• 2 weeks ago
Vers la fin de 2004, l'un des désastres les plus dévastateurs de l'histoire moderne s'est produit - un immense séisme sous l'océan Indien a déclenché un tsunami qui a remodelé des côtes entières. 🌊 Le tremblement de terre, avec une magnitude impressionnante de 9,1-9,3, fut l'un des plus puissants jamais enregistrés, et le tsunami qu'il a déclenché a causé des destructions dans 14 pays, de l'Indonésie à la Somalie. Plus de 230 000 vies ont été perdues et des millions de personnes ont été déplacées, laissant le monde sous le choc devant l'ampleur de ce désastre. Les scientifiques disent que cela est arrivé en raison du violent déplacement des plaques tectoniques, et ce qui fait peur, c'est que de tels événements peuvent se reproduire. Mais la tragédie a aussi uni le monde, les pays se hâtant de fournir de l'aide et de reconstruire ce qui avait été perdu. Bien que nous ne puissions pas arrêter les tremblements de terre ou les tsunamis, de meilleurs systèmes d'alerte et une meilleure préparation pourraient sauver d'innombrables vies à l'avenir. 🌏 Animation créée par Sympa.
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Transcript
00:00It is 7h59 when a man, abruptly pulled out of his sleep,
00:05finds himself confronted with a mysterious and irresistible force.
00:10While he tries to understand what is happening,
00:12a gigantic column of water, 30 meters high,
00:15is already rushing towards his hometown.
00:18In less than 20 minutes,
00:19a huge devastating wave will take buildings, trees and vehicles,
00:24costing the lives of most of his loved ones and friends.
00:28This scenario can, alas, happen at any time.
00:31On December 26, 2004,
00:34thousands of tourists from Europe and America
00:37savored the pleasures of the tropical beaches of Thailand,
00:40Sri Lanka and Indonesia,
00:43when an underwater earthquake of an exceptional magnitude
00:46of 9.3 struck off the west coast of Sumatra.
00:50This earthquake, the most powerful ever recorded in Asia,
00:54triggers one of the most destructive tsunamis in history,
00:58known as the Christmas Day Tsunami.
01:01In a few hours, only 230,000 lives will be lost.
01:04The city of Bandahaset, located on the island of Sumatra in Indonesia,
01:08and populated by 260,000 inhabitants,
01:10is located closest to the epicenter.
01:12Less than 30 minutes after the earthquake,
01:14huge waves, reaching the height of a 10-story building,
01:18hit the city.
01:19More than 60,000 people die on the field,
01:22and the destruction is so catastrophic
01:24that almost no one survives in the trajectory of the waves.
01:28Then, the tsunami hit Thailand.
01:31The waves, crossing the Indian Ocean at a speed of 800 km per hour,
01:36reach the coasts of Phang Nga and Phuket
01:38about 90 minutes after the earthquake.
01:41Despite this considerable time lapse,
01:43neither the inhabitants nor the tourists are prepared.
01:46Many are those who, intrigued by the unusual receding of the sea,
01:50go to the beach to observe the phenomenon
01:52before being submerged by a water wall.
01:55That day, nearly 5,400 people,
01:58including 2,000 foreign tourists,
02:00will lose their lives in Thailand.
02:01An hour after hitting Thailand,
02:04the tsunami hit southeast India, near Chennai.
02:07Waves loaded with debris sink several kilometers into the land,
02:11taking more than 10,000 lives.
02:13In Sri Lanka, the situation is even more dramatic.
02:16More than 30,000 people succumb,
02:18while hundreds of thousands others find themselves homeless.
02:22The exceptional power of the tsunami
02:25even manifests itself at a considerable distance.
02:28Eight hours after the earthquake,
02:30it makes its last victims in South Africa,
02:338,000 kilometers from the epicenter.
02:35There, unpredictable waves take the swimmers by surprise.
02:40The workers of the National Tsunami Alert Center
02:43attribute the magnitude of this destruction
02:45to the extraordinary power of the earthquake.
02:47It is the result of a subduction fault
02:50where dense oceanic plates slide
02:52under lighter continental plates.
02:55These faults, among the largest in the world,
02:57are located under the oceans.
03:00The 2004 earthquake
03:02fractured an area of 1,500 kilometers
03:05between the Indian and Australian plates,
03:07at a depth of 50 kilometers under the seabed.
03:10In addition, instead of limiting itself to a brief shake,
03:13the earthquake lasted 10 minutes,
03:15releasing a colossal energy.
03:17During this period of time,
03:18huge portions of the ocean floor rose 40 meters,
03:22a movement of a prodigious magnitude.
03:24This sudden movement generated gigantic waves
03:27that spread across the ocean,
03:29similar to the circles formed by a galley launched into the water.
03:33However, the tsunami waves
03:35are nothing like those of the surfers.
03:38These waves look more like a tumultuous river,
03:42submerging everything in its path.
03:44Being caught in these waves
03:46almost makes any chance of survival illusory.
03:49If the currents don't drag you under the surface,
03:51the debris carried by the waves will.
03:54This explains why, during earthquakes,
03:56there are many injured and the human losses are relatively small.
04:00On the contrary,
04:02tsunamis cause much more deaths than injuries,
04:04because surviving such a disaster is extremely difficult.
