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The 2004 Indian Ocean earthquake was an undersea earthquake that occurred at 00:58:53 UTC (07:58:53 local time) on December 26, 2004. The earthquake generated tsunamis that were among the deadliest disasters in modern history. At a magnitude of 9.0, it was the largest earthquake since the 9.2 magnitude Good Friday Earthquake off Alaska in 1964, and tied for fourth largest since 1900.

The earthquake originated in the Indian Ocean just north of Simeulue island, off the western coast of northern Sumatra, Indonesia. The resulting tsunamis devastated the shores of Indonesia, Sri Lanka, India, Thailand, and other countries with waves of up to 15 m (50 feet) high, even reaching the east coast of Africa, 4500 km (2,800 miles) west of the epicenter.

At least 150,000 people are known to have died as a result of the tsunamis and the count is still taking place. The true final toll may never be known due to bodies swept out to sea, but it is likely to be higher than the current estimate. Relief agencies warn of the possibility of more deaths to come as a result of epidemics because of poor sanitation, but the threat of starvation seems now to have been averted [1]. The plight of the many affected people and countries prompted a widespread humanitarian response.

Animation of the tsunami caused by the earthquake. (See also the full-length version)

Note: Tsunamis have very low height while travelling over deep ocean, and ocean-going vessels in their path do not usually notice them. High waves only occur when shallow water is reached. The shallow water acts as a brake on the bottom part of the wave,thus sending the fast moving water up.

Quake characteristics

The earthquake was initially reported as 6.8 on the Richter scale. The Pacific Tsunami Warning Center(PTWC) also estimated it at 8.5 shortly after the earthquake. On the moment magnitude scale, which is more accurate for quakes of this size [2], the earthquake's magnitude was first reported as 8.1 by the U.S. Geological Survey. After further analysis, this was increased to 8.5, 8.9, and finally to 9.0 [3].

Since 1900, the only earthquakes recorded with a greater magnitude were the 1960 Great Chilean Earthquake (magnitude 9.5), the 1964 Good Friday Earthquake in Prince William Sound (9.2), and the March 9 1957 earthquake [4] in the Andreanof Islands (9.1). The only other recorded earthquake of magnitude 9.0 was in 1952 off the southeast coast of Kamchatka [5]. (See Top 10 earthquakes). Each of these megathrust earthquakes also spawned tsunamis (in the Pacific Ocean), but the death toll from these was significantly lower—a few thousand for the worst one — probably because of the lower population density along the coasts near affected areas and the much greater distances to more populated coasts.

The hypocenter was at 3.316°N, 95.854°E, some 160 km (100 miles) west of Sumatra, at a depth of 30 km (18.6 miles) below mean sea level (initially reported as 10 km). This is at the extreme western end of the Ring of Fire, an earthquake belt that accounts for 81 percent of the world's largest earthquakes [6]. The earthquake itself (apart from the tsunamis) was felt as far away as Bangladesh, India, Malaysia, Myanmar, Thailand, Singapore and the Maldives.

The earthquake was unusually large in geographical extent. An estimated 1200 km (750 miles) of faultline slipped about 15 m (45 ft) along the subduction zone where the India Plate dives under the Burma Plate. The slip did not happen instantaneously but took place in two phases over a period of several minutes. Seismographic data indicates that the first phase involved the formation of a rupture about 400 km long and 100 km wide, located 30km beneath the sea bed. The rupture proceeded at a speed of about 2 km/s, beginning off the coast of Aceh and proceding north-westerly over about 100 seconds. A pause of about another 100 seconds took place before the rupture continued northwards towards the Andaman and Nicobar Islands. [7]

The India Plate is part of the great Indo-Australian Plate, which underlies the Indian Ocean and Bay of Bengal, and is drifting northeast at an average of 6 cm/year (2 inches/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 the Burma Plate which includes the Nicobar Islands, the Andaman Islands and northern Sumatra. The India Plate slips deeper and deeper beneath the Burma Plate until the increasing temperature and pressure turns the subducting edge of the India Plate into magma which eventually pushes the magma above it out through the volcanoes (see Volcanic arc). This process is interrupted by the locking of the plates for several centuries until the build up of stress causes their release resulting in a massive earthquake and tsunami. 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 bed is estimated to have risen by several metres, triggering devastating tsunami waves. The tsunamis did not originate from a point source, as mistakenly depicted in many illustrations of their spread, but radiated outwards along the entire 1200 km length of the rupture. This greatly increased the geographical area over which the waves were observed, reaching as far as Mexico and Chile.

