(ominous music)
Tsunamis.
Deadly waves that can destroy a city in a matter of moments.
And until December 26th, 2004,
we knew almost nothing about them.
On that day in the Indian Ocean,
a gigantic tsunami killed 230,000 people.
Caught live on camera, this phenomenon
became visible to the world.
Seven years later, in 2011, in Fukushima,
a nuclear power plant exploded after being engulfed
by another tsunami.
In the wake of these tragedies,
scientists now rush to investigate the cause
of these devastating waves.
They need to understand them in order to save lives.
They know that tsunamis can hit every region of the planet.
And coastal developments make us more vulnerable every day.
Can this new science protect us?
(suspenseful music)
(soft ominous music)
On Friday September 28th, 2018 on the island
of Sulawesi, Indonesia, an earthquake followed
by a devastating tsunami destroyed the Bay of Palu.
Within minutes, 4,000 people lost their lives
and 79,000 others had to be evacuated.
How could such a tragedy happen again
after the 2004 tsunami that already devastated Indonesia?
Two tsunami specialists, Professor Costas Synolakis
of the University of Southern California,
and Professor Hermann Fritz
of the Georgia Institute of Technology
were sent by UNESCO and the Indonesian authorities
to investigate the causes of the tragedy.
Quite impressive to see the devastation.
We are now three weeks after the event.
And here we can kinda see why it's important
to come up as quickly as possible or at least
once the emergency's over
because a lotta bulldozing in this area already,
so a lot of evidence is already lost.
For those who know how to look,
these fields of ruins hold clues of the wave passage.
But time is running out.
The monsoon will soon wash away the remaining traces.
(soft ominous music)
Working as a tsunami scientist is very much
like being a detective on a crime scene.
There is multiple murders have taken place.
You really have to piece like in a puzzle
the sequence of events.
Did the tsunami hit first and this made
the houses collapse, or were they collapsed
because of the earthquake and the tsunami finished them off?
What were the people doing?
Why is it that some people died and some people did not?
(ominous music)
Both investigators want to understand
how the disaster unfolded.
Their goal, to trace the tsunami back to the original event
that triggered the wave.
In the small fishing town of Wani,
Costas Synolakis goes to meet the survivors.
Abdul Atik miraculously survived.
When the wave came, he was on his boat
100 meters from the shore.
There's a little boy in the boat.
Hey, hey, sir, get off the boat!
Get off the boat!
At the time of the first wave when there was
the big tremor, I went out on the deck of the boat.
Did you feel the tremors on the boat?
Yes, the boat shook because the water
had gone down and the boat was grounded.
What did he do at the time, he stayed with the boat?
Did you stay on the boat?
In front over there
I was holding on to the mast.
Oh, okay.
And then I saw the wave breaking
in the distance.
It was very fast.
In no time at all, it was next to the boat pushing us.
About how high was it?
I had time to see my house.
The top of it was almost at the same height as the boat.
Where is your house?
Over there.
The wave was about five to six meters high,
the height of my house.
(soft ominous music)
For Costas Synolakis,
this tsunami is an enigma.
How is it possible for a five-meter-high wave
to crash through here when a bay
is usually protected from tsunamis?
(soft suspenseful music)
20 kilometers south of Wani, Hermann Fritz is investigating
in the town of Palu where thousands
of people lost their lives.
With the help of two Indonesian scientists,
Hermann Fritz goes to the parking lot
of the shopping center overlooking the bay.
Show you where the exact place was--
In order to understand the dynamics
of the wave, he relies on another kind of witness:
mobile phone videos.
This is the exact spot that we saw on the video.
Here you can see the billboard.
Yes.
(speaking in foreign language)
Tsunami wave coming, people running away.
People running away.
Yeah, ooh.
And that's the second wave?
That's the second wave.
Second wave, okay.
That's the highest one.
So, now we can basically see how high the water is,
almost to the top of the billboard.
(soft ominous music)
Here the wave reached
over four meters in height.
