|Date||26 December 2004|
|Origin time||00:58 UTC
|Depth||30 km (19 mi)|
|Max. intensity||IX (Violent)|
|Tsunami||51 metres (200 ft)|
|Casualties||230,000–280,000 dead and more missing|
The 2004 Indian Ocean earthquake occurred at 00:58:53 UTC on 26 December with the epicentre off the west coast of Sumatra, Indonesia. The shock had a moment magnitude of 9.1–9.3 and a maximum Mercalli intensity of IX (Violent). The undersea megathrust earthquake was caused when the Indian Plate was subducted by the Burma Plate and triggered a series of devastating tsunamis along the coasts of most landmasses bordering the Indian Ocean, killing 230,000 people in 14 countries, and inundating coastal communities with waves up to 30 metres (100 ft) high. It was one of the deadliest natural disasters in recorded history. Indonesia was the hardest-hit country, followed by Sri Lanka, India, and Thailand.
It is the third-largest earthquake ever recorded on a seismograph and had the longest duration of faulting ever observed, between 8.3 and 10 minutes. It caused the entire planet to vibrate as much as 1 centimetre (0.4 inches) and triggered other earthquakes as far away as Alaska. Its epicentre was between Simeulue and mainland Indonesia. The plight of the affected people and countries prompted a worldwide humanitarian response. In all, the worldwide community donated more than US$14 billion (2004) in humanitarian aid. The event is known by the scientific community as the Sumatra–Andaman earthquake. The resulting tsunami was given various names, including the 2004 Indian Ocean tsunami, South Asian tsunami, Indonesian tsunami, the Christmas tsunami and the Boxing Day tsunami.
|2004 Indian Ocean
Animation of tsunami caused by the earthquake showing how it
The earthquake was initially documented as moment magnitude 8.8. In February 2005 scientists revised the estimate of the magnitude to 9.0. Although the Pacific Tsunami Warning Center has accepted these new numbers, the United States Geological Survey has so far not changed its estimate of 9.1. The most recent studies in 2006 have obtained a magnitude of Mw 9.1–9.3. Dr. Hiroo Kanamori of the California Institute of Technology believes that Mw 9.2 is a good representative value for the size of this great earthquake.
The hypocentre of the main earthquake was approximately 160 km (100 mi) off the western coast of northern Sumatra, in the Indian Ocean just north of Simeulue island at a depth of 30 km (19 mi) below mean sea level (initially reported as 10 km (6.2 mi)). The northern section of the Sunda megathrust ruptured over a length of 1,300 km (810 mi). The earthquake (followed by the tsunami) was felt simultaneously in Bangladesh, India, Malaysia, Myanmar, Thailand, Singapore and the Maldives. Splay faults, or secondary "pop up faults", caused long, narrow parts of the sea floor to pop up in seconds. This quickly elevated the height and increased the speed of waves, causing the complete destruction of the nearby Indonesian town of Lhoknga.
Indonesia lies between the Pacific Ring of Fire along the north-eastern islands adjacent to New Guinea, and the Alpide belt that runs along the south and west from Sumatra, Java, Bali, Flores to Timor.
Great earthquakes such as the Sumatra-Andaman event, which are invariably associated with megathrust events in subduction zones, have seismic moments that can account for a significant fraction of the global earthquake moment across century-scale time periods. Of all the seismic moment released by earthquakes in the 100 years from 1906 through 2005, roughly one-eighth was due to the Sumatra-Andaman event. This quake, together with the Good Friday earthquake (Alaska, 1964) and the Great Chilean earthquake (1960), account for almost half of the total moment. The much smaller but still catastrophic 1906 San Francisco earthquake is included in the diagram for perspective. Mw denotes the magnitude of an earthquake on the moment magnitude scale.
Since 1900 the only earthquakes recorded with a greater magnitude were the 1960 Great Chilean earthquake (magnitude 9.5) and the 1964 Good Friday earthquake in Prince William Sound (9.2). The only other recorded earthquakes of magnitude 9.0 or greater were off Kamchatka, Russia, on 4 November 1952 (magnitude 9.0) and Tōhoku, Japan (magnitude 9.0) in March 2011. Each of these megathrust earthquakes also spawned tsunamis in the Pacific Ocean. However, the death toll from these was significantly lower, primarily because of the lower population density along the coasts near affected areas and the much greater distances to more populated coasts and also due to the superior infrastructure and warning systems in MEDCs (More Economically Developed Countries) such as Japan.
Other very large megathrust earthquakes occurred in 1868 (Peru, Nazca Plate and South American Plate); 1827 (Colombia, Nazca Plate and South American Plate); 1812 (Venezuela, Caribbean Plate and South American Plate) and 1700 (western North America, Juan de Fuca Plate and North American Plate). All of them are believed to be greater than magnitude 9, but no accurate measurements were available at the time.
The megathrust earthquake was unusually large in geographical and geological extent. An estimated 1,600 kilometres (1,000 mi) of fault surface slipped (or ruptured) about 15 metres (50 ft) along the subduction zone where the Indian Plate slides (or subducts) under the overriding Burma Plate. The slip did not happen instantaneously but took place in two phases over a period of several minutes:
The Indian Plate is part of the great Indo-Australian Plate, which underlies the Indian Ocean and Bay of Bengal, and is drifting north-east at an average of 6 centimetres per year (2.4 inches per year). The India Plate meets the Burma Plate (which is considered a portion of the great Eurasian Plate) at the Sunda Trench. At this point the India Plate subducts beneath the Burma Plate, which carries the Nicobar Islands, the Andaman Islands, and northern Sumatra. The India Plate sinks deeper and deeper beneath the Burma Plate until the increasing temperature and pressure drive volatiles out of the subducting plate. These volatiles rise into the overlying plate causing partial melting and the formation of magma. The rising magma intrudes into the crust above and exits the Earth's crust through volcanoes in the form of a volcanic arc. The volcanic activity that results as the Indo-Australian Plate subducts the Eurasian Plate has created the Sunda Arc.
