Flood. Tsunami is a catastrophic natural phenomenon

A giant wave never appears just like that, the main thing is to be aware of the dangerous regions and take precautions.

Causes of a tsunami

• Tsunamis are caused by earthquakes, but not every earthquake will necessarily cause a tsunami.
• The great Lisbon earthquake of 1755, which claimed the lives of more than 50 thousand people off the coast of Spain and Portugal, is associated by experts with the tidal effects of the Moon and the Sun on the earth's crust.
• The 1998 tsunami, which demolished everything in its path in the Papua New Guinea region, arose due to a landslide, the descent of which, in turn, provoked an earthquake of medium power ().
• The so-called "meteorological" tsunamis appear against the background of typhoons: after a sharp turn of the typhoon to the side, the resulting wave can continue to move independently (for example, the 2011 tsunami near the English city of Plymouth was caused by a storm in the Bay of Biscay).
• "Exclusive" tsunamis are caused by underwater volcanic eruptions (for example, the tsunami of 1883, formed after the eruption of the Krakatoa volcano), meteorite falls (the documentary of the National Geographic channel mentions traces of a tsunami that remained in Texas after a meteorite fall 65 million years ago ) and man-made disasters.

Philippines, Malay Archipelago

The Philippine Islands are located in a seismically active zone. And where there are earthquakes, there are tsunamis, and which of the seven thousand islands will be under attack in current year, is impossible to predict. In 2013, these were the islands of Samar and Leyte, where waves up to 5 meters high claimed the lives of 10 thousand people and left about half a million local residents homeless. And the worst tsunami in the history of the Philippines occurred in 1976, when, as a result of an earthquake in the Cotabato Ocean Trench, a wave hit the island of Mindanao, killing 8,000 people.

Gizo, Solomon Islands

The Solomon Islands, tiny patches of land scattered across the Pacific Ocean, are defenseless against the destructive power of the tsunami, which was confirmed in 2007, when the cities of Gizo and Noro completely disappeared under water.

Honshu, Japan

In 2012, a 7.9 magnitude earthquake that occurred near the Philippine city of Guan “rolled back” in Japan with a tsunami a little over half a meter high, covering the metropolitan area and Fukushima Prefecture. Compared to the truly horrendous devastation of 2011, when a magnitude 9 earthquake dubbed the "Great East Japan Earthquake" was followed by a tsunami up to 40 meters high, flooding a total area of ​​561 square kilometers.

Miyagi Prefecture (327 km 2) was hit the hardest, and the highest wave height (40.5 meters) was recorded in Iwate Prefecture. Considering that the word “tsunami” itself came to us from the Japanese language (literally translated as “big wave in the harbor”), the Japanese, who had been familiar with this natural phenomenon for centuries, were not ready for a tragedy of such magnitude.

Maldives

Despite its seemingly vulnerable position, the Maldives archipelago experienced the only major tsunami in 2004. There is a threat, but coral reefs serve as a reliable natural system for protecting the island from surprises from the ocean.

More dangerous than the waves

• The mechanism of formation of a tsunami differs from the mechanism of formation of an ordinary wave, and this is where its danger lies.
• At strong wind the height of an ordinary wave can significantly exceed the height of an average 5-meter tsunami and even reach a 20-meter mark, but the length of such a wave is not more than a couple of hundred meters.
• During underwater earthquakes, the entire water column comes into motion, so that the length of a tsunami wave is measured in thousands of kilometers, and the speed can reach 1000 km / h.
• An ordinary wave is driven by the wind, and a tsunami carries a huge charge of energy, moving towards land with all its might.
• While the storm wave in narrow spaces loses its pressure, the power of the tsunami, on the contrary, is concentrated there, and it destroys everything in its path.

Phuket, Thailand

A magnitude 9 earthquake brought death and destruction to the Thai island of Phuket in 2004. Despite the fact that the epicenter of the earthquake was in the Indian Ocean near the island of Sumatra, the tsunami that followed it reached the shores of Indonesia, Thailand, Sri Lanka, India and even South Africa. Three waves hit in turn, numerous buildings, local residents and tourists were under water.

