2004 Indian Ocean Tsunami: The Boxing Day Disaster Explained

The 2004 Indian Ocean tsunami was a series of giant waves set off by a magnitude 9.1-9.3 earthquake off the coast of Sumatra, Indonesia, on the morning of 26 December 2004. The waves struck the coasts of a dozen countries around the Indian Ocean within minutes to hours, killing about 230,000 people and displacing some 1.7 million. Known in Europe as the Boxing Day tsunami, it was one of the deadliest natural disasters in recorded history and led to the creation of a tsunami warning system for the Indian Ocean.

Background

Off the west coast of Sumatra, the India plate slides beneath the Burma microplate along a great fault called the Sunda megathrust, at a rate of a few centimetres a year. Where the plates stick, strain builds up over centuries until it is released in a large earthquake. Big earthquakes had struck the region before, but scientists did not generally expect a rupture as long as the one that occurred in 2004.

Unlike the Pacific Ocean, where tsunami warning systems had operated since the mid-20th century, the Indian Ocean had no system of deep-ocean sensors or agreed warning procedures. Destructive tsunamis there were rare in living memory, and most coastal communities had no idea of the danger.

The earthquake

At 7:58 a.m. local time (00:58 UTC) on 26 December 2004, the seabed began to rupture about 160 kilometres off the west coast of Aceh province, at a depth of about 30 kilometres. The rupture tore northwards for roughly 1,300 to 1,600 kilometres, past the Nicobar and Andaman Islands, and lasted around eight to ten minutes, the longest duration ever recorded for an earthquake.

With a magnitude estimated at 9.1 to 9.3, it was the third-largest earthquake recorded by seismographs, after the Valdivia earthquake of 1960 in Chile and the Alaska earthquake of 1964. The seabed along the fault was lifted by several metres, pushing up a vast volume of water and sending waves racing across the ocean at the speed of a jet airliner in deep water.

In the open ocean the waves were less than a metre high and passed almost unnoticed beneath ships. As they reached shallower coastal water they slowed down and grew much taller, and arrived not as a single breaker but as a series of surges, often separated by tens of minutes. In many places the second or third wave was the most destructive. The earthquake was so powerful that it set the whole planet vibrating by a centimetre or so and slightly changed the shape of the Earth, and it was followed by hundreds of aftershocks.

The tsunami strikes

Aceh, Indonesia. The waves reached the northern tip of Sumatra within about 15 to 30 minutes. In places the water ran up to heights of 30 metres or more, and it swept several kilometres inland, destroying almost everything in its path. Much of the provincial capital, Banda Aceh, and many towns along the west coast, such as Meulaboh, were devastated. Indonesia suffered about three-quarters of all deaths.

Thailand. About two hours after the earthquake, waves struck the Andaman Sea coast of Thailand, including the beach resorts of Phuket, Khao Lak and the Phi Phi islands, crowded with holidaymakers for Christmas. Around half of the roughly 8,000 dead and missing in Thailand were foreign tourists.

Sri Lanka and India. The waves crossed the Bay of Bengal in about two hours, devastating the eastern and southern coasts of Sri Lanka and the coast of Tamil Nadu in India, as well as the Andaman and Nicobar Islands. In Sri Lanka, a crowded passenger train known as the Queen of the Sea was overwhelmed near the village of Peraliya, killing an estimated 1,700 or more people in the deadliest railway disaster in history.

Further afield. The Maldives, whose islands lie barely above sea level, were flooded. About seven hours after the earthquake the waves reached Somalia, where about 300 people died, and smaller waves were recorded as far away as South Africa and Antarctica.

On many coasts, the first sign of danger was the sea suddenly drawing back, exposing the seabed. Not knowing what this meant, some people walked out to look, and were caught when the waves returned.

The human cost

Exact figures will never be known, because many bodies were never found and some records were lost. The most commonly cited total is about 227,000 to 230,000 dead and missing in 14 countries. The dead included large numbers of children, who were less able to escape or survive the water, and women, who in many places were at home or on the shore waiting for fishing boats.

Thousands of foreign tourists from more than 40 countries also died, mostly in Thailand and Sri Lanka. Sweden and Germany each lost more than 500 citizens, making the tsunami one of the worst natural disasters in their modern history.