Yeah, it's 1.6 here,
four up there.
Okay.
(man shouting in foreign language)
(soft tense music)
To trace the source of the tsunami,
Hermann Fritz needs to establish a model
of the devastating wave, determine its height
at different points in the city,
and measure how far it spread inland.
Wanna try to do some detail surveying here,
so we're gonna try to get a full 3-D scan,
and the purpose of that is so we get a 3-D space.
The LIDAR scans all the point cloud and we can see
how the waves go through it.
So, it can measure how high the wave is
at every given instance and how fast the wave
is moving across through the houses,
washing away the houses and across the street.
(soft ominous music)
Hermann Fritz tracks the wave.
Stand over here.
After submerging the parking lot,
the water penetrated deep into the city.
In this mosque, which is only 100 meters from the shore,
clues bear witness to its power.
This one's broken.
We have this grill here and we see this raft
of debris inside, so we know that the tsunami
was at least to this height of this rack.
And then up here we see the actual primary tsunami line,
which is this one right here, and we can also see
in the window, if you look at the blue sky,
we actually see a mud line going through there.
And then we look at that over here,
we also see the mud line coming around,
coming around, coming around.
So, the tsunami's coming pretty much
at the height of my head through this mosque,
and that's also a very difficult height already
because usually when the water is to this height,
you can not stand anymore.
You will be thrown to the ground by the water,
so it can be difficult to survive.
(townspeople shouting)
(soft ominous music)
After three days of fieldwork,
the two American researchers and their Indonesian colleagues
are finally able to produce a first simulation
of the tsunami that submerged the Bay of Palu.
(tense music)
According to their observations,
the most powerful wave spread more than 300 meters inland.
But for Costas Synolakis and Hermann Fritz,
the investigation has only just begun.
They now have to identify the event that triggered
this murderous wave and determine how
it could've swept into the bay.
Tsu, the port, nami, the waves.
The waves that destroy the port.
(suspenseful music)
This word, now universal, dates from the 17th century.
It comes from the other place on the planet
most frequently affected by tsunamis, Japan.
It was coined by fisherman who returned
on a storm-free day to discover their port
completely devastated by the waves.
The most recent tsunami in Japan in 2011
caused the nuclear accident in Fukushima.
Following a 9.1-magnitude earthquake,
the devastating wave killed more than 18,000 people.
(soft ominous music)
A tsunami has no meteorological cause.
The primary cause of tsunamis are earthquakes
and earthquakes at sea.
The vast majority of tsunamis
are generated by the planet's tectonic activity.
The Earth's crust is broken up into several large plates.
Magma pushes them against one another
a few millimeters to a few centimeters a year.
The oceanic plates slide beneath the continental plates
forming subduction zones.
Friction between the plates causes deformation
of the continental plate, which accumulates
a gigantic amount of energy.
When the tension is released,
it generates a huge undersea earthquake.
The earthquake displaces
all the water at once.
So, if we are four kilometers deep,
we have 4,000 meters of water that moves
at the speed of an airliner.
Very quickly as we approach the coast,
the speed is reduced, the wave gets bigger,
and we find ourselves on the coast with waves
of 20 to 30 meters as we saw in 2011.
You can not separate earthquake science
and tsunami science.
Longer the duration of the earthquake,
it's a very good indication of how strong is the earthquake.
It's basically it's like a zipper.
If you have a small earthquake, it's a short rupture area.
And that means the duration is shorter.
If it's a big earthquake like Sumatra, magnitude 9,
or Japan, magnitude 9 plus events,
then basically you have a very long zipper.
That means the shaking will go on for several minutes.
(group shouting)
Jesus Christ, look at that.
Jesus Christ.
Fuckin' hell.
Hell!
That wave.
Oh my God!
It's a good 15, 20 feet tall, easy.
The longer and more intense
the undersea earthquake, the more powerful
the tsunami it generates.
This is what happened during the terrible earthquake
of December 26th, 2004.