Hilo, Hawaii

In the Hawaiian Islands, more precisely, in the city, the International Tsunami Warning Service is located. The place was not chosen by chance: Hawaii is regularly covered by waves about 2 meters high, while the main blow falls on the city of Hilo, which is located on the shores of the bay of the same name. Despite the small wave height, Hawaiian tsunamis are among the most dangerous, because if a person falls into a tsunami wave on one of the local sandy bays with a very short beach, he will simply be smashed against the rocks. But if you are careful, then there is nothing to worry about: all such areas are marked with warning signs, and sirens are installed along the banks of the islands.

Alaska, USA

Alaska had two powerful tsunamis in a row at once: in 1957 and 1958, giant waves covered the Andreanov Islands and Lituya Bay, respectively. In 1958, the impact of the wave was so strong that the whole strip of land was actually destroyed - the La Gaussy spit.

Kamchatka, Russia

Tsunami waves come to Kamchatka from a zone prone to earthquakes, which is located in the Kuril-Kamchatka and Aleutian trenches. The three most powerful attacks of ocean waters occurred in the last century: in 1923, the wave height reached 30 meters, in 1952 - 15 meters, in 1960 - 7 meters.

Iquique, Chile

On May 22, 1960, an earthquake of magnitude 9.5 occurred near the Chilean city of Valdivia, the strongest earthquake in modern history humanity. And of course, there was a tsunami: in addition to the damage caused directly to the Chilean coast by a 20-meter wave, it reached Alaska, the shores of the Kuril Islands, Japan and swept the Hawaiian city of Hilo, taking about 6 thousand people into the ocean. In 2014, residents of the port town of Iquique were evacuated, where, after an earthquake of 8.2 points, a two-meter tsunami wave came.

Acapulco, Mexico

Despite the fact that the April 2014 earthquake of 7.2 magnitude did not cause a tsunami, the Mexican resorts of Acapulco and Zihuatanejo are under constant threat of a sudden onset of a killer wave. So if the ocean suddenly retreated from the shore, it's time to run.

Tsunami statistics

What to do if "covered"

• If you are in the coastal zone and feel an earthquake, leave the coast within 15-20 minutes.
• If you didn't feel an earthquake, you can guess the approach of a tsunami by a strong ebb tide.
• While the tsunami is approaching, in no case do not waste time in vain: do not go down to look at the exposed seabed, do not shoot the wave with your camera. Immediately look for a hill at least 40 meters in height, preferably warning others about the danger without sowing panic.
• If you are in a building (for example, a hotel) and there is no time left to look for a hill, go up to the upper floors of the building and barricade the windows and doors. Borrow safe place: there should be no potentially dangerous objects near you (for example, cabinets that can fall or mirrors that can break).
• If you can't find a hill, try to take cover behind any significant water obstacle (for example, a strong tall tree or a large stone) and cling to it so that you are not carried away by the flow of water into the ocean.
• If a tsunami caught you on the high seas (for example, you were on a ship and you were thrown into the water by a wave), do not panic, take a breath, group yourself and cover your head with your hands. Having surfaced, get rid of wet clothes as quickly as possible and find any object that you can cling to (in 2004 in Thailand, one of the survivors managed to swim out, clinging to the tail of a crocodile, and the other to a python).
• After the elements have raged, do not return to the sea for 2-3 hours: a tsunami is a series of waves.

Photo: thinkstockphotos.com, flickr.com

A tsunami is a series of destructive and very dangerous waves resulting from seismic activity or other similar underwater events. Behind last years The tsunami caused an incredible amount of damage. To survive a tsunami, you must be prepared, alert and calm. This article outlines the steps you need to know and follow to help you survive a tsunami in the future.

