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Au cœur du désert californien se trouve une immense mer toxique qui n’aurait jamais dû exister. Pourtant, elle est aujourd’hui devenue l’une des catastrophes environnementales les plus alarmantes des États-Unis. Autrefois présentée comme une destination de villégiature florissante, la mer de Salton s’est transformée en un lac pollué qui rétrécit, libérant des poussières toxiques dans l’air et menaçant la santé des communautés voisines. Les scientifiques avertissent qu’à mesure que l’eau continue de disparaître, les sédiments du fond du lac exposés à l’air pourraient dégrader davantage la qualité de l’air et engendrer de graves problèmes environnementaux dans toute la région. Cette vidéo explore comment la mer de Salton a été créée par accident, pourquoi elle est devenue toxique et ce que font les experts pour éviter que la crise ne s’aggrave encore. Ce qui a commencé comme une erreur d’ingénierie est devenu une catastrophe grandissante, visible depuis l’espace.
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00:00In this moment, under the streets of Auckland, in California,
00:05two big rocks are blocked by one against the other.
00:11It seems nothing for a non-initiate,
00:13but the problem is that they can comprise a little more every year,
00:17accumulating energy like a ressort sous tension
00:19for more than 150 years.
00:22At about 9 mètres under the trottoir
00:24where people walk their children and take their café in the morning,
00:27a geological clock has already reached its end.
00:32And scientists now know, with an inquiet mind,
00:36what happens when it ends up leaving.
00:39Here's the story of Hayward's fall,
00:41one of the land land most dangerous in the United States,
00:46and extraordinary computer simulations
00:48which finally reveal what the next big disaster will do
00:52to millions of people.
00:55Let's start by the fall,
00:56because the fall of Hayward is not a geological geological
01:00lointain,
01:01hidden at the bottom of the wild nature.
01:04It is located on about 120 km
01:06in the middle of the east bay california,
01:10directly under the residential areas,
01:12schools, hospitals and motor routes
01:15in cities like Auckland and Berkeley.
01:17More than 2 millions of people live or work along their tracks,
01:21and according to the scientific consensus,
01:24she is in retard.
01:26The last big rupture of the fall of Hayward
01:29comes to 1868.
01:32This tsunami, estimated at a magnitude of 7,
01:35was devastating for the time.
01:38The
01:39buildings through Hayward
01:41and sent waves of shock to San Francisco.
01:44But here is what makes the current situation
01:47much more serious.
01:49The middle of the fall between two major disasters
01:52is of about 140 years.
01:55We are now at more than 150 years
01:58of this last rupture.
01:59The clock has not just reached its term,
02:02it has surpassed for more than 10 years.
02:06The numbers of the geological studies
02:09of the United States
02:09make it very concrete.
02:12It is about one chance
02:13on three,
02:14that a magnitude of magnitude 6,7
02:16or more
02:17hit this fall in the next 30 years.
02:21But the fall of Hayward
02:22does not act in an isolated way.
02:24When scientists
02:25take into account
02:26the fall connected to the region,
02:28such as the fall of Rogers Click
02:29in the north,
02:30the probability of a major rupture
02:32in the system
02:33reached 72%
02:35until 2043.
02:39This is not a distant hypothesis,
02:41it is a quasi-certainty
02:43of the most of us.
02:45So,
02:46what happens exactly
02:47when it falls?
02:49For decades,
02:51the answer was
02:51we are not really sure.
02:54There were general sismic models
02:55but the geology of the Baie
02:57of San Francisco
02:58is complex.
02:59A patchwork
03:00of hard rocks,
03:01of wood buildings,
03:02of deep rocks
03:03and of culinary formations
03:04and to predict
03:06how the seismic
03:07spread
03:07in this labyrinth
03:08surpassed the power
03:09of the available calculation.
03:11This has changed recently.