04:08Devastating tsunamis like the one in 2004 are rare,
04:12which explains why India and Sri Lanka
04:14did not have similar precedents.
04:17This lack of experience,
04:18associated with the absence of warning systems,
04:21has made the consequences even more dramatic.
04:23The populations, far from the epicenter,
04:26did not feel the earthquake.
04:27Deprived of warning signs,
04:29official warnings or historical memories,
04:32they were taken for granted
04:34when the waves ravaged these densely populated coastal areas.
04:37The Pacific Ocean, the largest in the world,
04:40is the main theater of earthquakes and tsunamis.
04:43Locally destructive tidal waves
04:45hit this region every 1 to 2 years.
04:48Indeed, 76% of the recorded tsunamis
04:52occurred here.
04:53In addition,
04:5499% of the victims of tsunamis
04:57are linked to local or regional events,
05:00which occur more frequently
05:02and hit coastal areas
05:04with formidable speed.
05:06One question remains, however,
05:08could a tsunami as devastating as the one on December 26
05:11occur again?
05:13The answer is unfortunately complex.
05:15A warning system was put in place in the Indian Ocean
05:18to warn coastal nations of potential tsunamis.
05:22However,
05:23human behavior remains a major obstacle.
05:25This was illustrated in a magnitude-of-nature test in 2012,
05:29when many inhabitants of Banda Ase,
05:32in Indonesia,
05:33ignored the evacuation towers despite a tsunami warning.
05:36It seems that the experiment is not always enough
05:39to anchor the right reactions.
05:40The Indian Ocean warning system
05:43is based on underwater pressure sensors
05:45located near tectonic faults.
05:47These sensors record variations
05:49and transmit data to surface buoys,
05:52which then relay this information by satellite
05:55to ground control centers.
05:58Authorities analyze the data
06:00and decide whether alerts should be issued
06:02or whether evacuation must be pronounced.
06:05Ase,
06:06located on one of the most active faults in the world,
06:09has adopted additional security measures.
06:12Sirens have been installed in coastal cities,
06:15inhabitants receive alerts on their phones,
06:18and reinforced concrete evacuation towers,
06:20capable of sheltering 500 people,
06:23serve as a specially designed security zone
06:25for emergency situations.
06:27To assess the preparation of the populations,
06:30authorities organized an evacuation exercise in 2009.
06:3418 countries in the Indian Ocean
06:36participated in this simulation of a powerful earthquake,
06:39mobilizing thousands of coastal communities,
06:41and the officials concluded to the success of this exercise.
06:44The first real test of the system took place in April 2012,
06:49when a magnitude 8.6 underwater earthquake
06:52to the west of Ase triggered tsunami alerts.
06:55Although no significant wave was formed,
06:58this event highlighted major shortcomings.
07:01Many inhabitants ignored the evacuation towers
07:03and chose to flee by car or motorcycle,
07:06causing huge traffic jams in the city.
07:08This left some people stuck in areas at high risk in the event of a tsunami.
07:13The situation was chaotic,
07:14to the point that some even decided to return to the beach
07:18in search of signs of a tsunami.
07:20A very serious mistake.
07:22There is still a lot to be done
07:24to improve the chances of survival in the event of a tsunami.
07:27What is essential, however,
07:29is to recognize the signs of a tsunami.
07:31This starts with violent earthquakes.
07:34Powerful earthquakes in coastal areas can trigger tsunamis.
07:39If you notice that the water on the beach is retreating at a disturbing speed,
07:43exposing the seabed, reefs and fish,
07:46leave immediately.
07:48Unusual sounds from the ocean can also be a warning.
07:53A loud and roaring noise,
07:55comparable to that of a train or a jet engine,
07:58can also signal the arrival of a tsunami.
08:01If you notice one of these signs,
08:03it is crucial not to wait for the official evacuation orders.
08:07Leave the lower areas immediately
08:09and head for higher ground.
08:12If you are at home,
08:13make sure that all members of your family are informed of the situation
08:17and follow the instructions of the authorities.
08:19Also keep in mind that local-origin tsunamis can strike in a few minutes,
08:24which requires a quick reaction.
08:26For a more distant tsunami,
08:28it is possible to have more time to evacuate.
08:31If you can't get far enough,
08:33find shelter in high concrete buildings.
08:37Avoid small buildings or dwellings located in low areas,
08:41where the risks are increased.
08:43If you are at sea, stay offshore,
08:45because tsunamis are less dangerous in deep water.
08:48It is therefore essential to avoid returning to the port
08:51when a tsunami alert is in effect.
08:53If you are already at the port,
08:55consult the port authorities to obtain instructions.
08:58And if you have the opportunity to head for deep waters,
09:02do so calmly.
09:03For small boat owners,
09:05it may be preferable to leave the boat and look for high-rise shelters.
09:09And, above all,
09:11prioritize your safety by gaining a higher ground rather than saving your property.
09:16For inhabitants of coastal areas,
09:17some precautions can be taken in advance to protect your property.
09:21Since the majority of tsunami waves are less than 3 meters high,
09:25you could consider raising your house to limit the damage.
09:29You can also consult an engineer to assess its strength
09:33and reinforce it if necessary.
09:36Finally, do not forget to secure the dependencies
09:39and install fences that will allow animals to take shelter in high places.

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