Steps

Part 1

Be aware of potential hazards in advance. It is important to know in advance if there is a risk of a tsunami where you live. You are probably in danger if:

• Your home, school or place of work is located in a coastal area.
• Your home, school or place of work is located on a flat or slightly hilly area, and the altitude is close to zero. If you don't know how high above sea level your home, school, and workplace is, find out. Some local authorities use altitude as the hazard level.
• There are warning signs indicating that the area is prone to tsunamis.
• Local authorities have published information about the potential threat of a tsunami.
• The natural boundaries of the sea, such as embankments and dunes, were leveled to develop the area.

1. Find out if tsunamis have hit your coastal region in the past. Go to the library or send a request to the local administration. FEMA (Federal Emergency Management Agency) has a website where you can learn online about flood hazards.

   Collect essential supplies in an easily accessible place. In the event of a tsunami (or other natural disaster) approaching, you will most likely need a few items to survive, and quickly. It is extremely useful to gather essentials and a survival kit in advance:

   • Gather your essentials. Food, water, and a first aid kit are the bare minimum. Leave the kit in a prominent, easily accessible place known to all household members. In addition, next to a set of essentials, it does not hurt to leave a raincoat or other raincoat for each person.
   • Assemble your personal survival kit for each family member, as well as a common set with shared items. Include necessary medicines for each family member. Don't forget the vital things for your pets.

2. Develop an evacuation plan. To be of any use, an evacuation plan must be prepared in advance. When designing it, you should consider your family, place of work, school, and the wider community. If necessary, start developing a mass evacuation plan if your county does not have one. Take the lead in developing such a plan, and involve local authorities and other residents. The lack of an evacuation plan and warning systems puts you, your family, and your entire community at increased risk of injury and death during and after a tsunami. Some mandatory items that must be present in every evacuation plan:

   Pay close attention to government warnings. If the local authorities have taken the time to report the danger, you should listen. Find out how they will warn the public about the danger so that you do not make a mistake and do not ignore the warnings voiced. Share this information with your family, friends, neighbors and others. If the local government publishes pamphlets, has launched a website, or uses another source of information, volunteer to distribute copies of the pamphlets or ask the local government to do so.

Part 3

Drop all belongings. In the event of a tsunami, save lives, not things. Attempts to collect belongings at the cost of precious time may interfere with your rescue. Grab a set of essentials, warm clothes, family and leave immediately. Tsunami survivors acted quickly and generally did not try to salvage property.

Move deep into the mainland and rise to higher ground. The first thing you should do is move away from the coast, lagoons and other bodies of water towards higher ground, and even hills or mountains. Don't stop until you're 3.2 kilometers inland or 30 meters above sea level.

Climb high. If you're trapped and can't get off the shore, climb up. This, of course, is not The best decision, since the building may collapse, but if you have no other choice, choose a tall, strong, reliable building and climb it. Climb as high as you can, even on the roof.

Climb a strong tree. As a last resort, if you're trapped and can't go deep into the continent or climb a tall building, find a strong, tall tree and try to climb it as high as you can. There is a danger of a tsunami knocking down a tree, so use this shelter only if no other options are available. The more powerful the tree, the higher you can climb it, the more comfortable it will be to rest on its branches (you can sit on the tree for many hours) and the more chances you will have to survive.

Such a phenomenon as a tsunami is as old and indomitable as the ocean. Eyewitness accounts of the terrible waves, passed from mouth to mouth, became legends over time, and written evidence began to appear about 2,000–2,500 years ago. Among the probable reasons for the disappearance of Atlantis, which occurred about 10,000 years ago, some of the researchers also name giant waves.

The word "tsunami" came to us from the Land of the Rising Sun. It is Japan that is most affected by the tsunami on the planet. She felt the grim consequences of the tsunami, which took many thousands of lives and caused enormous material damage. In the Pacific Ocean, tsunamis occur most often. In Russia, the Far Eastern coasts - Kamchatka, the Kuril and Commander Islands and, partially, Sakhalin, are subject to regular attacks by giant waves.