03:13The researchers
03:13of the Lawrence Livermore
03:14National Laboratory
03:15and of the Lawrence Berkeley
03:17National Laboratory
03:18have used
03:19some of the super-calculators
03:20the most powerful
03:21in the world
03:21to create 50 simulations
03:23distincts
03:24of a magnitude 7
03:25on the faille
03:26of Hayward.
03:27Each simulation
03:28was different
03:29the parameters.
03:30The exact point
03:30of the rupture,
03:32the way the glissement
03:33is spread
03:34on the surface of the faille,
03:35the speed of propagation
03:36of the fracture.
03:38The result
03:38is not a single prediction
03:39but a rich
03:40and detailed
03:41of possibilities
03:42showing not only
03:44where the secouss
03:44will be produced,
03:45but their intensity,
03:47their duration
03:47and why
03:48some areas
03:49face to risk
03:50much higher than others.
03:53Their discovery
03:54should change
03:55the way
03:55each resident
03:56of the bay
03:56sees its life.
03:59The main lesson
04:01of these simulations
04:01is the following.
04:02The soil
04:03does not fall
04:04uniform.
04:05The placement
04:06is a lot
04:07and the differences
04:08are not subtle.
04:10Take the islands
04:11of the East,
04:12such as Orinda
04:13and Moraga.
04:15These communities
04:16are based
04:17on the couches
04:17of sedimentary sedimentary
04:19and this geology
04:20acts
04:21as an amplificator.
04:23During a major
04:23disaster on the
04:24faille of Hayward,
04:25the secouss
04:26in these areas
04:27could be
04:28up to 50%
04:29more intense
04:30than in the west
04:30of the west
04:31located on the solid rocks.
04:33This is not a margin
04:34error,
04:35it is the difference
04:36between a building
04:36and a building
04:38that falls.
04:39And then,
04:40there is the valley
04:41of Livermore,
04:42confronted
04:42with a different
04:43problem,
04:44but also serious.
04:46The valley
04:47is in a geological
04:48basin
04:49and the ones
04:49seismic
04:50behave strangely
04:51inside the basin.
04:53They fall
04:54down,
04:54stuck between the
04:55walls,
04:56unable to escape.
04:59Instead of
05:00as usual,
05:01simulations show
05:02that the secouss
05:03could be prolonged
05:03for more
05:04two minutes
05:05at Livermore.
05:07Two minutes
05:07entire
05:08of violent secouss
05:09and supported.
05:10For the canalizations,
05:12the houses
05:12and the infrastructure
05:13industry,
05:14this duration is potentially
05:16catastrophic.
05:18In Auckland
05:19and Berkeley,
05:20directly on the line
05:21of failure,
05:22the main danger
05:22comes from what
05:23scientists call
05:24the impulsions
05:25of directivity.
05:26When the failure
05:28breaks,
05:28the fracture
05:29does not happen
05:30at one point.
05:31It falls along
05:32the failure
05:33and, by doing it,
05:34they project
05:34a concentrated energy
05:36like a wave
05:37emitted by a source
05:39in movement.
05:40The areas
05:40located directly
05:41in the trajectory
05:42of this wave
05:43receive violent
05:44and powerful impulses,
05:46particularly destructive
05:48for the high buildings.
05:50The sky
05:50and the tours
05:51of these cities
05:51are the most high risk
05:53with the acceleration
05:54of the ground
05:55to reach the equivalent
05:56of the gravity
05:58enough to submerge
06:00the structures
06:00who did not have
06:01been conceived
06:01for this specific threat.
06:06During this time,
06:07on the west west
06:08of the bay
06:08on the rock rock
06:10the situation
06:12is significantly different.
06:13The acceleration
06:14of the ground
06:15could be
06:1620% to 50%
06:17inferior
06:17to the most risk.
06:19San Francisco
06:21will certainly feel
06:22the storm,
06:23but the distance
06:24and the solid geology
06:25offer a significant
06:27protection.