As well as the sideways movement between the plates, the sea floor is estimated to have risen by several metres, displacing an estimated 30 cubic kilometres (7.2 cu mi) of water and triggering devastating tsunami waves. The waves did not originate from a point source, as was inaccurately depicted in some illustrations of their paths of travel, but rather radiated outwards along the entire 1,600-kilometre (1,000 mi) length of the rupture (acting as a line source). This greatly increased the geographical area over which the waves were observed, reaching as far as Mexico, Chile, and the Arctic. The raising of the sea floor significantly reduced the capacity of the Indian Ocean, producing a permanent rise in the global sea level by an estimated 0.1 millimetres (0.004 in).
Numerous aftershocks were reported off the Andaman Islands, the Nicobar Islands and the region of the original epicentre in the hours and days that followed. The magnitude 8.7 2005 Nias–Simeulue earthquake, which originated off the coast of the Sumatran island of Nias, is not considered an aftershock, despite its proximity to the epicenter, and was most likely triggered by stress changes associated with the 2004 event. This earthquake was so large that it produced its own aftershocks (some registering a magnitude of as great as 6.1) and presently ranks as the 7th largest earthquake on record since 1900.
Other aftershocks of up to magnitude 6.6 continued to shake the region daily for up to three or four months. As well as continuing aftershocks, the energy released by the original earthquake continued to make its presence felt well after the event. A week after the earthquake, its reverberations could still be measured, providing valuable scientific data about the Earth's interior.
The 2004 Indian Ocean earthquake came just three days after a magnitude 8.1 earthquake in an uninhabited region west of New Zealand's subantarctic Auckland Islands, and north of Australia's Macquarie Island. This is unusual, since earthquakes of magnitude 8 or more occur only about once per year on average. However, the U.S. Geological Survey sees no evidence of a causal relationship between these events.
The December earthquake is thought to have triggered activity in both Leuser Mountain and Mount Talang, volcanoes in Aceh province along the same range of peaks, while the 2005 Nias–Simeulue earthquake had sparked activity in Lake Toba, an ancient crater in Sumatra.
The energy released on the Earth's surface only (ME, which is the seismic potential for damage) by the 2004 Indian Ocean earthquake and tsunami was estimated at 1.1×1017 joules, or 26 megatons of TNT. This energy is equivalent to over 1500 times that of the Hiroshima atomic bomb, but less than that of Tsar Bomba, the largest nuclear weapon ever detonated. However, the total work done MW (and thus energy) by this quake was 4.0×1022 joules (4.0×1029 ergs), the vast majority underground. This is over 360,000 times more than its ME, equivalent to 9,600 gigatons of TNT equivalent (550 million times that of Hiroshima) or about 370 years of energy use in the United States at 2005 levels of 1.08×1020 J.
The earthquake generated a seismic oscillation of the Earth's surface of up to 20–30 cm (8–12 in), equivalent to the effect of the tidal forces caused by the Sun and Moon. The shock waves of the earthquake were felt across the planet; as far away as the U.S. state of Oklahoma, where vertical movements of 3 mm (0.12 in) were recorded. By February 2005, the earthquake's effects were still detectable as a 20 µm (0.02 mm; 0.0008 in) complex harmonic oscillation of the Earth's surface, which gradually diminished and merged with the incessant free oscillation of the Earth more than 4 months after the earthquake.
Because of its enormous energy release and shallow rupture depth, the earthquake generated remarkable seismic ground motions around the globe, particularly due to huge Rayleigh (surface) elastic waves that exceeded 1 cm (0.4 in) in vertical amplitude everywhere on Earth. The record section plot displays vertical displacements of the Earth's surface recorded by seismometers from the IRIS/USGS Global Seismographic Network plotted with respect to time (since the earthquake initiation) on the horizontal axis, and vertical displacements of the Earth on the vertical axis (note the 1 cm scale bar at the bottom for scale). The seismograms are arranged vertically by distance from the epicenter in degrees. The earliest, lower amplitude, signal is that of the compressional (P) wave, which takes about 22 minutes to reach the other side of the planet (the antipode; in this case near Ecuador). The largest amplitude signals are seismic surface waves that reach the antipode after about 100 minutes. The surface waves can be clearly seen to reinforce near the antipode (with the closest seismic stations in Ecuador), and to subsequently encircle the planet to return to the epicentral region after about 200 minutes. A major aftershock (magnitude 7.1) can be seen at the closest stations starting just after the 200 minute mark. This aftershock would be considered a major earthquake under ordinary circumstances, but is dwarfed by the mainshock.
The shift of mass and the massive release of energy very slightly altered the Earth's rotation. The exact amount is not yet known, but theoretical models suggest the earthquake shortened the length of a day by 2.68 microseconds, due to a decrease in the oblateness of the Earth. It also caused the Earth to minutely "wobble" on its axis by up to 2.5 cm (1 in) in the direction of 145° east longitude, or perhaps by up to 5 or 6 cm (2.0 or 2.4 in). However, because of tidal effects of the Moon, the length of a day increases at an average of 15 µs per year, so any rotational change due to the earthquake will be lost quickly. Similarly, the natural Chandler wobble of the Earth, which in some cases can be up to 15 m (50 ft), will eventually offset the minor wobble produced by the earthquake.
More spectacularly, there was 10 m (33 ft) movement laterally and 4–5 m (13–16 ft) vertically along the fault line. Early speculation was that some of the smaller islands south-west of Sumatra, which is on the Burma Plate (the southern regions are on the Sunda Plate), might have moved south-west by up to 36 m (120 ft), but more accurate data released more than a month after the earthquake found the movement to be about 20 cm (8 in). Since movement was vertical as well as lateral, some coastal areas may have been moved to below sea level. The Andaman and Nicobar Islands appear to have shifted south-west by around 1.25 m (4 ft 1 in) and to have sunk by 1 m (3 ft 3 in).
In February 2005, the Royal Navy vessel HMS Scott surveyed the seabed around the earthquake zone, which varies in depth between 1,000 and 5,000 m (550 and 2,730 fathoms; 3,300 and 16,400 ft). The survey, conducted using a high-resolution, multi-beam sonar system, revealed that the earthquake had made a huge impact on the topography of the seabed. 1,500-metre-high (5,000 ft) thrust ridges created by previous geologic activity along the fault had collapsed, generating landslides several kilometres wide. One such landslide consisted of a single block of rock some 100 m high and 2 km long (300 ft by 1.25 mi). The momentum of the water displaced by tectonic uplift had also dragged massive slabs of rock, each weighing millions of tons, as far as 10 km (6 mi) across the seabed. An oceanic trench several kilometres wide was exposed in the earthquake zone.