What is a tsunami? A tsunami is a giant wave that captures a huge amount of water, lifting it to a great height. Such waves are found in the oceans and seas.

The emergence of a tsunami

What can make plain water transform into such a destructive phenomenon of nature, endowed with a truly infernal power?

Tsunamis are long and high waves generated as a result of a powerful impact on the entire water column in the ocean or other body of water.

A common cause of catastrophic tsunamis is the activity that occurs in the bowels of the Earth. For the most part, water monsters are provoked by underwater earthquakes, because the study of this destructive phenomenon became possible only after the science of seismology appeared. A direct relationship between the strength of the wave and the strength of the earthquake was recorded. This is also affected by the depth at which the push occurred. Thus, only waves generated by earthquakes of high energy, with a magnitude equal to or greater than 8.0, have significant destructive power.

Observations show that tsunamis occur when a section of the surface of the sea or ocean suddenly shifts in the vertical direction after the corresponding section of the seabed has also shifted. Experts understand tsunamis to be the so-called long-period (that is, going far from each other) marine gravity waves that suddenly arise in the seas and oceans precisely as a result of earthquakes, the sources of which are located under the bottom.

The ocean floor trembles with colossal energy and gives huge faults and cracks, which lead to subsidence or elevation of large areas of the bottom. Like a giant underwater ridge rushes the entire volume of water from the bottom to the very surface, in all directions from the hearth. Ocean water near the surface may not absorb this energy at all, and ships passing through them may simply not notice a serious disturbance of the waves. And at depth, the future catastrophe begins to gain momentum and rushes at breakneck speed to the nearest shores.

Tsunamis arise from explosions of underwater volcanoes, and as a result of bottom collapses. Coastal landslides, caused by the fall of a huge mass of rock into the water, can also be the cause of a tsunami. Tsunamis with deep-seated foci usually have great destructive power. In addition, the causes of tsunamis are surges of water into bays caused by typhoons, storms and strong tides, which, apparently, can explain the origin of the Japanese word "tsunami", which translates as "big wave in the harbor."

Giant waves have great speed and tremendous energy, and therefore are able to be thrown far onto land. When approaching the shore, they are deformed and, rolling onto the shore, produce enormous destruction. In the open ocean, water monsters are not high, not exceeding 2–3 m in height during the strongest earthquakes, but at the same time they have a considerable length, sometimes reaching 200–300 km, and an incredible propagation speed.

Approaching the shore, depending on the coastal topography of the bottom and the shape of the coastline, giant waves can grow up to several tens of meters. Getting into the shallow coastal zone, the wave changes - its height increases and at the same time the steepness of the leading front increases. When approaching the shore, it begins to capsize, creating a foaming, bubbling, high-altitude water stream that falls on the shore. In such cases, the mouths of the rivers are quite dangerous, along which monstrous waves are able to penetrate deep into the territory for a distance of several kilometers.

Tsunami - consequences

1946, April 6 - The city of Hilo on the island of Hawaii experienced the full power of the perturbation of the water element. Residential buildings and administrative buildings were overturned, asphalt roads and beaches disappeared, the railway bridge was moved 300 m upstream, and stone blocks weighing several tons were scattered throughout the devastated area. This was the result of a displacement of the ocean floor, which occurred at a distance of 4,000 km from Hilo, in the region of the Aleutian Islands.

The shock gave rise to a series of tsunamis that rushed across the Pacific Ocean at a speed of over 1,100 km/h, reaching a height of 7.5 to 15 m. Waves of this kind propagate in all directions from the point where they originated, at great intervals, but at a frightening speed. While the distance between ordinary sea waves is about 100 m, tsunami wave crests follow each other with an interval of 180 km to 1200 km. Therefore, the passage of each such wave is accompanied by a deceptive lull.

