Earthquake and Tsunami
The history of mankind takes several millennia. While analyzing it in the human terms, it is a large period of time, but in the cosmic or geological terms, it is not even a moment. Disasters such as volcanic eruptions, powerful earthquakes, tornadoes, etc. are known since ancient times, and the modern world is not an exception. Each year there occur a great number of disasters that lead to human deaths as well as other negative outcomes. The key goal of modern scientists, as well as emergency agencies, is to predict disasters as well as minimize the possible harmful effects based on the previous disaster experience.
Thus, taking into account all the mentioned above, the following paper will discuss the Indian Ocean earthquake and tsunami which occurred in South East Asia on December 26, 2004, and was marked as a tragedy of immense proportions. It brought suffering to a huge number of people and causing various deaths and injuries. In fact, on December 26, 2004 at 00:58 on the Coordinated Universal Time (07:58 a.m. local time) in the depths of the Indian Ocean, near the Indonesian island of Simeulue, there occurred the strong earthquake with the magnitude from 9.1 to 9.3 points. It gave rise to a series of killer waves that brought huge destructions on the coast of Asia and within a few hours killed about 300 thousand people.
The undersea earthquake in the Indian Ocean caused a tsunami on December 26, 2004 at 00:58:53 UTC, which was considered the deadliest natural disaster in modern history. According to various estimates, the magnitude of the earthquake was from 9.1 to 9.3 is one of the three strongest earthquakes in the history of observations (West et al., 2005).
The epicenter was in the Indian Ocean to the north of the island of Simeulue located near the north-western coast of the island of Sumatra (Indonesia). The tsunami reached the shores of Sri Lanka, Indonesia, Southern India, Thailand, and other countries with waves more than 15 meters high. The tsunami resulted in terrible destruction and a huge number of human losses. In fact, according to various estimates, from 225 to 300 thousand people were killed by the disaster. According to the US Geological Survey (USGS), the number of deaths is 227 898. The true death toll is unlikely to ever be known since many people were carried out with water into the ocean (Jayasuriya, McCawley, 2010).
Initially, the earthquake to the north of the island of Simeulue was measured at 6.8 magnitudes on the Richter scale. The PTWC (Pacific Ocean Tsunami Warning Center) estimated its magnitude at 8.5 immediately after the incident. However, the moment magnitude, which more accurately assessed the earthquake was estimated as 8.1 points on the Richter scale. The further assessment showed the gradual increase of the magnitude up to 9.0 points on the Richter scale. Later, in February 2005, the strength of the earthquake was estimated at 9.3 points. However, it should be mentioned that although PTWC accepted this new assessment, the USGS still regards the earthquake as a 9.1 point magnitude on the Richter scale (Lay et al., 2004).
The hypocenter of the main earthquake was located at a distance of about 160 km to the west of Sumatra at a depth of about 10-30 km below sea level. The area belonged to the western end of the Pacific ring of fire, i.e. the earthquake zone, which produces up to 81% of the largest earthquakes in the world.
The earthquake was unusually large in a geographical sense. There was a shift of about 1200 km (according to some estimates up to 1,600 km) of rocks over a distance of 15 m along the subduction zone resulting in the movement of the Indian plate under the Burma plate. The offset was not lumped, but it was divided into two phases within a few minutes. The seismographic data suggest that the first phase formed the fracture dimensions of approximately 400 km by 100 km located about 30 km below the sea level. The rift was formed at a rate of about 2 km / s from the coast towards the northwest for about 100 seconds. Then there was a pause of about 100 seconds followed by the break formed on the north side of the Andaman and Nicobar Islands (Nalbant et al., 2005).
The Indian plate is supposed to be a large part of the Indo-Australian Plate, which lines the Bay of Bengal and the Indian Ocean moving to the northeast at an average speed of 6 cm per year. In fact, the dramatic advancement of tectonic plates as the seabed raised for several meters, thereby giving rise to destructive tsunami waves, propagating from the entire fracture length for about 1,200 km (McKee, 2005).
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Several subsequent aftershocks have been reported near the Andaman and Nicobar Islands as well as in the epicenter area in the next few hours and days after the earthquake. The highest recorded magnitude was 7.1 (near the Nicobar Islands). The rest of the aftershocks of 6.6 magnitudes were noticed in the epicenter of the area almost every day after the accident.
In fact, the shift of the masses and a huge amount of the released energy has changed the Earth’s rotation speed. The exact figure has not been determined, but theoretical models allow assuming that the earthquake decreased the length of day for about 2.68 microseconds (2.68 ms) which is about one-billionth due to the decrease of the Earth’s oblateness. The earthquake also caused a so-called minute of “wobble” on the Earth around its axis by 2.5 cm in the direction of 145 ° east. However, under the influence of the tidal forces of the Moon, the duration of the day increases by an average of 15 microseconds each year so that any increase in the speed of rotation will quickly disappear. In addition, the natural swaying of the Earth from its axis can be up to 15 m.