The TOPEX/Poseidon and Jason-1 satellites happened to pass over the tsunami as it was crossing the ocean. These satellites carry radars that measure precisely the height of the water surface; anomalies of the order of 50 cm (20 in) were measured. Measurements from these satellites may prove invaluable for the understanding of the earthquake and tsunami. Unlike data from tide gauges installed on shores, measurements obtained in the middle of the ocean can be used for computing the parameters of the source earthquake without having to compensate for the complex ways in which close proximity to the coast changes the size and shape of a wave.
The sudden vertical rise of the seabed by several metres during the earthquake displaced massive volumes of water, resulting in a tsunami that struck the coasts of the Indian Ocean. A tsunami that causes damage far away from its source is sometimes called a teletsunami and is much more likely to be produced by vertical motion of the seabed than by horizontal motion.
The tsunami, like all others, behaved very differently in deep water than in shallow water. In deep ocean water, tsunami waves form only a small hump, barely noticeable and harmless, which generally travels at a very high speed of 500 to 1,000 km/h (310 to 620 mph); in shallow water near coastlines, a tsunami slows down to only tens of kilometres per hour but, in doing so, forms large destructive waves. Scientists investigating the damage in Aceh found evidence that the wave reached a height of 24 metres (80 ft) when coming ashore along large stretches of the coastline, rising to 30 metres (100 ft) in some areas when traveling inland.
Radar satellites recorded the heights of tsunami waves in deep water: at two hours after the earthquake, the maximum height was 60 centimetres (2 ft). These are the first such observations ever made. Unfortunately these observations could not be used to provide a warning, since the satellites were not built for that purpose and the data took hours to analyze.
According to Tad Murty, vice-president of the Tsunami Society, the total energy of the tsunami waves was equivalent to about five megatons of TNT (20 petajoules). This is more than twice the total explosive energy used during all of World War II (including the two atomic bombs) but still a couple of orders of magnitude less than the energy released in the earthquake itself. In many places the waves reached as far as 2 km (1.2 mi) inland.
Because the 1,600 km (1,000 mi) fault affected by the earthquake was in a nearly north-south orientation, the greatest strength of the tsunami waves was in an east-west direction. Bangladesh, which lies at the northern end of the Bay of Bengal, had very few casualties despite being a low-lying country relatively near the epicenter. It also benefited from the fact that the earthquake proceeded more slowly in the northern rupture zone, greatly reducing the energy of the water displacements in that region.
Coasts that have a landmass between them and the tsunami's location of origin are usually safe; however, tsunami waves can sometimes diffract around such landmasses. Thus, the state of Kerala was hit by the tsunami despite being on the western coast of India, and the western coast of Sri Lanka suffered substantial impacts. Distance alone was no guarantee of safety, as Somalia was hit harder than Bangladesh despite being much farther away.
Because of the distances involved, the tsunami took anywhere from fifteen minutes to seven hours to reach the coastlines. The northern regions of the Indonesian island of Sumatra were hit very quickly, while Sri Lanka and the east coast of India were hit roughly 90 minutes to two hours later. Thailand was struck about two hours later despite being closer to the epicentre, because the tsunami traveled more slowly in the shallow Andaman Sea off its western coast.
The tsunami was noticed as far as Struisbaai in South Africa, some 8,500 km (5,300 mi) away, where a 1.5 m (5 ft) high tide surged on shore about 16 hours after the earthquake. It took a relatively long time to reach this spot at the southernmost point of Africa, probably because of the broad continental shelf off South Africa and because the tsunami would have followed the South African coast from east to west. The tsunami also reached Antarctica, where tidal gauges at Japan's Showa Base recorded oscillations of up to a metre (3 ft 3 in), with disturbances lasting a couple of days.
Some of the tsunami's energy escaped into the Pacific Ocean, where it produced small but measurable tsunamis along the western coasts of North and South America, typically around 20 to 40 cm (7.9 to 15.7 in). At Manzanillo, Mexico, a 2.6 m (8 ft 6 in) crest-to-trough tsunami was measured. As well, the tsunami was large enough to be detected in Vancouver, British Columbia, Canada. This puzzled many scientists, as the tsunamis measured in some parts of South America were larger than those measured in some parts of the Indian Ocean. It has been theorized that the tsunamis were focused and directed at long ranges by the mid-ocean ridges which run along the margins of the continental plates.
Despite a lag of up to several hours between the earthquake and the impact of the tsunami, nearly all of the victims were taken completely by surprise. There were no tsunami warning systems in the Indian Ocean to detect tsunamis or to warn the general populace living around the ocean. Tsunami detection is not easy because while a tsunami is in deep water it has little height and a network of sensors is needed to detect it. Setting up the communications infrastructure to issue timely warnings is an even bigger problem, particularly in a relatively poor part of the world.
Tsunamis are much more frequent in the Pacific Ocean because of earthquakes in the "Ring of Fire", and an effective tsunami warning system has long been in place there. Although the extreme western edge of the Ring of Fire extends into the Indian Ocean (the point where this earthquake struck), no warning system exists in that ocean. Tsunamis there are relatively rare despite earthquakes being relatively frequent in Indonesia. The last major tsunami was caused by the Krakatoa eruption of 1883. It should be noted that not every earthquake produces large tsunamis; on 28 March 2005, a magnitude 8.7 earthquake hit roughly the same area of the Indian Ocean but did not result in a major tsunami.
The first warning sign of a possible tsunami is the earthquake itself. However, tsunamis can strike thousands of kilometres away where the earthquake is only felt weakly or not at all. Also, in the minutes preceding a tsunami strike, the sea often recedes temporarily from the coast. This was observed on the eastern side of the rupture zone of the earthquake such as around the coastlines of Aceh province, Phuket island and Khao Lak area in Thailand, Penang island of Malaysia and the Andaman and Nicobar islands. Around the Indian Ocean, this rare sight reportedly induced people, especially children, to visit the coast to investigate and collect stranded fish on as much as 2.5 km (1.6 mi) of exposed beach, with fatal results. However, not all tsunamis cause this "disappearing sea" effect. In some cases, there are no warning signs at all: the sea will suddenly swell without retreating, surprising many people and giving them little time to flee.