That is why, when the first wave subsided in Hilo, many residents went down to the shore to understand the extent of the destruction, and were washed away by the next giant wave. An eyewitness account stated:

“Tsunami waves, steep and whirling, surged onto the shore. Between the ridges, the water receded from the coast, exposing reefs, coastal silt deposits and the bottom of the bay at a distance of up to 150 meters or more behind the usual coastline. The water rolled back rapidly and violently, with a whistle, hiss and roar. In several places, houses were washed away into the sea, in some places even huge rocks and concrete blocks were carried over the reefs. People, along with their belongings, were swept out to sea, and only a few of them managed to be rescued after a few hours with the help of boats and life rafts dropped from aircraft.

If the speed of a simple wind wave is capable of reaching 100 km/h, then tsunami waves move at the speed of a jet aircraft - from 900 to 1500 km/h. The deadly influence of the elements is determined not only by the power of the shock that gave rise to the tsunami, but also by the area along which the giant wave goes, and the distance from the coast.

Of course, they are more dangerous on gentle coasts than on steep ones. When the bottom is steep, the incoming waves will not rise to a sufficient height, but, flying into a gentle shore, they often reach the height of a six-story building or more. When these waves enter the bay or bay in the form of a funnel, each of them brings down a violent flood on the shore. The height of the wave decreases only in closed expanding bays with a narrow entrance, and when it enters the river, the wave increases in size, increasing its destructive power.

The activity of the volcano in the water column gives an effect that can be compared with a strong earthquake. The greatest giant wave ever known was caused by the powerful eruption of the Krakatoa volcano in Indonesia in 1883, when a huge mass of rock was thrown into the air to a height of several kilometers and turned into a dust cloud that circled our planet three times.

Chasing each other sea ​​waves heights up to 35 m drowned over 36,000 inhabitants of the nearest islands. They circled the whole Earth and a day later were observed in the English Channel. A military vessel off the coast of Sumatra was thrown 3.5 km into the interior of the island, where it got stuck in a thicket 9 m above sea level.

Another stunning case of an unusually high wave was recorded on July 9, 1958. After the earthquake in Alaska, the mass of ice and earth rocks with a volume of about 300 million cubic meters. m collapsed into the narrow and long Lituya Bay, causing a colossal wave surge on the opposite side of the bay, which reached almost 60 meters in certain parts of the coast. At that time, there were three small fishing boats in the bay.

“Despite the fact that the disaster occurred 9 km from the parking lot of the ships,” says an eyewitness, “everything looked terrible. Before the eyes of the shocked people, a huge wave rose up, swallowing the foot of the northern mountain. Then it swept across the bay, stripping trees from the slopes of the mountains, destroying the recently abandoned climbers' camp; having fallen like a water mountain on the island of Cenotaphia, it swallowed up the old hut and, in the end, rolled over the highest point of the island, which towered 50 m above sea level.

The wave spun Ulrich's ship, which, out of control, rushed at the speed of a galloping horse towards the ships of Swanson and Wagner, still at anchor. To the horror of the people, a wave broke the anchor chains and dragged both ships like chips, forcing them to overcome the most incredible way, which once fell to the lot of fishing boats. Under the ship, Swanson said, they saw the tops of 12-meter trees and rocks the size of a house. The wave literally threw people across the island into the open sea.

For centuries, tsunamis have become the culprits of terrible world catastrophes.

1737 - a case of a giant wave on the Kamchatka coast is described, when the waves washed away almost everything that was in the flood zone. A small number of victims was explained only by a small number of inhabitants.

1755 - due to the fault of a water monster, the city of Lisbon is completely wiped off the ground, the death toll is more than 40,000 people.

1883 - The tsunami caused enormous damage to the coasts of the Indian Ocean, the death toll was more than 30,000.

1896 - the water element hit the shores of Japan, the death toll is more than 25,000.

1933 - The coast of Japan suffered again, more than a thousand buildings were destroyed, 3,000 people died.

1946 - the most powerful tsunami caused great damage to the islands and the coast near the Aleutian sinkhole; the total loss is more than $20 million.