06:28This does not mean
06:29that the west
06:30are sure.
06:31It means
06:32that they are
06:32more sure
06:33comparatively.
06:35To understand
06:36why geology
06:37creates such a marked
06:39difference
06:39it is useful
06:40to think
06:41at the way
06:41the seismic waves
06:43are really propagated.
06:44When a wave
06:45breaks,
06:46it sends waves
06:47in all directions,
06:48like a stone
06:49in a sand
06:50but contrary
06:51to the water
06:52the ground
06:52is not uniform.
06:54The rock
06:54hard
06:54transmits
06:55quickly
06:55and efficiently.
06:57The energy
06:58passes
06:58without delay.
07:00The sand
07:01of the sand
07:02of the sea
07:02will slow down
07:04the waves
07:05and force
07:06to amplify
07:06the same way
07:08that the ocean
07:08will be able to
07:10reach a few
07:11deep waters
07:12near the river.
07:13The sea
07:14of San Francisco
07:15depends on a
07:16extraordinary variety
07:17of materials,
07:18which explains
07:19precisely why
07:20two quarters
07:20separated from a few
07:21kilometers
07:22can experience
07:23the same
07:24of a radically different
07:26The simulations
07:28capture this
07:28complexity
07:29with a
07:30inequality
07:30and the results
07:32show clearly
07:32that geology
07:33is not a simple
07:34detail.
07:35It is the
07:36determining factor
07:37who decides
07:38who is
07:38and who is
07:39out of the sea.
07:40What makes these simulations
07:42really revolutionary,
07:43is that they do not produce
07:44simple abstract data,
07:46they produce
07:48exploitable information.
07:49The engineers
07:50can already use
07:51these results.
07:52For the sea of
07:54Oakland and Berkeley,
07:55the risk of
07:55impulse
07:56means that the buildings
07:57need to be specially
07:59conceived
07:59to absorb
08:00these
08:01bursts and suddenly
08:02rather than the
08:03angular movement
08:04more lent
08:04of the farthest
08:06At Livermore,
08:08the foundations
08:08of the new constructions
08:09must take into account
08:10of the prolonged duration
08:11and not only
08:13of the maximum intensity
08:15In the islands
08:16the stability
08:17of the walls
08:17becomes a major concern
08:19The houses
08:20to the coast
08:20make face
08:21a huge risk
08:22of sinking
08:23of the terrain
08:23when the
08:24secouss are amplifying.
08:25For the public infrastructure,
08:27the Bay Area Rapid Transit
08:28, the BART
08:29and the motorway network
08:31of the region
08:31are now prioritized
08:33for the
08:33use of the norm
08:34on the basis
08:35of the directives
08:36and simulations
08:37produced.
08:38The faille
08:39is not only
08:39the buildings,
08:40it is only
08:41the transport networks
08:42that people need
08:43desperately
08:43after a major event.
08:45And for ordinary inhabitants,
08:47the implications
08:48are personal and concrete.
08:50Fixer the heavy buildings,
08:51the heating,
08:52and the bibliothèques
08:53reduce the risk
08:54of illness.
08:55The applications
08:55of precoces
08:57can give a few seconds
08:58of warning
08:58before the arrival
08:59of the secouss.
09:00enough for
09:01to increase,
09:02to protect
09:02and to grip.
09:03The emergency room
09:05for at least three days
09:06are not excessive preparation.
09:08For a region
09:09so exposed,
09:10it is simply
09:11good sense.
09:12The science
09:13of the seismic prediction
09:15avance quickly.
09:16These simulations
09:17are already
09:17extended to the faille
09:18of Saint-Landréas,
09:19modeling
09:20potential events
09:21of magnitude 7,5
09:23or more.
09:25The cartography
09:26souterraines
09:27at a higher resolution
09:28will allow
09:28to still affine
09:29the models.