Aftershocks and other earthquakes

Numerous aftershocks were reported off the Andaman Islands, the Nicobar Islands, and the region of the original epicenter in the hours and days that followed. The largest aftershock was 7.1 off the Nicobar Islands [8]. Other aftershocks of up to magnitude 6.6 continue to shake the region on a daily basis [9].

The earthquake came just three days after a magnitude 8.1 earthquake in an uninhabited region west of New Zealand's sub-Antarctic Auckland Islands, and north of Australia's Macquarie Island [10]. This is unusual, since earthquakes of magnitude 8 or more occur only about once per year on average [11]. Some seismologists have speculated about a connection between these two earthquakes, saying that the former one might have been a catalyst to the Indian Ocean earthquake, as the two quakes happened on opposite sides of the Indo-Australian tectonic plate [12]. However the USGS sees no evidence of a causal relationship [13].

Coincidentally, the earthquake struck almost exactly one year (to the hour) after a magnitude 6.6 earthquake killed an estimated 30,000 people in the city of Bam in Iran [14].

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. [15]

Power of the earthquake

The total energy released by the earthquake in the Indian Ocean has been estimated as 2.0 exajoules (2.0×10¹⁸ joules) [16]. This is enough to boil 150 litres (40 US gallons) of water for every person on Earth. It is estimated to have resulted in an oscillation of the Earth's surface of about 20 to 30 cm, equivalent to the effect of the tidal forces caused by the Sun and Moon. [17] The shock waves of the earthquake were felt across the planet - as far away as Oklahoma, vertical movements of 0.12 in (3 mm) were recorded. [18]

The shift of mass and the massive release of energy very slightly altered the Earth's rotation. The exact amount is yet undetermined, but theoretical models suggest the earthquake shortened the length of a day by 2.68 microseconds (2.68 µs) (or about one billionth of the length of a day) [19] 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 inch) [20], [21] or perhaps by up to 5 or 6 cm [22]. However, due to tidal effects of the Moon, the length of a day increases by 15 µs every year, so any rotational speedup due to the earthquake will be quickly lost. Similarly, the natural Chandler wobble of the Earth can be up to 15 m (50 ft).

More spectacularly, some of the smaller islands southwest of Sumatra may have moved southwest up to 20 m (66 ft). The northern tip of Sumatra, which is on the Burma Plate (the southern regions are on the Sunda Plate), may also have moved up to 36 m (118 ft) southwest. Movement was likely both vertical as well as lateral. Measurements using GPS and satellite imagery are being used to determine the extent and nature of actual geophysical change.[23]

Tsunami characteristics

The red color means that the water level is higher than normal, while the blue means lower.See larger version

The shaking of the seabed by the earthquake displaced massive volumes of water, resulting in tsunamis that struck the coasts of the Indian Ocean; the deadliest tsunamis by far in all of recorded history.

See a full-length animation of how the waves travelled — large file (about 1 MB) — to see exactly how and why some countries were more affected than others

According to Tad Murty, vice-president of the Tsunami Society, the total energy of the tsunami waves was 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 [24].

Two radar satellites that happened to be overhead at the right moment recorded two wavefronts 500–850 km apart with a height of 50 cm. These are the first such observations ever made. [25]

Because the 1,200 km of faultline affected by the quake 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.

Coasts that have a land mass between them and the tsunamis' location of origin are usually safe; however, tsunami waves can sometimes diffract around such land masses. Thus, the Indian state of Kerala was hit by tsunamis despite being on the western coast of India, and the western coast of Sri Lanka also suffered substantial impacts. Also, distance alone is no guarantee of safety: Somalia was hit harder than Bangladesh despite being much farther away.