One of the few coastal areas to evacuate ahead of the tsunami was on the Indonesian island of Simeulue, very close to the epicentre. Island folklore recounted an earthquake and tsunami in 1907, and the islanders fled to inland hills after the initial shaking and before the tsunami struck. These tales and oral folklore from previous generations may have helped the survival of the inhabitants. On Maikhao beach in northern Phuket, Thailand, a 10-year-old British tourist named Tilly Smith had studied tsunami in geography at school and recognised the warning signs of the receding ocean and frothing bubbles. She and her parents warned others on the beach, which was evacuated safely. John Chroston, a biology teacher from Scotland, also recognised the signs at Kamala Bay north of Phuket, taking a busload of vacationers and locals to safety on higher ground.
Anthropologists had initially expected the aboriginal population of the Andaman Islands to be badly affected by the tsunami and even feared the already depopulated Onge tribe could have been wiped out. Many of the aboriginal tribes evacuated and suffered fewer casualties. Oral traditions developed from previous earthquakes helped the aboriginal tribes escape the tsunami. For example, the folklore of the Onges talks of "huge shaking of ground followed by high wall of water". Almost all of the Onge people seemed to have survived the tsunami.
The tsunami first struck the west and north coasts of northern Sumatra, Indonesia particularly in Aceh province, early in the morning. The largest slip of 30 m (100 ft) was estimated on the subfault located off the west coast of Aceh province. The observed subsidences were 0.2–0.6 m (0.7–2 ft) at Banda Aceh, more than 0.2 m (0.7 ft) at Peukan Bada, and more than 1.5 m (5 ft) at Lhoknga and Leupung.
According to local eyewitnesses at Ulee Lheue in Banda Aceh, the first tsunami reached shore 15–20 minutes after the earthquake, the time interval between the first and second tsunamis was 15–20 minutes, and the second was bigger than the first. The eyewitness report that the second was bigger than the first is the same as that in Khao Lak and Phuket Island in southern Thailand. A local resident at Banda Aceh states that the giant wave was 'higher than my house'. Another resident living 2 km (1.2 mi) near the coast on the outskirt of the city informed that the tsunami was 'like a wall, very black' in colour and had a 'distinct sound' getting louder as it nears the coast.
The maximum height of the tsunami was measured at Leupung, located on the west coast of the northern tip of Sumatra, near Banda Aceh, and reached more than 30 m (100 ft). Roughly speaking, tsunami heights on other coasts were 15–30 m (49 ft-98 ft) on the west coast, 6–12 m (19.7 ft-39.4 ft) on the Banda Aceh coast, about 6 m (19.7 ft) on the Krueng Raya coast – where 3 oil tanks floated out – and about 5 m (16.4 ft) on the Sigli coast. The tsunami heights in Weh Island were 3–6 m (9.8 ft-19.7 ft) on the north coast directly facing the tsunami source and about 3 m (9.8 ft) on the opposite side of the coast. The tsunami height on the Banda Aceh coast is lower than half of that on the west coast. Even within the Banda Aceh coast, the tsunami height reduced by half from 12 m (39.4 ft) at Ulee Lheue to 6 m (19.7 ft) a further 8 km (4.97 miles) to the northeast. One of the reasons seems to be that there is an archipelago between Lhoknga and Banda Aceh. The tsunami advanced about 4 km (2.49 miles) inland at Banda Aceh. Within 2–3 km (1.24-1.86 miles) from the shoreline, houses, except for strongly-built reinforced concrete ones with brick walls, which seemed to have been partially damaged by the earthquake before the tsunami attack, were completely swept away or destroyed by the tsunami.
In Lhoknga, a town within the district of the same name, in Aceh Besar Regency, Aceh Special Region, Indonesia, located on the western side of the island of Sumatra, 13 km (8.08 miles) southwest of Banda Aceh was completely flattened and destroyed by the 2004 Boxing Day Tsunami, where its population dwindled from 7,500 to 400. Tsunami runups following eyewitness accounts of waves were recorded being 35 m (114.8 ft) in height (waves hitting land at the height of 35 m), the highest known tsunami wave known to date. The sea near Lampuuk beach receded before the first wave hit and it had a characteristic cobra-like surfing wave shape and that the last wave 'towers over the highest coconut trees' and was 'like a mountain'. Consequently, the tsunami also stranded cargo ships and barges and destroyed a cement factory near the Lampuuk coast.
Such high and fast waves arising from the epicentre by a megathrust earthquake were later found to be due to splay faults, secondary faults arising due to cracking of the sea floor to jut upwards in seconds, causing waves' speed and height to increase. Moreover, surveyed areas by scientists show runup heights over 20 m (65.6 ft) on the northwest coast of Sumatra in the Aceh province with a maximum runup of 51 m (167.3 ft).
Other towns on Aceh's west coast hit by the disaster included Leupung, Lamno, Patek, Calang, Teunom, Meulaboh and the island of Simeulue. Affected or destroyed towns on the region's north and east coast were Pidie Regency, Samalanga and Lhokseumawe.
The intensity of shaking was recorded at VI-VII on the MSK intensity scale, the major islands affected by the tsunami were in the South, Middle, and North Andaman Islands. The tsunami arrived in the Andaman and Nicobar Islands between 40 and 50 minutes after the earthquake, and it caused extensive devastation to the islands' environment.
Eyewitnesses at Port Blair recall that the water receded before the first wave, and the third wave was the tallest and caused the most damage. However, persons at Hut Bay, Malacca and Campbell Bay — locations far south of Port Blair — reported that the water level rose by about 1–2 m (3.3 ft-6.6 ft) from the normal sea level and remained there before the first wave crashed ashore. Eyewitness reports put the tallest of the waves at about 8 m (26.2 ft) high at Campbell Bay (in Great Nicobar Island), about 10–12 m (32.8 ft-39.4 ft) high at Malacca (in Car Nicobar Island) and at Hut Bay (in Little Andaman Island), and about 3 m (9.8 ft) high at Port Blair (in South Andaman Island). The significant shielding of Port Blair and Campbell Bay by steep mountainous outcrops may have contributed to the relatively low wave heights at these locations, whereas the open terrain along the eastern coast at Malacca and Hut Bay likely contributed to the great height of the tsunami waves 
The tsunami first arrived on the eastern coast and subsequently refracted around the southern point of Sri Lanka (Dondra Head). The refracted tsunami waves inundated the southwestern part of Sri Lanka after some of its energy has been reflected from impact with the Maldives. Sri Lanka is located 1,700 km (1056.33 miles) far from the epicenter and the tsunami source, so no one felt the ground shake and the tsunami hit the entire coastline of Sri Lanka around 2 hours after the earthquake.