In the Indian Ocean, a fault located 100 kilometers
off the coast of the town of Banda Aceh
on the island of Sumatra, Indonesia,
broke on a line of 1200 kilometers.
The earthquake with an exceptional magnitude
of 9.1 lasted more than five minutes.
15 minutes later, 35-meter waves hit the coast.
Continuing across the entire Indian Ocean,
the tsunami claimed a total of 230,000 lives.
A huge human disaster captured live for the first time
by hundreds of video cameras.
This disaster revealed the devastating power
of tsunamis to the whole world.
Before it, little was known about these deadly waves.
For the scientific community, it is a wake-up call.
It energized the science of tsunamis,
which until then, was in its infancy.
(soft somber music)
Numerous international studies are launched.
The research of Indonesian geologist Nazli Ismail
will lead to a major revelation.
(Nazli speaking in foreign language)
Here, the tsunami reached 30 meters high
up to the top of the hill over there.
People rushed to the mountains, but very few survived.
Surveying the coast for traces of the tsunami,
Nazli Ismail made an exceptional discovery
30 kilometers south of Banda Aceh.
After the 2004 tsunami,
this cave was full of debris, full of pieces of wood.
(worker speaking in foreign language)
This cave has a very particular architecture.
It is L-shaped and its entrance is parallel to the coast.
So every time the water of a tsunami
comes to submerge this cave, it is retained inside.
(soft ominous music)
Nazli Ismail had a hunch.
If this cave trapped the material carried
by the 2004 tsunami, it could also hold
the memory of past catastrophes.
(bats chirping)
The cave had another particularity: bats.
They have colonized it for millennia.
Each tsunami is covered by a layer of guano.
You can see the layers of guano in black here.
Over the years, layers of guano,
or bat droppings, deposited between each tsunami
have become fossilized.
They mark a clear boundary that delineates each event.
A layer of tsunami, then a layer of guano.
A layer of tsunami and more guano.
Then a tsunami, then more guano.
Tsunami then guano, and the 2004 tsunami.
With the help of researchers
from Singapore's Earth Observatory,
Nazli Ismail is able to date 12 deposits by carbon-14.
They tell the story of tsunamis in this region
over the last 10,000 years.
(soft ominous music)
The upper deposit corresponds to the 2004 tsunami.
The next event is about 2,900 years earlier.
Then, four tsunamis occurred 25 years apart,
about 3,300 years ago.
The oldest was about 7,500 years ago.
From the data obtained here,
we have discovered that tsunamis are recurring irregularly.
This is a lesson for both the government and the people.
We have to be vigilant, to be constantly ready
because this disaster can happen at any time.
(children chattering)
This exceptional discovery is a game-changer.
Now, scientists know that where a tsunami
has once struck, another can strike again.
(suspenseful music)
Now the question is,
where have tsunamis occurred in the past?
(soft suspenseful music)
Since 2008, UNESCO has kept a worldwide tsunami map,
updated with scientists' latest discoveries.
Over the past three millennia, 1200 tsunamis
have been confirmed.
The least destructive are in white
and the most deadly in red.
Any one of them might become a potential tsunami
in the future.
(radar beeping)
70% of tsunamis are located along the Pacific Ring of Fire
where subduction zones are concentrated.
But they have occurred elsewhere on the planet,
particularly in a region thought to be spared
of this kind of disaster, the Mediterranean.
(suspenseful music)
In Nice, thousands of tourists
enjoy the pleasures of the beach.
But a stone's throw away, a team of scientists
from the Geoazur Laboratory are in search
of the cause of a forgotten disaster.
(soft tense music)
Digging through regional archives,
researchers discovered that on February 23rd, 1887,
an earthquake followed by a two-meter high tsunami
hit the coasts of France and Italy.
From Nice to Genoa, 600 died and tens of thousands
lost their homes.
Today, two million people live along the Riviera.
Can such a disaster happen again?
Geoazur's scientific team is looking for the fault
at the source of the 1887 earthquake
to assess its condition.