09:30But the simulation
09:31of the faille
09:32of Hayward
09:32tells us something
09:33deep.
09:35We don't have to be
09:36impuished
09:36against this threat.
09:38The sol
09:39under the bay
09:39of San Francisco
09:40is not a mystery.
09:41We know
09:42where the danger
09:42is concerned.
09:44We know
09:45why some cities
09:46will fall stronger,
09:47why some valleys
09:48will fall longer,
09:49and why some buildings
09:51face to risks
09:52that others do not.
09:53The question
09:54is not to know
09:54if this disaster will happen.
09:56The question
09:57is to know
09:57if we will be ready
09:58when it will fall.
10:01Since 2000,
10:03the world
10:03has been struck
10:03by more than 1700
10:04lands of the earth
10:05of a magnitude
10:06above 5.
10:07Many of them
10:08were produced
10:09around the fog
10:10located on the Pacific Ocean.
10:12in the Pacific Ocean.
10:13In the North,
10:14the biggest threat
10:15is the faille
10:16of San Andreas,
10:17susceptible
10:18to cause
10:18a earthquake
10:19of a magnitude
10:20inégalée,
10:21which is called
10:23Big One.
10:23The potential destruction
10:25of the California
10:25is a terrifying perspective
10:27which could have
10:28consequences
10:29inimaginable.
10:30But the Big One
10:31is only the beginning
10:32of what we expect.
10:35The scientists
10:37have predicted
10:38an event
10:39in 2030.
10:41The probability
10:42that we will assist
10:43to this immense
10:44tsunami
10:44of the Big One
10:45is of 70%
10:47and its magnitude
10:48should reach
10:49the 6,7%
10:50on the scale
10:51of Richter.
10:52It will have well
10:52to origin
10:53the faille
10:53of San Andreas.
10:54But our predictions
10:55are unfortunately
10:56insufficient
10:57for the moment.
10:58However,
10:59a big earthquake
10:59of a big earthquake
11:00of a large amount
11:00that gives us
11:02the time to prepare
11:04the catastrophe.
11:05If we were able
11:06to travel in the time,
11:07we would be able
11:08to see
11:09the earthquake
11:10of the earthquake
11:11which has ravaged
11:11San Francisco
11:12and the fort
11:13Tejan.
11:13The buildings
11:14built
11:14in a long time
11:15are not at the peak
11:16of this kind of
11:17tsunami.
11:18Even if they
11:21hold the coup,
11:22it must not be
11:22penetrated.
11:23But the buildings
11:24are not the most dangerous.
11:26You have to pay attention
11:27to the electricity
11:28and the gas engines
11:29and the gas engines.
11:30Your house
11:31on the hill
11:31is perhaps charmante,
11:33but it is
11:34dangerously exposed.
11:35Lors
11:36of the earth,
11:37a cliff
11:37can cause
11:38a huge cliff
11:40which will destroy
11:40everything on its own.
11:42Say goodbye
11:43to travel
11:43because all the routes
11:45will be destroyed.
11:46Prepare
11:46reserves
11:47of water
11:47and food
11:48because you will not
11:49be able to go.
11:50This catastrophe
11:51will not be good
11:52to go.
11:52The United States
11:53will have to pay
11:54about 200 billion dollars
11:56to get out of the disaster.
11:57You know
11:58at least,
11:59the earthquake
11:59will not cause
12:00a tsunami.
12:01But there is something
12:02that can cause
12:03even more damage
12:04than this big one.
12:06The famous
12:06zone of subduction
12:07of Cascadia
12:08begins in California
12:09and ends up in Vancouver
12:11in Canada.
12:12The peak
12:12of San Andreas
12:13is nothing compared
12:14to this zone.
12:15It could
12:16cause the total
12:17of the hill.
12:18A terrifying vision.
12:20The subduction
12:21is a phenomenon
12:22of an explosion
12:22of a tectonic
12:24under another
12:24of a lower density
12:25of a lower density.
