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The earthquake and tsunami in the Indian Ocean in 2004

Underwater earthquake in the Indian Ocean, which occurred December 26, 2004, caused a tsunami, which was recognized as the most deadly natural disaster in modern history. The magnitude of the earthquake was, according to various estimates, from 9.1 to 9.3. This is the second or third on the strength of an earthquake in the history of observations. 

The epicenter was located in the Indian Ocean, just north of Simeulue island, located near the north-west coast of Sumatra Island (Indonesia). The tsunami reached the coast of Indonesia, Sri Lanka, southern India, Thailand and other countries. Wave height exceeds 15 meters. The tsunami resulted in enormous destruction and a huge number of people killed, even in Port Elizabeth in South Africa, 6900 km from the epicenter. 

Died, according to various estimates, from 225,000 to 300,000 people. According to the U.S. Geological Survey (USGS), the number of deaths - 227 898. The true death toll is unlikely to ever be known, since many people were blown to sea water. 

Hypocenter of the earthquake was the main point with the coordinates of 3,316 °. m., 95,854 ° c. etc. (3 ° 19 's. w., 95 ° 51,24' in the. etc.) at a distance of about 160 km west of Sumatra at a depth of 30 km above sea level (initially reported 10 km from sea level .) This is the western end of the Pacific Ring of Fire, earthquake zone, which occurs up to 81% of the largest earthquakes in the world. 

The earthquake was unusually large in geographical terms. A shift of about 1200 km (according to some estimates - 1600 km) of rocks at a distance of 15 meters along the subduction zone, resulting in chegoIndiyskaya plate moved under the Burma plate. The shift was not a one-time, and was divided into two phases within a few minutes. Seismographic data suggest that the first phase sformirovalarazlom size of approximately 400 km by 100 km, is located at about 30 km above sea level. Rift was formed at a rate of about 2 km / s, starting from the shore side of the ASE in the north-west for about 100 seconds. Then came a pause of about 100 seconds, after which the fault continued to be formed on the north side of the Andaman and Nicobar Islands. 

The Indian plate - a large part of the Indo-Australian plate, which lines the Indian Ocean and Bay of Bengal, moving northeast at an average speed of 6 cm per year. The India Plate meets the Burma Plate, which is considered part of the great Eurasian Plate), forming the Sunda Trench. At this point the Indian plate moves up under the Burma plate, on which the Nicobar Islands, Andaman Islands and the northern part of Sumatra island. Indian plate slowly slides deeper and deeper beneath the Burma Plate until the increasing temperature and increasing pressure does not turn push the edge of the Indian plate in the magma, which eventually is thrown up by volcanoes (called volcanic arc). This process is interrupted because of the clutch plates for several centuries, until the pressure will not be forced by reason of a major earthquake and tsunami. 

When the movement of tectonic plates and the sea floor rises by several meters, thus giving rise to the devastating tsunami waves. At the center of the tsunami is not a point as such, mistakenly assume that the illustrations of their spread. Tsunamis propagate radially from the entire fault length of about 1200 km. It is for this reason that the tsunami waves were so strong that it even reached Mexico and Chile. 

Several subsequent after shocks have been recorded near the Andaman and Nicobar Islands, as well as near the epicenter in the next few hours after the first earthquake, and days. The highest recorded intensity was equal to 7.1 (near the Nicobar Islands). The other tremors with magnitude up to 6.6 points continued to occur in the vicinity of the epicenter of nearly every day. 

The earthquake occurred three days after the earthquake of 8.1 in a desert area located west of New Zealand's Auckland Islands and north of Australia's Macquarie Island. This is very unusual, since earthquakes of magnitude 8 or more points occur on average less than once a year. Some seismologists say about the relationship between these two earthquakes, saying that the more recent of which was provoked by the first, since both earthquakes occurred on opposite sides of the Indo-Australian tectonic plate. However, USGS sees no connection between them. 

Coincidentally, the earthquake occurred exactly one year (up to an hour) after the earthquake of 6.6 magnitude that occurred in Bam in Iran. 

As aftershocks, the energy released by the first earthquake, continued to operate, a week after the earthquake still recorded fluctuations, providing important scientific data about the guts of the earth. 

The total energy released by an earthquake in the Indian Ocean, estimated to be about 2 ekzadzhoulya (2,0 × 18 October joules). This is enough energy to boil 150 liters of water every inhabitant of the Earth, or the same amount of energy used by mankind for 2 years. It is assumed that the surface of the Earth made a fluctuation in the range of 20-30 cm, which is equivalent to the tidal forces exerted by the Sun and the Moon. A shock wave went through the earthquake the whole planet, in the U.S., shtateOklahoma were recorded in the vertical oscillations of 3 mm. 