The first tsunami waves had initially caused a small flood (positive wave) as it struck the Sri Lankan coastline. Moments later, the ocean floor was exposed to as much as 1 km (0.62 miles) in places due to drawback (negative wave). This was followed by a massive second tsunami wave, which is in the form of a flood. The largest run-up measured was at 12.5 m (41 ft) and greatest inundation distance of 390 m (0.242 miles) in Yala. In Hambantota, tsunami run-ups are measured at 11 m (36.1 ft), a wave height of 8.71 m (28.6 ft) was recorded at Nonagama and tsunami run-up measurements along the Sri Lankan coasts are at 2.4–11 m (7.87 ft-36.1 ft).
The arrival time of the tsunami at Kalmunai area was reported as 8:30 a.m. Sri Lankan Time (3:00 GMT), Hambantota at 8:45 a.m. (3:15 GMT), and Galle port at 9:25 a.m. (3:55 GMT) respectively. In other districts, the arrival time of the first tsunami was estimated by eyewitnesses to be 9:30 a.m. in the Moratuwa district and 9:45 a.m. in the Kahawa and the Beruwala districts. The earthquake occurred at 6:58 a.m. Sri Lankan time, so that the tsunami reached the west coast of Sri Lanka one and a half hours later. However, the second or third tsunami waves were reported to be the largest in many places; for instance, the testified arrival time was 10:30 a.m. in the Kahawa and 11:05 a.m. in the Moratuwa district.
The Sumudra Devi, a passenger train out of Colombo, was derailed and overturned by the tsunami. The tsunami caused the 2004 Sri Lanka tsunami-rail disaster which took at least 1,700 lives, making it the largest single rail disaster in world history by death toll. Estimates based on the state of the shoreline and a high-water mark on a nearby building place the tsunami 7.5–9 m (24.6 ft to 29.5 ft) above sea level and 2–3 m (6.6 ft to 9.8 ft) higher than the top of the train.
In Sri Lanka, the civilian casualties were second only to those in Indonesia. Reports vary on the number of deaths since many people are still missing and the country lacks adequate communications. As of March 1, 2005, estimates state that 36,603 people perished in the months following the tsunami. Another 800,000 people living on the coasts of Sri Lanka have been directly affected. The eastern shores of Sri Lanka faced the hardest impact since they were facing the epicenter of the earthquake. The southwestern shores were hit later, but the death toll was just as severe. The southwestern shores are a hotspot for tourists as well as the fishing economy. Tourism and fishing industries created high population densities along the coast.
The coastal lifestyle of people and degradation of the natural environment in Sri Lanka contributed to the high death tolls. In addition to the high number of fatalities, approximately 90,000 buildings were destroyed. Houses were easily destroyed since they were built mostly from wood.
The tsunami hit the southwest coast of southern Thailand, which was about 500 km (310.69 miles) from the epicenter. The fact that the area has world-famous resorts like in Phuket Island and the tsunami hit the coasts at around high tide, it was a dreadful tragedy. Approximately 5,400 people were killed and 3,100 people are reported missing in Thailand. The places where the tsunami attacked were Khao Lak, Phuket Island, the Phi Phi Islands, Koh Racha Yai, Koh Lanta Yai and Ao Nang of Krabi province, and offshore islands like the Surin islands and the Similan islands, with the most devastated being Khao Lak and Phuket island. The tsunami heights were 6–10 m (19.7 ft-32.8 ft) in Khao Lak, 3–6 m (9.84 ft-19.7 ft) along the west coast, 3 m (9.84 ft) along the south coast, 2 m (6.6 ft) along the east coast of Phi Phi Island and 4–6 m (13.12 ft-19.7 ft) on the Phi Phi Islands.
The largest tsunami in Thailand hit Khao Lak. Some tsunami heights were higher than 10 m (32.8 ft) and the inundated depths were 4–7 m (13.12 ft-23 ft) in the south of Khao Lak. Surveys conducted show that the tsunami inundated the third floor of a resort hotel. The tsunami heights in Khao Lak were much higher than Phuket Island. The reason for this difference seems to have been caused by the local bathymetry off Khao Lak. According to some interviews with local residents and affected tourists, the leading wave produced an initial depression, called a tsunami drawback or 'disappearing sea' effect and the second wave was largest.
On Patong Beach on the west coast – the most popular tourist place in Phuket – the tsunami heights were 5–6 m (16.4 ft-19.7 ft) and the inundated depth was about 2 m (6.6 ft). The tsunami heights became lower from the west coast, the south coast to the east coast of the island. On Karon beach on the west coast, the coastal road was built higher than the shore and it acted as a seawall, protecting a hotel which was behind it. At the southern end of Karon beach, the road was not raised and hotels were damaged. On the east coast of Phuket Island, which was not facing the tsunami source, the tsunami height was about 2 m (6.6 ft). In one river mouth, many boats were damaged. Fortunately, concrete bridge piers were not damaged. The tsunami propagated anticlockwise around Phuket Island, as was the case at Okushiri Island in the 1993 Hokkaido earthquake. According to some interviews with the people, the leading wave produced an initial depression and the second wave was the largest.
The Phi Phi Islands are a group of islands that were affected by the tsunami. The north bay of Phi Phi Don Island opens to the northwest, thus it faced in the direction that the tsunami came from. The measured tsunami height on this beach was 5.8 m (19.02 ft). According to some eyewitnesses accounts, the tsunami came from the north and south, and totally washed the central area away. The ground level here was about 2 m (6.6 ft) above sea level, but there were many cottages and hotels. Therefore, the tsunami waves from the north and south destroyed the area, the south bay opens to the southeast. It faces in the opposite direction to which the tsunami was propagated. Further, Phi Phi Le Island shields the port of Phi Phi Don Island. The measured tsunami height, however, was 4.6 m (15.1 ft) in this port. It indicated that the tsunami propagated around the islands.
The maximum calculated tsunami height on Phuket Island is about 6 m (19.7 ft) and similar to the measured height. On Khao Lak, the maximum calculated height is about 8 m (26.2 ft), and the measured height was a little larger, which ranges from 9–10 m (29.5 ft-32.8 ft).