Two Italian scientists,
Taramelli and Mercalli, recorded at the time
in a very precise way, all the destruction
that happened on the coast.
We have 2700 observation points between France and Italy.
(soft ominous music)
Christophe Larroque and his team
use these photographs taken at the time of the disaster
to establish a map of the earthquake's intensity.
The more important the damage, the closer the source.
It led them to locate its epicenter
off the coast of Imperia.
But identifying the exact fault responsible
for the tsunami is a delicate task
because this seismic zone is one
of the most complex in the world.
The African Plate in the south rises toward
the Eurasian Plate in the north,
pushing Corsica and Sardinia against the Riviera,
generating numerous seismic faults.
How can the fault responsible
for the 1887 tsunami be identified?
We're using sophisticated
seismic investigation equipment
which consists essentially of cannons
which are a source of waves,
which will permit us to obtain a sonogram
of the inside of the Earth up to 15 kilometers deep.
These waves will be recorded by the sensors we have
within the line, a line that is six-kilometers long,
dragged behind the boat.
After five days at sea,
the ultrasound reveals not one,
but three faults below the seafloor.
Their location, 30 kilometers from the coast,
corresponds to the epicenter of the 1887 earthquake.
The morphology of the faults suggests
that they are still active and allows the scientists
to model two possible tsunami scenarios.
The first scenario is an earthquake
equivalent to that of 1887 with a 6.7 magnitude,
which would break a fault length of about 30 kilometers
with wave heights of two meters.
(soft ominous music)
The second extreme scenario is to envisage a rupture
over almost the entire length of the fault,
for example 60 to 80 kilometers,
which would then produce an earthquake of magnitude 7
and wave heights that could reach three to four meters.
The Mediterranean, the world's leading
tourist destination, is at risk.
But scientists can not predict
when such an event might occur.
(boat horn bellows)
Since 2012, the region has been monitored
24 hours a day by CENALT, a tsunami warning center.
Evacuation plans have been drawn up with a focus on Nice.
But the reality remains.
The rupture of a fault located 30 kilometers
from the coast only allows a 20-minute evacuation time
before the wave breaks.
Even a small tsunami can be very devastating.
A wave breaking on the beach with the speed
of around 40 kilometers per hour
will create extremely strong currents
in which people can not swim.
Mediterranean beaches, just like many beaches
in the Indian Ocean, are very high risk.
The reason is that in the summer we're gonna have
tens of thousands of beach visitors on a beach
with the possibility of a tsunami arriving,
you know, within a few minutes.
(soft ominous music)
Coastlines are popular with locals
and tourists all over the world.
This makes tsunami warning systems all the more necessary.
(suspenseful music)
In Palu, where Costas Synolakis and Hermann Fritz
continue their investigation,
a tsunami warning system was set up after the tragedy
of 2004, so why were there so many victims 15 years later?
There were a lot of food vendors right here,
a lot of people.
There was a rumble (imitates earth rumbling) like this.
People were shouting all over the place,
"The water is rising, the water is rising!"
According to this witness,
the crowd in the streets along the beach
was completely surprised by the wave.
No alert reached this area.
(somber music)
The investigation continues at the tsunami monitoring center
in the Indonesian capital, Jakarta.
This control tower monitors seismic activity
throughout Indonesia, including the Bay of Palu.
Here, seismologists can detect any earthquake
at sea in real time.
Advanced algorithms allow them to simulate
the formation of a tsunami and warn people
before the first wave hits.
Since its implementation in 2008, 22 alerts have been issued
and countless lives have been saved.
Then why, on September 28th, 2018,
was no warning received in Palu?
That night, seismologist Kian Purna Sinki was on duty.
At the time of the earthquake in Palu,
the magnitude was 7 for two minutes,
then just afterwards the magnitude rose to 7.7.
At that time I ran to the tallest table.
It's the tsunami simulation table.
In the early evening,
an earthquake 80 kilometers north of the bay
was clearly detected by Jakarta.
The epicenter is here, Palu is there.