Due to the distances involved, the tsunamis took anywhere from fifteen minutes to seven hours (for Somalia) to reach the various coastlines (see travel time maps: [26] ). 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 two hours later. Thailand was also struck about two hours later, despite being closer to the epicenter, because the tsunami travelled more slowly in the shallow Andaman Sea off its western coast.

Damage and casualties

File:2004 tsunami banda aceh shoreline before & after june 23 2004 satellite.jpg

Banda Aceh Shoreline Before & After Comparison. Notice that in the after shot, most of the shoreline has been completely submerged. Picture credit: DigitalGlobe

The death toll from the earthquake, the tsunamis and the resultant floods totals to over 150,000 people with tens of thousands reported missing, and over a million 6000000 were left homeless. Early news reports after the earthquake spoke of a toll only in the "hundreds", but the numbers rose steadily reparing over the following week.

Relief agencies report that one-third of the dead appear to be children. This is a result of the high proportion of children in the populations of many of the affected regions and the fact that children were the least able to resist being overcome by the surging waters.

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, especially Scandinavians. The European nation hardest hit may have been Sweden [27].

States of emergency were declared in Sri Lanka, Indonesia and Maldives. The United Nations has declared that the current relief operation will be the costliest ever. UN Secretary-General Kofi Annan has stated that reconstruction would probably take between five and ten years. Governments and NGOs fear the final death toll may double as a result of diseases, prompting a massive humanitarian response.

Measured in lives lost, this is one of the ten worst earthquakes in history([28]). It is also the single worst tsunami in history; the previous record was the 1703 tsunami at Awa, Japan that killed over 100,000 people ([29]).

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); UTC+6: (Bangladesh, Sri Lanka); UTC+6:30: (Cocos Islands, Myanmar); UTC+7: (Indonesia (western), Thailand); UTC+8: (Malaysia, Singapore). Since the quake occurred at 00:58:53 UTC, add the above offsets to find the local time of the quake. A list of times can be found at a USGS site.

Template:2004 Indian Ocean earthquake casualties

Countries affected

File:Sumatra devastation1.jpg

A village near the coast of Sumatra lies in ruin.

Main article: Countries affected by the 2004 Indian Ocean earthquake

The earthquakes and resulting tsunamis affected a large number of countries in Southeast Asia and beyond, including Indonesia, Sri Lanka, India, Thailand, the Maldives, Somalia, Myanmar, Malaysia and others. Many other countries, especially in Europe, had large numbers of citizens travelling in the region on holiday.

Casualties in historical context

The earthquake was the fourth most powerful recorded since 1900, and the confirmed death toll so far is 150,000, in large part due to the ensuing tsunami. The deadliest earthquakes since 1900 were the Tangshan, China earthquake of 1976, in which at least 255,000 were killed, the earthquake of 1927 in Xining, Qinghai, China (200,000), the Great Kanto earthquake which struck Tokyo in 1923 (143,000), and the Gansu, China earthquake of 1920 (200,000). The deadliest known earthquake in history occurred in 1556 in Shaanxi, China, with an estimated death toll of 830,000, though figures from this time period may not be reliable ([30]).

This 2004 tsunami is the deadliest in recorded history. Prior to 2004, the deadliest recorded tsunami was the result of an earthquake near Awa, Japan in 1703 that killed 100,000. Forty-thousand people were killed in 1782 by a tsunami in the South China Sea, and the tsunami created by the 1883 eruption of Krakatoa is thought to have resulted in 36,000 deaths. The most deadly tsunami between 1900 and 2004 occurred in Messina, Italy on the Mediterranean Sea where the earthquake and tsunami killed 70,000 in 1908. The most deadly tsunami in the Atlantic Ocean resulted from the 1755 Lisbon earthquake that, combined with the toll from the actual earthquake and resulting fires, killed over 100,000.

The 2004 earthquake and tsunamis seems to be the worst natural disaster since the 1970 Bhola cyclone (Bangladesh), estimated to have killed 500,000.

