wave accelerates
and goes at a speed of 30-40 kilometers per hour.
It's an extraordinary shocking sight.
It's like being thrown in concrete mixture
with nails and hammers and screwdrivers.
This is unfortunately, how people died.
They have no chance.
It's a grim, but valuable, lesson.
To survive the tsunami in a town,
neither out-running the water nor hiding in a backstreet will help,
the only escape is to get to a solid structure and go up
as high as possible.
The difference of life and death in Aceh,
in some cases, it was the difference of the fluencies.
But as Synolakis starts to believe he's solved the mystery,
he hears reports of implausibly-large waves,
just 13 kilometers to the South, in Lhokgna.
I start hearing things that are very puzzling. The run-up they measure is huge,
in excess of 30 meters.
30 meters is 3 times more than the maximum water depth in Banda Aceh
and he has no explanation.
Synolakis asks veteran tsunami scientist George Plafker to investigate.
Based on all of my experience,
the wave for an earthquake at that magnitude
should have been about a 12-meter-high wave,
but certainly not anything near 30 meters.
Plafker meets with Samsul Kamal,
the local streets trader who climbed a hill to escape the water.
He describes 3 enormous cobra-like waves,
each one larger than the last.
A third wave went right over my head.
Plafker's team
measure the run-up at Samsul's hilltop refuge
and discover that the water reached an astonishing 35 meters above sea level,
higher than an 8-story building.
That's by far, the largest tsunami
associated with any earthquake in history.
But there is more to Samsul's story.
He's sure that the wave arrived
about 20 minutes after the quake began.
Plafker is stunned.
He knows that waves from the megathrust, 200 kilometers offshore,
would take at least half an hour to reach Lhokgna.
For a tsunami to arrive within 20 minutes,
means that a different mechanism must have been at work.
Something capable of causing massive waves to arrive far earlier than was believed possible.
It's a huge setback.
This is nothing less than throwing aspect to the going board.
This anomaly strikes right at the heart of the investigation.
But resolving it will rewrite the rules of tsunami prediction
and reveal how vulnerable hundreds of millions of people
living near an offshore fault really are.
Investigator George Plafker
has discovered that monstrous waves arrived on the West coast of Sumatra too early
to have come from the source of the main tsunami.
And the investigation is in crisis.
Plafker is under pressure to solve this paradox
and decides to go back to basics.
He knows that the waves arrived about 20 minutes after the quake began,
and he knows how fast the waves could travel through the water immediately offshore.
So, working backwards,
he calculates how far away the waves must have started their journey.
It turns out that the wave could travel a maximum at about
100 kilometers.
George consults a detailed geological map of the seafloor.
There, 110 kilometers offshore,
he sees strange features that catches attention,
distinctive folds in the seabed.
Could this be the answer?
He knows that features called "splay faults" are often found near large earthquake zones.
They're where the enormous forces find a weakness in the highly-stressed crust,
and fractures break to the surface,
many miles from the main fault itself.
Splay faults can cause a narrow section of the seafloor
to pop up in a matter of seconds.
And this can produce a distinctive short birth of high waves
just like those that flattened Lhokgna.
It's an attractive theory.
And when the computer simulation incorporates Plafker's splay fault,
the results are nothing short of spectacular.
No one beheld, it, the model has doubled the height of the wave at Lhokgna.
And it shortened the time, of course, for survival.
With a pop up fault located close to shore,
the simulated waves closely match the awesome description of eyewitnesses.
A Japanese seismic team
gives the theory extra credibility
when it detects aftershocks in exactly the area that Plafker has identified.
Although it will require further research to prove,
Plafker's explanation is a breakthrough.
But there is one final question raised by the catastrophe, that's perhaps the most important of all:
Can anything be done to alert people to the danger of an approaching tsunami?
Increasingly-sophisticated warning systems are in place across the world,
capable of detecting a tsunami as it passes through the open ocean.
But even such high-tech systems
cannot always be the perfect solution.
For 60% of the victims of the Asian tsunami,
no alert would have helped.
The coast of Sumatra is too close to the source of the waves
for a warning to have had any effect.
There was no time to react.
But in the aftermath of the disaster,
the investigators are tantalized by the possibility of an unmistakable natural warning sign:
in many places,
the ocean receded before the waves hit,
and popular wisdom now says that an exposed seabed
is the universal alert that everyone aggrades.
But Synolakis is not happy with this simple rule.
In fact, it maybe a potentially-lethal myth.
He has long held a theory about what could be happening to create these strange recessions.
As the fault ruptures,
the Easternmost section subsides, pulling a trough of water down with it, and negatives waves.
As this approaches the shore, it draws the water away
before the first crest arrives.
In this side was seafloor subsides.
What you see first is the shoreline retreating.
All the waves traveling East lead with this trough,
but in the West, the story is very different.
On the other side, where you have the seafloor uplifting,
what you're seeing moving West is a leading elevation wave, or you know, the crest up first.
Up until now,
this is being just a theory,
but Synolakis obtained evidence that confirms his hunch:
locations to the West saw no recessions,
just a rolling wall of water slamming into the shore.
It's an important finding,
but disturbing, went counter to the people's assumptions.
Sadly, there is no single foolproof indicator
of an imminent tsunami.
Finally, we can now reveal
the critical chain of events that plunged the people of the Indian Ocean into a primordial fight for survival.
Prior to 2004,
scientists identified the Southern section of a faultline off Sumatra
as a critical risk for a giant earthquake.
Then, on December the 26th,
1 minute from disaster.
A section of fault further North than expected begins to break apart,
and a weakness in the crust creates a shortcut to the surface.
8 am.
A narrow section of ocean floor, about 100 kilometers long,
pops up by more than 10 meters.
3 giant waves approach shore.
Meanwhile, the tectonic plates themselves spring apart,
displacing billions of tons of water.
The energy of the earthquake is transferred into the shifting water columns,
equivalent to more than 30,000 Hiroshima bombs.
On land, initial floodings create a low-friction surface
for later waves to glide over,
creating huge water velocity that turned debris into deadly projectiles.
The human cost is incalculable.
Almost everything that Inu Nurleilly owned has gone.
Her only photograph is a portrait of her lost daughter, Ichut.
The unexpected location of the December quake
means that every undersea fault
must now be considered a tsunami threat.
Costas Synolakis is painfully aware
that his home on the seismicly-actived West coast is inherently vulnerable.
But his experience of the Asian tsunami
has only increased his resolve to plan for that day.
Whenever we see a tsunami in the West coast of the United States,
we'll then be prepared
and hopefully, we're not going to have any human victims.
subtitle by chochancuuDuc thank you for watching this subtitle! thanks to YouTube account "Jen stalker", who helped me to find out the word that I didn't know exactly what it is.