1952 - a furious ocean attacked the northern coast of Russia, and although the wave height was no more than 10 m, the damage was enormous.

1960 - the coast of Chile and nearby territories were hit by giant waves, the damage was more than $ 200 million.

1964 - coast Pacific Ocean was hit by a tsunami that destroyed buildings, roads and bridges worth more than $100,000.

In recent years, it has been established that even "space guests" - meteorites that did not have time to burn out in the earth's atmosphere, can cause giant waves. Maybe a few tens of millions of years ago, the fall of a giant meteorite led to a tsunami, which led to the death of dinosaurs. Another, quite banal reason, may be the wind. He is able to call big wave only under appropriate circumstances - the air pressure must be correct.

However, the most important thing is that a person is able to provoke a “man-made” tsunami himself. This is what the Americans proved in the middle of the 20th century by experiencing an underwater nuclear explosion, which caused huge underwater disturbances and, as a result, the appearance of monstrous high-speed waves. Be that as it may, even now a person cannot for sure predict the appearance of a tsunami and, what is even worse, stop it.

Tsunamis are huge sea waves that occur most often as a result of a strong underwater earthquake, when there is a rapid change in the bottom topography. It acts on the water like a huge piston, raising or lowering large masses of water, which, scattering in all directions, form waves. Less commonly, tsunamis occur as a result of the eruption of underwater or island volcanoes, when large masses of earth rocks collapse into the water and underwater landslides.

In the open ocean, tsunami waves propagate at speeds up to 1,000 kilometers per hour. But there they are very gentle, since the wavelength (the distance between the crests) reaches 100-300 kilometers, and the height from the bottom to the top is only a few meters, and therefore they are not dangerous for navigation. When waves enter shallow water, near the coastline, their speed decreases sharply to 50-100 kilometers per hour, and their height increases. Near the coast, a tsunami can reach several tens of meters. The highest waves, up to 30-40 meters, are formed near steep coasts, in wedge-shaped bays and near capes protruding far into the ocean. Coastal areas with closed bays are less dangerous.

Tsunami Warning System
The Pacific Tsunami Warning System (TWS) includes 25 states, including Russia, whose coastal areas are affected by tsunamis.

The Far East Tsunami Warning Service is interregional and consists of three regional services: Kamchatka, Sakhalin regions and Primorsky Krai. In the Kamchatka region, tsunami warning is carried out by the tsunami station of the Kamchatka Territorial Administration for Hydrometeorology and Monitoring environment and a seismic station of the Institute of Physics of the Earth, Russian Academy of Sciences.

The Pacific Tsunami Warning Center (TPTC) is located in the US Hawaiian Islands in Honolulu.

Remote earthquake warning
When a strong earthquake occurs in the Pacific Ocean, the Pacific Center informs all members of the SPC of the time, coordinates and strength of the earthquake. The first information about a tsunami comes from sea level observation stations located in close proximity to the epicenter of the earthquake. If confirmation of the formation of waves is received, then in the event of a destructive tsunami approach and to bring the operational services of the TCPC to a state of readiness, it transmits a warning.

The tsunami station, after analyzing this information and with a real threat of a tsunami to Kamchatka, announces an alarm.

Earthquake warning
In the event of a strong nearby earthquake off the coast of Kamchatka and a possible threat of a tsunami, the seismic station announces an alarm and transmits it according to the notification scheme. The tsunami station distributes this message throughout the region, as well as beyond its limits, performs calculations of tsunami parameters (height and time of arrival of waves), analyzes information about the observed heights of their waves received from hydrometeorological stations, and transmits an end to the alarm. The tsunami station also transmits information about the wave height on the peninsula to the TCTC, on the basis of which the Center makes an assessment of the tsunami hazard for other areas of the Pacific Ocean.