The tsunami arrived in the states of Andhra Pradesh and Tamil Nadu along the southeast coast of the Indian mainland shortly after 9:00 a.m. At least two hours later, it arrived in the state of Kerala along the southwest coast. Tamil Nadu and Kerala were extensively damaged, while Andhra Pradesh sustained moderate damage. On the southeast coast it was at 9:05 a.m. at Visakhapatnam, 9:05 a.m. at Kakinada, 9:05 a.m. at Chennai, and 9:37 a.m. at Tuticorin; on the southwest coast it was at 11:10 am at Kochi and 12:25 pm at Marmagoa. There were two to five waves of varying amplitude. The water receded after the first wave struck.
The tsunami run-up was only 1.6 m (5.2 ft) in areas in the state of Tamil Nadu that were shielded by the island of Sri Lanka, but was 4–5 m (13.1 ft-16.4 ft) in coastal districts such as Nagapattinam in Tamil Nadu that were directly across from Sumatra. On the western coast, the runup elevations were 4.5 m (14.8 ft) at Kanyakumari District in Tamil Nadu, and 3.4 m (11.2 ft) each at Kollam and Ernakulam Districts in Kerala. Some of these amplitudes are based on eyewitness accounts and may be subjective. The time lapse between the waves also varied from about 15 minutes to about 90 minutes.
The maximum inundation distance varied between 100–500 m (0.062 miles-0.311 miles) in most areas, except at river mouths, where it was more than 1 km (0.62 miles). The inundation distance varied with topology and vegetation. Areas with dense coconut groves or mangroves had much smaller inundation distances, and those with river mouths or backwaters saw much larger inundation distances. The Kerala coast and some of Tamil Nadu coast have seawalls located 100–600 m (0.062 miles-0.373 miles) from the shoreline, and these helped to reduce the impact of the waves. However, when the seawalls were made of loose stones, the stones were carried inland 20–30 m (0.0124 miles-0.0186 miles). Tide levels did not return to normal until after December 29.
The tsunami of 26 December 2004 severely affected the Maldives at a distance of 2,500 km (1553.4 miles) from the epicenter of the magnitude 9.0 earthquake. The Maldives provides an opportunity to assess the impact of a tsunami on coral atolls. The significantly lower tsunami impact on the Maldives compared to Sri Lanka is largely due to the topography and bathymetry of the atoll chain. Reports indicate more than 82 people confirmed dead, with an additional 26 missing and presumed dead, and over 12,000 people homeless. Some 4,000 houses were damaged. In the tourism sector, the country’s largest foreign income earner, out of the 87 resorts, 19 were severely damaged and had to be closed down, while 14 others have suffered major partial damages. Agricultural crops were swept away and most parts of the agricultural land are covered with salty mud leaving it unusable. The flow depths above sea level only reached up to 4 m (13.1 ft) on Vilufushi Island on Thaa atoll.
Other deaths attributed to the tsunami occurred in Malaysia, mainly on the northern states such as Kedah, Perak, Selangor and Penang and on offshore islands such as Langkawi island. Peninsular Malaysia was shielded by the power of the tsunami due to the protection offered by the island of Sumatra, which lies just off the western coast. The death toll stands at 68 in Malaysia.
In Myanmar, the tsunami caused about 90 deaths. Though the country's western Andaman Sea coastline lies at the proximity of the rupture zone, there were fewer deaths here compared to Thailand due to combined geographical and political factors. Bangladesh, located on the northern Bay of Bengal escaped major damage and deaths because the water displaced by the strike-slip fault was relatively little on the northern section of the rupture zone. In Yemen, the tsunami killed 2 people with a maximum runup of 2 m (6.6 ft).
The tsunami's immense power was detected as far away as Africa, specifically on the eastern and southern coasts that faces the Indian Ocean. Countries that were majorly affected with deaths include South Africa (the furthest) - 2, Somalia - 298, Kenya - 1, The Seychelles - 3 and Tanzania - 10.
According to the U.S. Geological Survey a total of 227,898 people died (see table below for details). Measured in lives lost, this is one of the ten worst earthquakes in recorded history, as well as the single worst tsunami in history. Indonesia was the worst affected area, with most death toll estimates at around 170,000. However, another report by Siti Fadilah Supari, the Indonesian Minister of Health at the time, estimated the death total to be as high as 220,000 in Indonesia alone, giving a total of 280,000 fatalities.
The tsunami caused serious damage and deaths as far as the east coast of Africa, with the farthest recorded death due to the tsunami occurring at Rooi Els in South Africa, 8,000 km (5,000 mi) away from the epicentre. In total, eight people in South Africa died due to abnormally high sea levels and waves.
Relief agencies reported that one-third of the dead appeared to be children. This was a result of the high proportion of children in the populations of many of the affected regions and because children were the least able to resist being overcome by the surging waters. Oxfam went on to report that as many as four times more women than men were killed in some regions because they were waiting on the beach for the fishermen to return and looking after their children in the houses.
In addition to the large number of local residents, up to 9,000 foreign tourists (mostly Europeans) enjoying the peak holiday travel season were among the dead or missing, especially people from the Nordic countries. The European nation hardest hit may have been Sweden, whose death toll was 543.
States of emergency were declared in Sri Lanka, Indonesia, and the Maldives. The United Nations estimated at the outset that the relief operation would be the costliest in human history. Then-UN Secretary-General Kofi Annan stated that reconstruction would probably take between five and ten years. Governments and non-governmental organisations feared that the final death toll might double as a result of diseases, prompting a massive humanitarian response. In the end, this fear did not materialise.
For purposes of establishing timelines of local events, the time zones of affected areas are: UTC+3: (Kenya, Madagascar, Somalia, Tanzania); UTC+4: (Mauritius, Réunion, Seychelles); UTC+5: (Maldives); UTC+5:30: (India, Sri Lanka); UTC+6: (Bangladesh); UTC+6:30: (Cocos Islands, Myanmar); UTC+7: (Indonesia (western), Thailand); UTC+8: (Malaysia, Singapore). Since the earthquake occurred at 00:58:53 UTC, add the above offsets to find the local time of the earthquake.
1 Includes those reported under 'Confirmed'. If no separate estimates are available, the number in this column is the same as reported under 'Confirmed'.