The survivors faced enormous losses. Some 1.7 million people were displaced, and hundreds of thousands lost their homes. Fishing communities lost boats, nets and harbours; farmland was poisoned by salt water; and roads, bridges, schools and hospitals were swept away. In Aceh alone, the tsunami destroyed or damaged well over 100,000 homes and killed a large share of the province’s civil servants, teachers and health workers, crippling local government at the moment it was most needed.

By the numbers

Figures are rounded from government and United Nations estimates and differ between sources.

Relief and recovery

The disaster prompted one of the largest humanitarian responses in history. Governments, international organisations and the public worldwide pledged more than 14 billion US dollars, and private donations broke records in many countries. Armed forces from the United States, Australia, India, Singapore and other nations delivered supplies by helicopter and ship. The UN’s emergency relief coordinator, Jan Egeland, played a central role in organising aid, and the former US president Bill Clinton served as UN Special Envoy for Tsunami Recovery from 2005.

The relief effort was later criticised for poor coordination, competition between aid agencies and, in some places, rebuilding that ignored local needs. Even so, epidemics that many feared in the weeks after the disaster did not materialise on a large scale, and over the following years hundreds of thousands of houses were rebuilt. Indonesia set up a special Agency for the Rehabilitation and Reconstruction of Aceh and Nias, which oversaw the rebuilding until 2009.

In Sri Lanka, the tsunami struck areas on both sides of the long civil war between the government and the Tamil Tigers. Hopes that shared suffering would bring the two sides together faded after a plan to share aid was challenged in court in 2005, and the war resumed in earnest the following year.

In Aceh, where Indonesian forces had been fighting the separatist Free Aceh Movement (GAM) for nearly 30 years, the catastrophe gave fresh urgency to peace talks. On 15 August 2005, the Indonesian government of President Susilo Bambang Yudhoyono and GAM signed a peace agreement in Helsinki, ending the conflict.

Myths and facts

It is often claimed that animals sensed the tsunami and fled to safety. There were anecdotal reports of animals moving inland, but no reliable evidence that they detected the waves in a way that could form a warning system.

A better-documented story is that of Simeulue, an Indonesian island very close to the epicentre. Its inhabitants had passed down, through stories and songs, the memory of a tsunami in 1907, which they called smong. When the ground shook, most fled to high ground, and only a handful of people died out of a population of tens of thousands. The case is now widely cited as an example of the value of local knowledge.

Legacy

Under the coordination of UNESCO’s Intergovernmental Oceanographic Commission, Indian Ocean countries built the Indian Ocean Tsunami Warning and Mitigation System, with seismic stations, deep-ocean pressure sensors, sea-level gauges and national warning centres. An interim service began in 2006 and the full system became operational in 2011. Evacuation routes, signs and drills were introduced along many coasts.

The tsunami also transformed public awareness of the danger worldwide. Amateur video from beaches showed millions of people what a tsunami looks like, and the lesson that a sudden retreat of the sea means immediate danger became widely known. The 2011 Tōhoku earthquake and tsunami in Japan, a country with advanced warning systems, showed that even the best preparations cannot remove all risk.

Timeline

• 2004, 26 December, 7:58 a.m. (Sumatra time): A magnitude 9.1-9.3 earthquake ruptures the seabed off Aceh.
• 2004, 26 December, about 8:15-8:30 a.m.: Tsunami waves strike the coast of Aceh, devastating Banda Aceh.
• 2004, 26 December, about 2 hours after the quake: Waves strike Thailand, Sri Lanka and India.
• 2004, 26 December, about 7 hours after the quake: Waves reach the coast of Somalia.
• 2005, 6 January: World leaders meet in Jakarta for a summit on tsunami relief.
• 2005, 28 March: A magnitude 8.6 earthquake strikes near the island of Nias, off Sumatra.
• 2005, 15 August: The Indonesian government and the Free Aceh Movement sign a peace agreement in Helsinki.
• 2006: An interim tsunami warning service for the Indian Ocean begins operating.
• 2011: The Indian Ocean Tsunami Warning and Mitigation System becomes fully operational.

Why it matters

The 2004 tsunami was a disaster on a global scale, killing people from dozens of nations along the shores of an entire ocean. It showed the deadly cost of having no warning system, prompted an unprecedented outpouring of international aid, helped bring peace to Aceh, and changed how the world prepares for tsunamis.