The shift of mass and a huge burst of energy only slightly altered the Earth's rotation. The exact figure is not defined yet, but theoretical models suggest that the earthquake decreased the length of the day by about 2.68 microseconds (2.68 ms), that is, about one-billionth of a flattening due to the decrease of the Earth. The earthquake also led to the so-called. minute "wobble" of the Earth around its own axis by 2.5 cm in the direction of 145 ° east longitude, or possibly even 5 or 6 cm, however, influenced by the tidal forces of the moon, the length of day increases on average by 15 ms every year, so that any increase in speed quickly disappear. In addition, the natural swaying of the earth from its axis can be up to 15 m 

More impressive is that some small island to the south-west of Sumatra, were shifted to the southwest at a distance of 20 meters. The northern end of Sumatra, which is located on the Burma plate (southern Sunda Plate), can also be shifted by 36 meters to the southwest. The shift has been both vertical and lateral, some coastal areas are now below sea level.Measurements made with the help of GPS and satellite photos give an idea of how much has changed geophysical situation. 

Sharp vertical jolts the seabed by several meters during the earthquake caused the displacement of huge masses of water, which resulted in a tsunami, which reached the coasts of the Indian Ocean. Tsunamis causing damage far away from their places of origin, usually referred to as "teletsunami" and they often arise from the vertical displacement of the seabed, rather than the horizontal displacement. 

It's a tsunami, like others, behaves in the deep parts of the ocean quite differently than in shallow water. In the deepest part of the tsunami waves appear as a small bump just visible, but harmless-looking, and they move very fast (500-1000 km / h) in shallow water, near the shores of a tsunami slows down to tens of kilometers per hour, but This form huge destructive waves. 

Radar satellites recorded the heights of tsunami waves in the deep ocean, two hours after the earthquake, the maximum wave height reached 60 cm This is the first measurement of such complexity in history. 

According to Ted Mert, Vice President of the Company's tsunami, the total energy of the tsunami waves was comparable to five megatons of TNT (20 petajoules). This is more than twice larger than the energy of live ammunition, exploded during the Second World War (including the two atomic bombs dropped on Hiroshima and Nagasaki), but by orders of magnitude smaller than the energy released by an earthquake. In many places, the waves were up to 2 km of land, and in some (particularly in the coastal gorodeBanda Aceh) - 4 km. 

Since the break of 1200 kilometers was located approximately north-south direction, the greatest force of the tsunami wave reached the east-west. Bangladesh, situated at the northern end of the Bay of Bengal, has received the slightest injury, even though that is far enough above sea level. 

Coast, which have a natural barrier to the Earth's tsunami waves, most of them were left unexposed, however, tsunami waves can sometimes diffract around such earth barriers.Thus, the Indian state of Kerala affected by the tsunami, although it is located on the west coast of India, west coast of Sri Lanka is also strongly affected by the tsunami. In addition, a large distance from the place of the waves and does not guarantee security; Somalia has suffered far more than Bangladesh, although it is much further. 

Depending on the distance, the time it took the tsunami to reach the coast, it was from 50 minutes to 7 hours (in the case of Somalia). The northern regions of the Indonesian island of Sumatra, met with a tsunami is very fast, and Sri Lanka and the east coast of India - but after a time from 90 minutes to 2 hours later. Thailand is also a wave overtook two hours later, although he was closer to the epicenter - the reason being that the tsunami was moving slowly in the shallow waters of the Andaman Sea. 

In Struisbaai (South Africa), which is about 8500 km from the earthquake, 16 hours after the incident were recorded tidal wave height of 1.5 m relatively long time dohozhdeniya waves up to this most southern point of Africa can be explained by the nature of the continental shelf off the southern coast of Africa and the fact that the tsunami had to follow all of the southern coast from east to west. 

A certain amount of energy it took the tsunami to the Pacific Ocean, resulting in a small but noticeable (to measure) tsunamis along the western coasts of North and South America (an average height of 20-40 cm). In Manzanillo (Mexico) noted the wave height of 2.6 m Some experts say that this is a relatively large tsunami at that distance was caused by a combination of the effects of the Pacific Ocean and the local geography. 

Data on the number of victims of the earthquake, tsunami and subsequent flooding vary considerably because of the confusion and contradictory news from the field. The total number of victims is estimated at 235,000 people, tens of thousands are missing, more than a million people were left homeless. Originally reported losses, measured in hundreds of human lives, but for the next week the number of known victims has risen dramatically. 
Charitable organizations have reported that approximately one third of the victims - children.This is a result of the high proportion of children in communities affected by the cataclysm of many of the regions and the fact that children were the least able to resist the coming waters. 

In addition to the huge number of local residents, more than 9,000 foreign tourists (mostly Europeans) while holidaying in the regions affected by the tsunami, killed or missing. 

The critical situation was declared in Sri Lanka, Indonesia and the Maldives. The United Nations declared that the current rescue operation will be the most costly of all ever held. UN Secretary General Kofi Annan said that the reconstruction will take five to ten years.Government and non-governmental organizations feared that the final death toll could double as a result of disease. 

According to the number of victims of the earthquake was one of the 10 most destructive in history. It is also one of the worst tsunami in history, the previous "record" belonged to the tsunami in 1703 in the Awa (Japan), which killed about 100,000 people. 
 
Countries most affected by this natural disaster
The countries most affected by this natural disaster
 

 

Автор: admin от 05.03.2012





  

 

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