12:26We have here
12:27the North American
12:28and the Juan de Fuca.
12:30The areas of this type
12:32are generally
12:32to avoid
12:33because the risks
12:33of a tsunami
12:34are very high
12:35and they are
12:36extremely dangerous
12:38especially because
12:39of the sea.
12:41a risk
12:42we who are
12:43at earth.
12:43Yes,
12:44because the tsunami
12:45giants can occur
12:46inunding the cities
12:48and destroying
12:48the coast.
12:49At the moment
12:50the most active zone
12:52is the fire
12:52zone.
12:53The Cascadia zone
12:54is perhaps less active
12:55but it is
12:56like a sleeping beast.
12:58It could
12:59wake up
12:59and destroy
13:00everything that is
13:01on its path
13:01causing damage
13:03without precedence.
13:04The last time
13:05that such a tension
13:06was released
13:06was in the 1700s.
13:09Unlike the
13:10of San Andreas
13:11this one
13:12will cause
13:12massive tsunamis
13:13and these
13:14will be more violent.
13:15We hope
13:16that you will
13:17camp in a field
13:17at this time
13:18because most of the buildings
13:19and the ponts
13:20will probably be
13:21destroyed.
13:22Prepare you also
13:23to the replicas
13:23which will be
13:24devastating.
13:25The nature
13:26will not be
13:26flooded.
13:27The lands
13:28will change
13:29and our houses
13:31will be
13:32unknown.
13:33Fortunately,
13:34there is a light
13:34at the end
13:35of the tunnel
13:35and scientists
13:36do everything
13:37to ensure
13:38our security.
13:40The new rules
13:40are made
13:41in order.
13:42Each new building
13:42must be able
13:43to resist
13:44massive shocks.
13:45They develop
13:46modern alert systems
13:48and every new infrastructure
13:49must follow
13:50strict rules
13:51in terms of
13:52resistance
13:53to the earthquake.
13:54The plaques
13:55Ruan de Fuca
13:56and North American
13:56are currently
13:57blocked
13:58but they will not
14:00remain eternally.
14:01When they will
14:02end up,
14:03prepare you
14:04to a strong
14:04rescue.
14:05Plus
14:05you are close
14:06to the epicenter,
14:07the damage will be important.
14:09But even
14:10if you have the chance
14:10to be close
14:11to the epicenter,
14:12it may be possible
14:13that you feel
14:13the sol
14:14tremble
14:14during a certain time.
14:16If we compare
14:16the area
14:17of Cascadia
14:18and San Andreas
14:20we see
14:21that the area
14:22of Cascadia
14:23is much more dangerous.
14:24In 1994,
14:27an enormous
14:28tremblement
14:28of land
14:28of magnitude
14:296,7
14:30was produced
14:31in Northridge
14:32close to the
14:33fall of San Andreas.
14:35Unfortunately,
14:36many people
14:36have not survived
14:37and there were
14:38many deaths
14:39at the time
14:40the buildings
14:41were not enough
14:42to resist
14:43the tremblements
14:44of land
14:44and many of them
14:46have been
14:46damaged.
14:47The area
14:48of Cascadia
14:49could potentially
14:50cause a tremblement
14:51of land
14:51of magnitude 9.
14:52A tsunami
14:53of magnitude 6
14:54has a power
14:55equivalent to
14:56approximately 20 million
14:57kilograms of dynamite.
14:59But the power
15:00of mind
15:00is equivalent
15:02to 20 million
15:03of kg
15:04of this same dynamite.
15:05The倒
15:06land
15:06of land
15:07was
15:07almost
15:07to go
15:07not registered, it was produced in Chile.
15:10His magnitude was of 9,5 and he almost destroyed everything.
15:14Suppose you have survived the earth tremblement.
15:17Your ennuis are far away.
15:19Later, a mass tsunami hit the coast with waves
15:23reaching up to 30 meters in certain areas.