In addition, some small islands to the south-west of Sumatra were shifted to the south-west at a distance of 20 meters. The northern end of Sumatra, which is on the Burma plate (southern regions of the Sunda Plate), may also be shifted by 36 meters to the south-west. 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 pictures give an idea of how much geophysical situation has changed (Walton, 2005).
Tsunami often causes damage far away from their places of origin so that they are more likely to arise from the vertical displacement of the seafloor rather than the horizontal displacement.
This tsunami, like the others, behaved in the deep parts of the ocean quite differently than in the shallow water. The deep part of the tsunami wave looks like a small noticeable bump but with a harmless mind; while it moves at a very high speed (500-1000 km / h) in shallow waters near the coasts, the tsunami slows down to tens of kilometers per hour at the same time forming huge destructive waves. Radars recorded the tsunami waves’ height within the deep ocean; two hours after the earthquake, the maximum wave height reached 60 cm. This is the first measurement of such an issue in the history (Satake, Atwater, 2007).
The total energy of the tsunami waves was comparable to five megatons of TNT. This is more than two times greater than the energy of ammunition bombed during World War II (including the bombs dropped on Hiroshima and Nagasaki) but by orders of magnitude smaller than the energy released by an earthquake. In many places, the waves went up to 2 km of land, and in some (particularly in the coastal city of Banda Aceh) – 4 km (Paris et al., 2007).
Since 1200 kilometers break was located approximately in the north-south direction, the devastating force of the tsunami waves reached the east-west direction. Bangladesh located on the northern end of the Bay of Bengal has received the most minor injuries despite the fact that it is on the low altitude.
The coast, which is a natural barrier to the earth tsunami waves, for the most part remained unmoved. However, tsunami waves can sometimes diffract around obstacles such as earth. Various governmental and non-governmental organizations including UNICEF, Red Cross, WHO, etc. helped to manage the results of the disaster.
The reported number of victims of the earthquake, tsunami, and subsequent flooding vary greatly due to the confusion and conflicting news from the field. About 235 thousand people became the victims of the tsunami, while tens of thousands got missed. More than a million people were left homeless. The reported number of losses included hundreds of human lives, but in a week after the disaster, the number of known victims has risen even more dramatically. On the south-west coast of Sri Lanka, waves 7-9 meters high located near the coast destroyed a crowded passenger train «Samudra Devi», which killed about 1,700 people – the largest train accident in world history (BBC News, 2005). Charitable organizations have reported that about a third of the victims were children.
In addition, more than 9,000 foreign tourists (mostly Europeans) as well as a large number of local residents have been affected by the tsunami, i.e. killed or missing, particularly affected tourists from Scandinavian countries. In fact, Sweden reported about 1,300 missing people and 60 dead. The most critical situation has been noticed in Indonesia, Sri Lanka, and the Maldives. The UN has announced that the current rescue operation will be the most expensive of all ever held. The various non-governmental and governmental organizations were afraid of the increased death ratio due to the likelihood of the disease spread.
The lessons of the Indian Ocean earthquake and tsunami proved the necessity and importance of the early prediction of the cataclysm occurrence for modern society.
Many countries, which have been affected by the tsunami, are now much better prepared for possible natural disasters. However, it should be mentioned that there is no natural disaster which is an exact replica of its predecessors. Nevertheless, the experience of Indonesia that survived the tsunami in 2004 may be useful for the authorities and humanitarian organizations in Japan.
The experience has proved that it is virtually impossible to convince people to leave their homes. Therefore, the government should try to minimize the risk in case of a new tsunami through the introduction of an effective early warning system in disaster-prone regions of the fortified building, where one can take shelter and, of course, be constantly on the alert.
By the end of 2005, the various organizations and governments issued a report about what they have achieved during the year in terms of providing assistance to the affected region. The United Nations Foundation made another step forward distinguishing the lessons of the tragedy that could help the world to respond more effectively to new catastrophes. The report stresses the importance of providing emergency funding immediately after the tragedy and emphasizes that the UN agency of the Central Emergency Response Fund will improve response to emergency humanitarian crises. The fund will provide a mechanism for urgent funding assistance as soon as it becomes necessary.
Among other lessons mentioned in the report of the UN Foundation, there is the coordination in providing assistance to organizations and institutions, the private sector contribution, the need for early warning, and the need for public consultation systems.
December 26, 2004 was marked as a tragedy bringing suffering to a huge number of people and causing numerous deaths and injuries. The depths of the Indian Ocean, near the Indonesian island of Simeulue produced a strong earthquake with the magnitude from 9.1 to 9.3 points. It gave rise to a series of killer waves that brought huge destructions on the coast of Asia and within a few hours killed about 300 thousand people. However, the lessons of the Indian Ocean earthquake and tsunami 2004 proved the necessity and importance of the early prediction of the cataclysm occurrence for modern society.
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