Signs and warnings

Malé, the capital island of Maldives was severely hit.

Despite a lag of up to several hours between the earthquake and the impact of the tsunamis, nearly all of the victims were taken completely by surprise. This is because there is no tsunami warning system in the Indian Ocean to detect tsunamis, and equally importantly, warn the general populace living around the ocean quickly. Tsunami detection is not easy because while a tsunami is in deep water it has a very low 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. [31]

Scientists were also hampered by the fact that the initial estimate for the magnitude of the earthquake was 8.1. The determination that the earthquake had actually been much stronger (and the resulting tsunami much larger) was not made until after the tsunamis had already struck.

Tsunamis usually occur in the Pacific Ocean due to 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 due to the rarity of tsunamis there — the last major one was caused by the Krakatoa eruption of 1883.

In the aftermath of the disaster there is a new awareness of the need for a tsunami warning system for the Indian Ocean. The UN aims to have a working East Asia and Southeast Asia early warning system within a year [32]. Some have even proposed creating a unified global tsunami warning system, to include the Atlantic Ocean and Caribbean.

See also the 2004 Indian Ocean tsunami timeline, a minute to minute account by the National Oceanic and Atmospheric Administration (NOAA).

Unfamiliarity with warning signs

The first warning sign of a possible tsunami is the earthquake itself; however tsunamis can strike thousands of miles 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. People in Pacific regions are more familiar with tsunamis and often recognize this phenomenon as a sign to head for higher ground. However, 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 of exposed beach, with fatal results. [33]

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 — before the tsunami struck [34]. On Maikhao beach in northern Phuket, Thailand, a 10 year old British girl named Tilly Smith had studied tsunamis in geography class at school and recognised the warning sign of the receding ocean. She and her parents warned others on the beach, which was evacuated safely [35].

Human component in magnitude of damage

An article in the Wall Street Journal on December 31, 2004 commented that human destruction of coral reefs that had formerly protected some coastal areas was a significant factor in the loss of life and damage in the area. The article pointed to the Surin Island chain off Thailand's coast as an example of protection afforded by the still intact reefs of the area. Fewer people perished in the protected areas. Many reefs areas around the Indian Ocean have been dynamited because they are considered impediments to shipping, an important part of the South Asian economy. Other factors have been the removal of coastal dunes and mangrove forests.

Post-tsunami humanitarian situation

Main article: Humanitarian response to the 2004 Indian Ocean earthquake

A great deal of humanitarian aid is needed due to widespread damage of the infrastructure, shortages of food and water, and economic damage. The United Nations suggests that a further 150,000 at extreme risk of disease [36]. Epidemics are of special concern, as they are likely due to the high population density and tropical climate of the affected areas. The overwhelming concern of humanitarian and government agencies is to provide sanitation facilities and fresh drinking water to contain the spread of diseases such as cholera, diphtheria, dysentery and typhoid.

Nations all over the world have so far provided over USD3 billion in aid for damaged regions, with the Australian federal government pledging $US 810 million (including a USD 754 million aid package for Indonesia^[37]), the German government offering USD 660 million, the Japanese government offering USD 500 million, the United States government offering USD 350 million, and the World Bank offering USD 250 million. Officials estimate that billions of dollars will be needed.

On 9 January 2005 a cricket match was held at the Melbourne Cricket Ground, Melbourne, Australia, between an "Asian XI" and a "Rest of the World XI", which raised AUS 14.5 million for disaster relief.

Coastal fishing communities and their fisherfolk, some of the poorest people in the region, have been the most devastated with high loss of life as well as boats and fishing gear [38].

Some economists believe that damage to the affected countries' 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. [39]

In the days after the event, significant effort was spent in burying bodies hurriedly; this may not have been the best way to allocate resources. See Dead bodies and health risks.

The World Food Programme is feeding 2 million people affected by the tsunamis[40].

Environmental impact of the tsunami

Beyond the heavy toll on human lives, the Indian Ocean earthquake has caused an enormous environmental impact which 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.