2 Does not include approximately 19,000 missing people initially declared by Tamil Tiger authorities from regions under their control.
3 Data includes at least 2,464 foreigners.
4 Does not include South African citizens who died outside of South Africa (e.g., tourists in Thailand). For more information on those deaths, see this
The earthquake and resulting tsunami affected many countries in Southeast Asia and beyond, including Indonesia, Sri Lanka, India, Thailand, the Maldives, Somalia, Myanmar, Malaysia, Seychelles and others. Many other countries, especially Australia and those in Europe, had large numbers of citizens traveling in the region on holiday. Sweden lost 543 citizens in the disaster, while Germany had 539 identified victims.
The last major tsunami in the Indian Ocean was about A.D. 1400. In 2008, a team of scientists working on Phra Thong, a barrier island along the hard-hit west coast of Thailand, reported evidence of at least three previous major tsunamis in the preceding 2,800 years, the most recent from about 700 years ago. A second team found similar evidence of previous tsunamis in Aceh, a province at the northern tip of Sumatra; radiocarbon dating of bark fragments in soil below the second sand layer led the scientists to estimate that the most recent predecessor to the 2004 tsunami probably occurred between A.D. 1300 and 1450.
The 2004 earthquake and tsunami combined are the world's deadliest natural disaster since the 1976 Tangshan earthquake. This earthquake was the third most powerful earthquake recorded since 1900. The deadliest known earthquake in history occurred in 1556 in Shaanxi, China, with an estimated death toll of 830,000, though figures from this period may not be as reliable.
The 2004 tsunami is the deadliest in recorded history. Prior to 2004, the tsunami created in both Indian and Pacific Ocean waters by the 1883 eruption of Krakatoa, thought to have resulted in anywhere from 36,000 to 120,000 deaths, had probably been the deadliest in the region. In 1782 about 40,000 people are thought to have been killed by a tsunami (or a cyclone) in the South China Sea. The most deadly tsunami prior to 2004 was Italy's 1908 Messina earthquake on the Mediterranean Sea where the earthquake and tsunami killed about 123,000.
A great deal of humanitarian aid was needed because of widespread damage of the infrastructure, shortages of food and water, and economic damage. Epidemics were of special concern due to the high population density and tropical climate of the affected areas. The main concern of humanitarian and government agencies was to provide sanitation facilities and fresh drinking water to contain the spread of diseases such as cholera, diphtheria, dysentery, typhoid and hepatitis A and B.
There was also a great concern that the death toll could increase as disease and hunger spread. However, because of the initial quick response, this was minimized.
In the days following the tsunami, significant effort was spent in burying bodies hurriedly due to fear of disease spreading. However, the public health risks may have been exaggerated, and therefore this may not have been the best way to allocate resources. The World Food Programme provided food aid to more than 1.3 million people affected by the tsunami.
Nations all over the world provided over US$14 billion in aid for damaged regions, with the governments of Australia pledging US$819.9 million (including a US$760.6-million aid package for Indonesia), Germany offering US$660 million, Japan offering US$500 million, Canada offering US$343 million, Norway and the Netherlands offering both US$183 million, the United States offering US$35 million initially (increased to US$350 million), and the World Bank offering US$250 million. Also Italy offered US$95 million, increased later to US$113 million of which US$42 million was donated by the population using the SMS system According to USAID, the US has pledged additional funds in long-term U.S. support to help the tsunami victims rebuild their lives. On 9 February 2005, President Bush asked Congress to increase the U.S. commitment to a total of US$950 million. Officials estimated that billions of dollars would be needed. Bush also asked his father, former President George H. W. Bush, and former President Bill Clinton to lead a U.S. effort to provide private aid to the tsunami victims.
In mid-March the Asian Development Bank reported that over US$4 billion in aid promised by governments was behind schedule. Sri Lanka reported that it had received no foreign government aid, while foreign individuals had been generous. Many charities were given considerable donations from the public. For example, in the United Kingdom the public donated roughly £330,000,000 sterling (nearly US$600,000,000). This considerably outweighed the donation by the government and came to an average of about £5.50 (US$10) donated by every citizen.
In August 2006, fifteen local aid staff working on post-tsunami rebuilding were found executed in northeast Sri Lanka after heavy fighting, the main umbrella body for aid agencies in the country said. There had been reports and rumors that the local aid workers had been killed.
The level of damage to the economy resulting from the tsunami depends on the scale examined. While local economies were devastated, the overall impact to the national economies was minor. The two main occupations affected by the tsunami were fishing and tourism. The impact on coastal fishing communities and the people living there, some of the poorest in the region, has been devastating with high losses of income earners as well as boats and fishing gear. In Sri Lanka artisanal fishery, where the use of fish baskets, fishing traps, and spears are commonly used, is an important source of fish for local markets; industrial fishery is the major economic activity, providing direct employment to about 250,000 people. In recent years the fishery industry has emerged as a dynamic export-oriented sector, generating substantial foreign exchange earnings. Preliminary estimates indicate that 66% of the fishing fleet and industrial infrastructure in coastal regions have been destroyed by the wave surges, which will have adverse economic effects both at local and national levels.
While the tsunami destroyed many of the boats vital to Sri Lanka's fishing industry, it also created demand for fiberglass reinforced plastic catamarans in boatyards of Tamil Nadu. Since over 51,000 vessels were lost to the tsunami, the industry boomed. However, the huge demand has led to lower quality in the process, and some important materials were sacrificed to cut prices for those who were impoverished by the tsunami.
But some economists believe that damage to the affected national economies will be minor because losses in the tourism and fishing industries are a relatively small percentage of the GDP. However, others caution that damage to infrastructure is an overriding factor. In some areas drinking water supplies and farm fields may have been contaminated for years by salt water from the ocean. Even though only coastal regions were directly affected by the waters of the tsunami, the indirect effects have spread to inland provinces as well. Since the media coverage of the event was so extensive, many tourists cancelled vacations and trips to that part of the world, even though their travel destinations may not have been affected. This ripple effect could especially be felt in the inland provinces of Thailand, such as Krabi, which acted like a starting point for many other tourist destinations in Thailand.