According to the simulation,
this earthquake presented only a moderate risk of a tsunami.
Nevertheless, an alert was triggered
within the prescribed time limit,
five minutes after the earthquake.
So, what happened?
(water roaring)
(somber music)
Java or--
Costas Synolakis will discover the answer
thanks to surveillance cameras.
Friday, September 28th at 6:02 p.m.,
the earthquake hits the Bay of Palu.
It lasts a little over a minute.
(earth rumbling)
(objects rattling)
How did you feel about the earthquake?
Was it really incredible?
You couldn't stand up?
Impossible.
I was there under camera two.
I was hanging on to the gate and then it calmed down
and I came out.
That after the earthquake,
because he's so close to the water,
perhaps a tsunami will come.
They've always said a bay is a bay,
it doesn't have tsunamis.
They always occur in the open sea.
And yet, it did happen right here.
(soft ominous music)
These images provide researchers
with crucial information: time.
The clock displayed on the videos reveals
that barely two minutes elapse between the end
of the earthquake and the onset of the tsunami.
Never before was such overpowering speed recorded.
The warning signal launched by the Jakarta control system,
was triggered after the arrival of the wave
when all communication systems
on Palu were already destroyed.
What is very alarming to me, is that here the earthquake
triggered the tsunami very quickly.
So, we need to understand how this happens
and also what is the timing.
How quickly after the earthquake hits the tsunami comes in.
According to the Jakarta center's simulation,
a wave born close to the epicenter
80 kilometers north of the bay should have taken
about 15 minutes to reach Palu, not two minutes.
(suspenseful music)
This tsunami defies all known patterns.
How could the wave arrive so quickly?
To figure it out, the researchers take to the air.
It's extremely important to us
to have a bird's-eye view of the entire place
because by being up on the air in a helicopter,
it allows us to see how this wave came in
and see the extent of the inundation.
A first observation is surprising.
Devastation alternates with untouched areas.
But that's not all.
So, once you get outside of the bay,
the wave disappears very quickly and you're lookin'
at very beautiful Indonesian beaches.
So, that already allows to confine the zone
where to look for further for the sources to inside the bay.
If the wave that devastated Palu had formed
in the ocean, the entire coast would have been hit.
For Hermann Fritz and Costas Synolakis,
the epicenter identified by the Jakarta warning center
could not have directly generated the killer wave.
The source of the tsunami must be inside the bay itself.
Hermann Fritz and his Indonesian colleague,
Gegar Prasetya, return to the west bank to understand
how the tsunami could've originated in this sheltered area.
Gegar Prasetya has collected new footage film nearby.
The barge is still over there in the same position,
so then you can see also the background of these events.
And then this is when it started this landslide.
(man shouting in foreign language)
Yeah, a local landslide, co-seismic,
triggered by the earthquake.
You have a small semi-circular wave
that you can even see in the video.
So, I think this is gonna be a localized impact
from this landslide tsunami.
You have a lot of alluvial material here,
so I think once you shake it, it will go.
(man speaking in foreign language)
For Hermann Fritz, the low intensity
of this first wave, filmed at the very moment of its birth,
suggests it was triggered by a very localized phenomenon:
a coastal landslide.
Here, we have evidence because we have a coastal scarp.
Okay, so the scarp actually is along the shoreline.
The land went into the ocean
and so we have a coastal landslide.
I don't think this localized tsunami is big enough
to be the main source of the tsunami
that wiped away Palu or Wani on the other side of the bay.
(ominous music)
Surveying the entire bay,
researchers discover several other similar landslides,
all sources of mini-tsunamis.
But it is by looking further inland
that the full story of the Palu tsunami
finally becomes clear.
Look, this is pretty amazing.
Here's the rift.
The tremors opened it, then closed it and opened it again.
A few hundred meters away,
a second witness points out the extent of the destruction.
It collapsed all the way down there,
all the way to the mosque in Icra.
All the houses collapsed at the same time
from south to north like the slope of the house.
An immense fault line cuts through the town
and then extends into the bay for tens of kilometers.