• Signs of a tsunami threat:
  
  
  • a strong earthquake with a force of 6 points or more - when the vibrations of the earth's surface make it difficult to walk, buildings stagger, sway strongly pendant lamps, dishes fall and break, objects fall from shelves, furniture can move. Strong fluctuations last 20 seconds or more;
  • a sudden rapid departure of water from the coast for a considerable distance and drying of the bottom, while the noise of the surf stops (do not try to go down to the water to check this!). The further the sea recedes, the higher the tsunami waves can be;
  • a rapid drop in sea level at high tide or a rise at low tide;
  • unusual drift of ice and other floating objects, formation of cracks in the fast ice;
  • huge reverse faults at the edges of immovable ice and reefs, the formation of crowds, currents.
• Action plan for your family.
• In case of evacuation, you should keep a flashlight, matches, some food, spare clothes, along with documents, packed in a backpack, at the ready.
• How to get to the nearest safe area.
• In populated areas, civil defense forces and other rescue teams will try to save your life. Help them in everything.

What to do in case of a tsunami threat

• If you are outside the warning zone or in hard-to-reach coastal areas, then when signs of a threat are detected, you should remember that tsunami waves can reach the coast 15-20 minutes after the earthquake starts. During this time, you must immediately take protective measures:
  
  
  • it is necessary to leave the coast inland to a hill where the height above sea level is 30-40 meters. If you are on the shore of a closed bay, then this height should be at least 5 meters; it is necessary to leave the coast up the slopes, and not along the river valleys, since the tsunami penetrates the farthest inland along the rivers;
  • in the absence of a hill nearby, it is necessary to move away from the coast by at least 2-3 kilometers.
• If within 1-2 hours after a strong earthquake the waves do not hit the shore, then the tsunami, as a rule, no longer threatens.
• You should not return to shore after the first wave earlier than 3 hours, as the first wave is usually followed by others, with the second and third waves reaching their greatest strength.
• Vessels located in coastal waters, standing in an open roadstead or in a bay with a wide entrance, and even more so at the berths, should go into the ocean beyond the 50-meter isobath; keep the course - perpendicular to the line of the coast.
• If your area has a public address system, wait for the alarm signal to end.

The rules of conduct during a tsunami need to be known to everyone who lives in an area where this natural phenomenon can occur. It is always worth remembering that it is fraught with the most devastating consequences.

What is a tsunami?

The main thing to remember is that if you follow the rules of conduct during a tsunami, then save the lives of yourself and your loved ones.

After all, this global It represents waves of great height that appear due to a powerful underwater earthquake. This usually happens during a change in the bottom topography. It acts on the water like a huge piston that raises and lowers large masses of water. Scattering to the sides, they form destructive waves.

Sometimes there are others. For example, it can appear due to the eruption of island, less often underwater volcanoes, as well as during the simultaneous collapse of large masses of earth rocks into the water. This happens during underwater landslides.

Spreading

The rules for a tsunami must be well remembered by everyone, because this natural disaster spreads very quickly. In the open ocean, the speed of a tsunami wave can reach thousands of kilometers. But there they are not as dangerous as on the coast, because they are more gentle.

The distance between the ridges can be from one hundred to three hundred kilometers. And the height from the sole to the top is only a few meters. Therefore, a tsunami almost never poses a danger to ships and ships. To know the rules of behavior during a tsunami should, first of all, the inhabitants of the coast.

The element is coming

When approaching the coast, the speed of the waves drops sharply, to about a few tens of kilometers per hour. But the height, on the contrary, increases. In shallow water, the height of a tsunami can increase up to forty meters. It is especially dangerous near steep coasts, as well as in wedge-shaped bays, near capes protruding far into the ocean.

Also, a tsunami can penetrate deep into the mainland, moving along river valleys. In their channels, the phenomenon of boron is formed. This is the name of a high water shaft that moves against the current. The least dangerous for the impact of a tsunami are coastal areas with closed bays.

Where do tsunamis occur?