Both the earthquake and the tsunami may have affected shipping in the Malacca Straits, which separate Malaysia and the Indonesian island of Sumatra, by changing the depth of the seabed and by disturbing navigational buoys and old shipwrecks. In one area of the Strait, water depths were previously up to 4,000 feet (1,200 m), and are now only 100 feet (30 m) in some areas, making shipping impossible and dangerous. These problems also made the delivery of relief aid more challenging. Compiling new navigational charts may take months or years. However, officials hope that piracy in the region will drop off as a result of the tsunami.
Countries in the region appealed to tourists to return, pointing out that most tourist infrastructure is undamaged. However, tourists were reluctant to do so for psychological reasons. Even beach resorts in parts of Thailand which were completely untouched by the tsunami were hit by cancellations.
Beyond the heavy toll on human lives, the Indian Ocean earthquake has caused an enormous environmental impact that will affect the region for many years to come. It has been reported that severe damage has been inflicted on ecosystems such as mangroves, coral reefs, forests, coastal wetlands, vegetation, sand dunes and rock formations, animal and plant biodiversity and groundwater. In addition, the spread of solid and liquid waste and industrial chemicals, water pollution and the destruction of sewage collectors and treatment plants threaten the environment even further, in untold ways. The environmental impact will take a long time and significant resources to assess.
According to specialists, the main effect is being caused by poisoning of the freshwater supplies and of the soil by saltwater infiltration and a deposit of a salt layer over arable land. It has been reported that in the Maldives, 16 to 17 coral reef atolls that were overcome by sea waves are completely without fresh water and could be rendered uninhabitable for decades. Uncountable wells that served communities were invaded by sea, sand, and earth; and aquifers were invaded through porous rock. Salted-over soil becomes sterile, and it is difficult and costly to restore for agriculture. It also causes the death of plants and important soil micro-organisms. Thousands of rice, mango, and banana plantations in Sri Lanka were destroyed almost entirely and will take years to recover. On the island's east coast, the tsunami contaminated wells on which many villagers relied for drinking water. The Colombo-based International Water Management Institute monitored the effects of saltwater and concluded that the wells recovered to pre-tsunami drinking water quality one and a half years after the event. IWMI developed protocols for cleaning wells contaminated by saltwater; these were subsequently officially endorsed by the World Health Organization as part of its series of Emergency Guidelines.
The United Nations Environment Programme (UNEP) is working with governments of the region in order to determine the severity of the ecological impact and how to address it.[needs update] UNEP has decided to earmark a US$1,000,000 emergency fund and to establish a Task Force to respond to requests for technical assistance from countries affected by the tsunami. In response to a request from the Maldivian Government, the Australian Government sent ecological experts to help restore marine environments and coral reefs—the lifeblood of Maldivian tourism. Much of the ecological expertise has been rendered from work with the Great Barrier Reef, in Australia's northeastern waters.
Many health professionals and aid workers have reported widespread psychological trauma associated with the tsunami. Traditional beliefs in many of the affected regions state that a relative of the family must bury the body of the dead, and in many cases, no body remained to be buried. Women in Aceh required a special approach from foreign aid agencies, and continue to have unique needs.
The hardest hit area, Aceh, is considered to be a religiously conservative Islamic society and has had no tourism nor any Western presence in recent years due to armed conflict between the Indonesian military and Acehnese separatists. Some believe that the tsunami was divine punishment for lay Muslims shirking their daily prayers and/or following a materialistic lifestyle. Others have said that Allah was angry that there were Muslims killing other Muslims in an ongoing conflict. Saudi cleric Muhammad Al-Munajjid attributed it to divine retribution against non-Muslim vacationers "who used to sprawl all over the beaches and in pubs overflowing with wine" during Christmas break.
The widespread devastation caused by the tsunami led the main rebel group GAM to declare a cease-fire on 28 December 2004 followed by the Indonesian government, and the two groups resumed long-stalled peace talks, which resulted in a peace agreement signed 15 August 2005. The agreement explicitly cites the tsunami as a justification.
In a poll conducted in 27 countries by GlobeScan for BBC World Service, 15 percent of respondents named the tsunami the most significant event of the year. Only the Iraq War was named by as many respondents. The extensive international media coverage of the tsunami, and the role of mass media and journalists in reconstruction, were discussed by editors of newspapers and broadcast media in tsunami-affected areas, in special video-conferences set up by the Asia Pacific Journalism Centre.
26 December 2004 Asian Tsunami left both the people and government of India in a state of heightened alert. On 30 December 2004, four days after the tsunami, the Portland, Oregon-based company Terra Research notified the India government that its sensors indicated there was a possibility of 7.9 to 8.1 magnitude tectonic shift in the next 12 hours between Sumatra and New Zealand. In response, the India Home Affairs minister announced that a fresh onslaught of deadly tidal waves were likely along the India southern coast and Andaman and Nicobar Islands, even as there was no sign of turbulence in the region. The announcement generated panic in the Indian Ocean region and caused thousands to flee their homes, which resulted in jammed roads. The announcement was a false alarm and the Home Affairs minister withdrew their announcement. On further investigation, the India government learned that the consulting company Terra Research was run from the home of a self-described earthquake forecaster who had no telephone listing and maintained a website where he sold copies of his detection system. Three days after the announcement, Indian National Congress president Sonia Gandhi called Science & Technology minister Kapil Sibal to express her concern about Sibal's 30 December public warning being "hogwash".
The tsunami had a severe humanitarian and political impact in Sweden. The hardest hit country outside Asia, 543 Swedish tourists, mainly in Thailand, died. With no single incident having killed more Swedish people since the battle of Poltava in 1709, the cabinet of Göran Persson was heavily criticized for lack of action.
Smith Dharmasaroja, a meteorologist who predicted the tsunami before it hit, was assigned the development of the Thai tsunami warning system. The Indian Ocean Tsunami warning system was formed in early 2005 immediately after the tragedy of 26 December 2004 to provide an early warning of tsunamis for inhabitants around the Indian Ocean coasts.
The changes in the distribution of masses inside the Earth due to the seism had several consequences. It displaced the North Pole by 2.5 cm. It also changed slightly the shape of the Earth, more specifically it decreased Earth's oblateness by about one part in 10 billion, consequentially increasing Earth's rotation a little and thus shortening the length of the day by 2.68 microseconds.
A missioner in Ranong, a town on the border between Thailand and Myanmar, says locals talk about 600 victims. Burmese political dissidents say the same.
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