Researchers finally have the answer.
It is this fault that caused the Palu tsunami.
After five days of field investigation and months
of data analysis, the sequence of events
is finally reconstructed.
On September 28th, 2018 at 6:02 p.m.,
a 7.2 magnitude earthquake occurs
80 kilometers north of Palu.
The epicenter, correctly identified
by the Jakarta control center,
does not directly trigger the tsunami.
The seismic wave travels by land
at an extreme speed of 900 kilometers per hour,
triggering the fault that crosses the entire bay.
Within two minutes, landslides are provoked
all along the coast, generating several mini tsunamis.
The energy of all these mini tsunamis
accumulates inside the bay, combining to form
a powerful wave that sweeps across the town.
Hermann Fritz and Costas Synolakis's investigation
has come to an end.
Their reconstruction of the Bay of Palu tsunami
will help improve warning systems all over the world.
We used to think that tsunamis only strike
in areas where you have subduction zones.
We now know, just like what happened here,
that tsunamis can strike pretty much anyplace
where you can have an earthquake.
We are very concerned about this because similar earthquakes
could take place in Seattle, they could take place
in Southern California, they could take place
in the Caribbean, and they could take place
in the Mediterranean.
(soft ominous music)
What walls of water, what winds,
what thunder, what a horrible earthquake,
what a frightening sound of the sea
and what howling of a great people.
These words by the great Italian poet Petrarch
describe a strange storm over the city of Naples
in the 14th century.
It's an early testimony to man's fear in the face
of the destructive power of nature.
700 years later, the vulcanologist Mauro Rosi,
who works on emergency plans for the city of Naples,
was intrigued by Petrarch's description.
If earthquakes and fault ruptures cause most tsunamis,
volcanic eruptions can also trigger them.
Petrarch was the exceptional witness
of a phenomenon that struck the city of Naples.
He was sleeping not far from the port
when he heard strange noises so powerful
that he thought it was an earthquake.
Petrarch ran towards the port like the majority
of the population and saw with his own eyes
the port completely devastated.
Along with the destruction,
Petrarch reports hundreds of deaths
and dozens of sunken ships.
According to Mauro Rosi, this strange storm
is clearly a tsunami.
At that time, Petrarch could not have known
that it was a tsunami since they were unknown
in the Middle Ages.
Now, today, we know for sure that this phenomenon
was caused by a tsunami.
To determine if a such a tragedy
could be repeated today, the vulcanologist is looking
for the source of the tsunami that devastated
the Port of Naples in 1343.
But there is no historical account of an eruption
of Vesuvius, the famous volcano that dominates Naples
in the 14th century.
So, Mauro Rosi focuses his attention on another volcano,
one of the most active in the region, Stromboli.
But it's located 200 kilometers from Naples.
In 2002, an eruption caused the collapse
of one of its walls, generating a 10-meter high wave
all around the island.
The wave spread through the Tyrrhenian Sea,
and although very weak, reached the Bay of Naples.
Could it be that a much larger eruption on Stromboli
triggered the tsunami described by Petrarch 700 years ago?
On the slopes of the volcano, archaeologist Sara Levi
excavates the remains of a small collapsed church.
She provides Mauro Rosi with his first clues.
We know that a dramatic event occurred
due to the sudden collapse of the building,
probably caused by a powerful earthquake
because large blocks of stone were found inside
on the floor of the church.
(soft suspenseful music)
In order to date the past activity
of Stromboli, archaeologists examine three skeletons
found in the remains of the church.
This skeleton was in a grave pit that was dug
through the layer of collapsed tiles
that fell down when the church collapsed.
So, this person was definitely a witness of the catastrophe,
possibly a victim, possibly a survivor.
This skeleton has been dated by carbon-14
in the middle decades of the 14th century.
The date of the earthquake
that shook the island of Stromboli
coincides with the disaster in the Bay of Naples
described by Petrarch.
Yet another detail reveals the magnitude of the event.