It is now known for certain that the rules of conduct during a tsunami are most relevant for residents of the Pacific coast. After all, it is in this ocean that about 80% of the most powerful earthquakes occur. Therefore, the coast of Kamchatka is also considered to be the most affected by this element. Here, most residents clearly know the rules of conduct in case of a tsunami threat. Even if you don't live in these places, you should keep them in mind if you travel along the east coast of Russia.

Not far from these places there is a tsunamigenic zone, from where the most powerful waves come. It is located in the Aleutian and Kurile-Kamchatka trenches. Information about the tsunami in Kamchatka that occurred in 1737 has survived to this day.

Notification system

When it becomes known that an earthquake has occurred in the Pacific Ocean, the Pacific Center transmits the relevant information to all tsunami warning services. It becomes immediately known about the coordinates and strength of the earthquake, as well as the likelihood of a tsunami and its estimated strength.

The first to learn about the approaching tsunami at sea level observation stations. They are located in close proximity to the epicenter of the earthquake. When confirmation of the formation of waves of anomalous height is received, the inhabitants of the areas that they may affect receive a warning, all operational services are put on alert. At these moments, it is especially important to know the rules of behavior during a tsunami point by point.

When it becomes obvious that there is a real threat of the spread of high waves, an alarm is announced. Corresponding messages are received by all operational services. In the Kamchatka Territory, this happens with the help of a special "OXION" system. This modern system works in the fourteen most tsunami-prone settlements in Kamchatka. Operational services immediately bring information to the public. For this, in particular, there are radio broadcasting points, sirens, the loudspeakers briefly list, point by point, the rules of conduct during a tsunami.

Tsunami threats

It is important not only to focus on the messages of the operational rescue services, but also to be aware of the signs that may indicate the approach of this element.

The real threat of a tsunami exists when a powerful earthquake (at least 6 points) occurs. It is easy to define it. The oscillation of the earth's surface is so strong that it is difficult for a person to walk, buildings stagger, pendant lamps sway in apartments, dishes fall out of cabinets and break, objects fall from shelves, even powerful furniture can move around the house or office. Such strong oscillations should last at least 20 seconds.

Another sign of an approaching tsunami is considered to be a sudden departure of water from the coast for a considerable distance. This exposes the bottom. Remember, the further the sea receded, the higher and stronger the tsunami waves can be. It is also worth worrying if the sea level is too low at high tide and too high at low tide, the ice begins to drift in an unusual way, cracks form in the fast ice, floating objects move along an anomalous trajectory. In addition, it is worth paying attention to the formation of currents, reverse faults at the edges of immovable ice and reefs.

How to prepare for a tsunami?

To prevent a tsunami from taking you by surprise, you should always have on hand in an easily accessible place the items you need in case of an emergency evacuation. These are matches, a small amount of food, a flashlight, documents, spare clothes. All this should be packed in a reliable backpack or waterproof bag.

You also always need to evaluate which ways and means you can get to a safe place the fastest.

Tsunami Action

You should follow the rules of conduct during a tsunami so as not to get hurt. In coastal communities, upon receiving an alarm, you should immediately leave your homes and offices. It is necessary to leave the premises in accordance with the evacuation plan.

If you find yourself in the warning zone or in hard-to-reach areas, then you should remember that a tsunami can reach the coast within 10-20 minutes after the earthquake starts. This is the time you have to take the necessary protective measures.

You need to quickly move away from the coast into the depths of the land. It is best on a hill, so that the height above sea level is at least 30-40 meters. If you are in a closed bay, then the height may be limited to five meters. You should leave the coast along the slopes, and not along the river valleys.

If there is no elevation in the district, you need to move at least two or three kilometers from the coast. If two hours have passed since the earthquake, and the waves have not hit the shore, most likely the tsunami threat has passed. But it's best to wait for the all-clear signal if your area has a public address system.

If the tsunami wave has reached the coast, you should return to the coast no earlier than three hours later. Indeed, after the first wave, several more often follow.

Vessels that are in coastal waters must go to the open ocean, keeping a course perpendicular to the coastline.