15:27This is not the case of the earth tremblement
15:28of San Andreas, which can not produce big waves.
15:32You can say goodbye to your beautiful garden,
15:34because it will destroy the trees and plants
15:37and change the environment for a lot of time.
15:40The only positive point is that you will not need
15:42decoration for Halloween,
15:44because all these trees will look like a phantom.
15:47The waves, the secousses and the spread of the zone
15:50will make this natural disaster even more redoutable
15:54than the cause of San Andreas and the Big One.
15:57A tremblement of the earth is similar to this produce
16:00there about 300 years.
16:01Many others have been recorded
16:03over the last 3500 years,
16:06which proves that they continue to produce
16:09every four to 600 years.
16:10Technically,
16:11it remains between 100 and 300 years
16:13before the next event.
16:15We don't always know how exactly
16:17how exactly works the zone of subduction
16:19of Cascadia,
16:19because we have discovered it
16:21in 1970.
16:23This zone is very frightening,
16:25it is one of the most dangerous
16:26of the planet.
16:27It has been discovered by chance
16:29by researchers
16:30who studied the fire fire.
16:32They wanted to know
16:33if there were problems
16:34in this zone
16:35over the last few years
16:36and the proof
16:37was found in their feet.
16:38In the state of Washington,
16:40there is a sinister forest
16:41where nothing will move
16:42for years.
16:43When researchers
16:44analyzed the soil,
16:46they found a huge amount of salt.
16:48They made the approach
16:49and concluded
16:50that a massive tsunami
16:51was the origin of this situation.
16:53The experts
16:54do not always know
16:55exactly when the forest
16:56was destroyed.
16:58Fortunately,
16:59Japan has kept
16:59the traces
17:00of a gigantic
17:01tremblement of earth
17:02which had a similar effect.
17:04It is the one
17:05that was produced
17:06in the year 1700.
17:07There is a chance
17:08on three
17:09that the next one
17:09will be produced
17:10in 2050.
17:11You must know
17:12how to act in case
17:13of a tremblement of earth
17:14so listen carefully.
17:17The inhabitants
17:18of the region
17:19that we are talking
17:19have no experience
17:21of this type.
17:22It is relatively easy
17:24to survive
17:25to this kind of catastrophe.
17:27It is the tsunami
17:28that will follow
17:28which constitutes
17:29the real danger.
17:31After the initial secouss
17:31find the highest terrain
17:34of your region
17:34and leave you there.
17:36No matter
17:36only the essentials
17:37like food
17:38and water
17:39leave your collection
17:40of baseball cards
17:41at you.
17:42After the first wave
17:43don't go back
17:44immediately.
17:45The seismologists
17:46say that
17:46very likely
17:47there will be others
17:48and they have proved it.
17:50The 22 May 1960
17:52the seismologist
17:54Jerry Estone
17:55and his four friends
17:56went to Hawaii
17:57to observe
17:58a tsunami
17:59that was going to happen
18:00until midnight.
18:01They installed their material
18:02on the bridge
18:03of Wailuku
18:03and planned an
18:04itinerary of rescue.
18:06This bridge
18:06was destroyed
18:07during the previous tsunami
18:08but the new bridge
18:09was much higher
18:11and better adapted.
18:12After midnight
18:12the water
18:13was found
18:14at 1,2 m
18:15above its level
18:16the second wave
18:17hit 1,5 m
18:19after midnight
18:19and the water
18:20is still up
18:202,75 m
18:22at 1 h
18:23in the morning.
18:24The water
18:24is then redesigned
18:25about 2 m
18:26but the horror
18:27was not finished.
18:29They have then seen
18:30a wave of a little
18:31more than 6 m
18:31above.
18:32This proves
18:33that the tsunamis
18:34are unprecedented
18:35and that we must
18:35absolutely listen
18:36to the experts
18:37to stay safe.