When the church collapsed, it was not rebuilt,
which is surprising and indicates a major change
in human occupation at this location.
It is likely that the island was abandoned until the 1600s.
This dramatic event was so violent
that for more than 200 years, 10 generations,
the island of Stromboli remained unoccupied.
Following these revelations,
Mauro Rosi starts his own excavations.
He wants to find clues linking the activity of the volcano
to the tsunami described by Petrarch in 1343.
(soft somber music)
At a depth of more than four meters,
the volcanologist finally uncovers a fabulous deposit.
This tsunami deposit is by far
the largest we've ever found and we've dated it
to 1350 as evidenced by the materials in it.
Look at the size of these perfectly round rocks.
They must have come from the beach.
The presence of such consistent elements proves
that the tsunami was driven by an extraordinary force.
All the facts coincide.
The powerful wave that projected these rocks
200 meters from the beach occurred at precisely
the same time as the earthquake that destroyed
the small church on the island.
For Mauro Rosi, there is a clear link
between the eruption of the volcano and the tsunami.
La Sciara del Fuoco.
It is on this impressive slope that all
the volcanic material ejected by Stromboli accumulates.
700 years ago, following an eruption,
the volcanologist believes that the Sciara del Fuoco
suddenly shed its millions of tons of accumulated debris,
causing a tsunami that spread to the Bay of Naples.
Given the current activity of Stromboli,
it's assumed that the level of detritus
on the Sciara del Fuoco would be comparable
to that of the Sciara at the time Petrarch
describes the tsunami.
(eruption booms)
For Mauro Rosi, the landslide caused
by the 2019 eruption is a harbinger
of a much more serious disaster to come.
The Sciara del Fuoco could collapse
into the sea at any moment.
The island of Stromboli is monitored 24 hours a day
to alert the authorities, inhabitants, and tourists.
But what about Naples?
What would be the consequences of a tsunami
hitting a city of one million inhabitants?
The population is completely unaware
that a tsunami from Stromboli could hit Naples.
In the case of infrequent natural phenomenon,
people tend to believe that there is no imminent danger.
(soft ominous music)
Researchers at the University of Bologna
have made a model of the path of the 1343 tsunami.
It gives an idea of what could happen today.
It would take barely 30 minutes
for the tsunami to leave Stromboli
and hit the Gulf of Naples.
And here, the consequences would be unbelievable.
All the boats in the harbor behind me
would be thrown into the streets.
The water would rush into the subway
and drown its occupants.
The streets full of people would be submerged.
It would really be an apocalyptic scenario
if we weren't able to sound the alarm.
(soft ominous music)
Earthquakes, fault slides, volcanic eruptions.
All sorts of tectonic activity can trigger tsunamis.
Research carried out over the last 15 years
has made it possible to perfect warning systems
and better adapt them to each risk zone.
In Japan, a country at the forefront of tsunami science,
the technology is the most advanced.
Here, researchers know exactly where
the next disaster will come from.
(alarm blaring)
These images are not those of a disaster movie,
but a public service announcement
from the Japanese authorities broadcast in March of 2018.
It's intended to prepare the population for a tsunami
that scientists give an 80% chance of occurring
in the next 30 years.
The film explains how to react and behave, but also predicts
the likely scale of a disaster.
350,000 victims and widespread damage that would
affect the Japanese economy for at least 20 years.
The cause?
The rupture of the Nankai fault that runs
along the west coast of the country for 900 kilometers.
The threat of the Nankai Trough
is very specific because it is located
in front of all the economic centers of Japan.
Whether Tokyo, Osaka, Nagoya, all these cities
are in vulnerable areas.
No technology can predict an earthquake,
but the Japanese have set up an extensive monitoring system
to immediately warn the population.
It's a matter of listening to the fault,
knowing when it will move and being able
to sound the alarm as quickly as possible.
And for that we have the DONET system
which is just outside Osaka Bay.
The DONET system is the most sophisticated
seismic detector in the world.