According to specialists [41], the main effect is being caused by poisoning of the fresh water supplies and the soil by salt water infiltration and deposit of a salt layer over arable land. It has been reported that in the Maldives, 16 to 17 coral reef atols that were overcome by sea waves are totally without fresh water and could be rendered unhabitable 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.

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 them [42]. UNEP has decided also to earmark a US$ 1,000,000 emergency fund and to establish a Task Force with this aim.

External links

Tsunami help

See Donations for victims of the 2004 Indian Ocean earthquake and Humanitarian response to the 2004 Indian Ocean earthquake

Ongoing news collections

ABC News Online – Asian Tsunami Disaster Australia
BBC News – In-Depth Report: Asia Quake Disaster UK
CBC News – Indepth: Disaster in Asia Canada
Channel News Asia – Special Coverage: Killer Waves Singapore
CNN – Special: Tsunami Disaster USA
Guardian Unlimited – Special Report: Indian Ocean Tsunami Disaster UK
Hindustan Times — The Killer Waves India
New York Times – Complete USA
Rediff – Tsunami: Waves of Destruction India
Sydney Morning Herald – Waves of Devastation Australia
Yahoo! News – Asia Tsunami Disaster USA
Guardian's World News Guide for finding local news sources

Scientific reports

Videos

Video of debris flow in Banda Aceh, taken by a wedding photographer and broadcast on Metro TV in Indonesia
Amateur videos posted on a weblog
Tsunami Videos, updated daily
Videos of Phi Phi island (Thailand) before and during the tsunami
Full Tsunami Video Footage, Pictures, Clips And TV News Stories
Raw Footage, organized into weekly releases
5 Amateur Camcorder Videos Torrents of the tsunami as it hit Sri Lanka, Thailand, and Malaysia. Requires Blogtorrent (free, 2.3M).
Video from Patong beach hotel
Video from Sri lanka beach hotel
BBC news report with video coverage
Amateur Asian Tsunami Video Footage

Photos

Gallery of images: satellites ….
Satellite photos with DHTML image comparison.
15 videos of the tsunami amateur videos
Yahoo! Slideshows — Asian Tsunami Disaster
Photos during and after the destruction of Koh Phi Phi Island
Satellite images of tsunami-affected areas (National University of Singapore) Updated on 6th January
Pictures of the Tsunami
Phuket Island, Thailand
Interactive Mapping of Affected Regions
Images :: Tsunami Aftermath — Penang Island, Malaysia life after the tsunami
Images :: Visit to Kota Kuala Muda, Kedah, Malaysia Relief work in the northern state
Tsunami photos at Flickr

Forums and discussion

Sites to help family and friends locate missing loved ones are listed on the "Links to search for missing people" section of the "Countries affected by the 2004 Indian Ocean earthquake" page.

Tsunami Forum Warnings, Surviving A Tsunami, Stories, Missing persons, Frustrations.
Condolence Book Offer your condolences to the victims of the December 26, 2004 Indian Ocean earthquake
Talk about the tsunami in general, express your feelings on the donation situation, or just share your survival story.
A discussion of "What causes Tsunamis" and how those concerned about or working on environmental issues can work to accurately describe the disaster.
Float a Lotus A light hearted place to post thoughts and ease pain of the tragic event.

@@ Line 71: / Line 71: @@
 The [[death toll]] from the earthquake, the tsunamis and the resultant floods totals to over
 <!-- NOTE: The casualty total is derived from the national totals described in the relevant country sections, which are added in the casualty table. Do NOT change the total number below without updating the relevant national information and the casualty table. -->
-,000 people with tens of thousands reported missing, and over a million left homeless. Early news reports after the earthquake spoke of a toll only in the "hundreds", but the numbers rose steadily over the following week.
+,000 people with tens of thousands reported missing, and over a million 6000000 were left homeless. Early news reports after the earthquake spoke of a toll only in the "hundreds", but the numbers rose steadily reparing over the following week.
 Relief agencies report that one-third of the dead appear to be children. This is a result of the high proportion of children in the populations of many of the affected regions and the fact that children were the least able to resist being overcome by the surging waters.