29 underwater mini observatories, pressure censors,
seismometers, accelerometers are installed
directly on the fault line off the coast of Osaka
to give the alert as soon as the first tremors occur.
The tsunami would arrive
between three and five minutes in the first cities
with waves of 20 to 30 meters.
Then the wave enters Osaka Bay and floods parts of Osaka,
parts of Kobe, and especially all the islands
that have been artificially created.
Depending on the scenarios, we expect waves
of three to five meters, and that would take
between 30 and 45 minutes.
(soft ominous music)
In order to establish
the most effective evacuation plans
and test protective walls,
the disaster prevention center at Kyoto University
simulates the effects of a Nankai fault tsunami in a pool.
We're almost certain that it will be
an earthquake of at least magnitude 9.0,
and that it will cause a tsunami.
Professor Hiraishi recreates the arrival
of a wave with an average height of 20 meters,
the equivalent of a six-story building
on a city directly facing the Nankai fault.
In spite of sea walls built to reduce the energy
of the waves, coastal buildings would quickly be submerged
under several meters of water.
(soft suspenseful music)
These pool simulations are supplemented
by virtual simulations.
One developed by Professor Hiraishi's team
allows us to anticipate the progression
of a tsunami in Tokyo Bay.
Although it is five kilometers from the sea,
the area around the Olympic stadium could be hit
by a nine-meter high wave.
Simulations are carried out
to determine hazardous locations.
For example, a road will be hit by a wave very fast
so you should not take refuge there.
This building will have its entrance blocked
by the current of the tsunami so you should not go there.
(soft ominous music)
These models enable Kyoto University
to create an interactive evacuation plan.
In the event of an alert, a mobile phone application
shows the progression of the waves
and designates the nearest protected areas.
We've got messages coming in
on our cell phones, on the internet.
When you watch TV you have messages coming to you, too,
and they tell you where you have to run to be safe.
Fleeing and finding refuge is essential,
but limiting the impact of destruction is just as important.
(soft ominous music)
As the 2011 tsunami demonstrated,
port areas are among the most dangerous sites.
Ships can become giant projectiles.
For Professor Hashimoto of the University of Kobe,
evacuating them quickly in the event
of an alert is a priority.
Osaka Bay is very lively.
Every day and at any given moment
there are 30 to 50 boats sailing there.
We have no guarantee that in the event of a tsunami,
a situation they may have never experienced,
everyone would keep their cool
and that the ships would evacuate one after the other
in an orderly fashion.
That is why we're developing
an artificial intelligence system which will enable ships
to evacuate or maneuver automatically.
Despite technological advances,
Japan is living on borrowed time.
Like Osaka, a megalopolis of eight million inhabitants
and the country's second largest economic center,
a city built over time on embankments below sea level,
surrounded by hundreds of kilometers of protective walls.
What happened in 2011
was that the earthquake had weakened all the structures.
Part of the walls had fallen with the quake,
so when the tsunami came what we thought was effective
was no longer effective.
To date, even the most sophisticated
technologies can not predict earthquakes.
These artificial islands reclaimed from the sea,
built with houses, shopping centers,
and petrochemical industries
could be destroyed in an instant.
Faced with coming disaster, only education
and informed reactions of the population
will make it possible to save lives.
(soft ominous music)
We think we're taming nature, but nature dominates us.
Around the world, the science of tsunamis
is making great strides, but each new disaster
challenges the progress that has been made
to better protect us.
If we built power plants, hospitals, public buildings,
houses in areas that there's a high hazard,
we are adding layers and layers of vulnerability.
And with time, what we're finding around the world
is that our vulnerability from disasters
keeps increasing instead of diminishing.
The shoreline has always attracted humankind,
but its rapid urbanization creates more and more danger.
While ever more sophisticated technologies
allow us to be alerted as soon as possible,
learning to read nature with common sense
remains more vital than ever.
We say this worldwide.
If you are near the coast and you feel
any kind of ground shaking that lasts
more than 15 seconds, move away from the beach.
(suspenseful music)
