With a magnitude of between 9.1 and 9.3, it is the second largest earthquake ever recorded on a seismograph. This earthquake 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 cm (0.4 in) and triggered other earthquakes as far away as Alaska.
The disaster is known by the scientific community as the great Sumatra-Andaman earthquake,and is also known as the Asian Tsunami and the Boxing Day Tsunami. The tsunami occurred exactly one year after the 2003 Bam earthquake and exactly two years before the 2006 Hengchun earthquake.
The plight of the many affected people and countries prompted a widespread humanitarian response. In all, the worldwide community donated more than $7 billion (2004 US dollars) in humanitarian aid.
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 yet before the tsunami struck.On Maikhao beach in northern Phuket, Thailand, a 10-year-old British tourist named Tilly Smith had studied tsunami in geography class 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.
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. Women in Aceh required a special approach from foreign aid agencies, and continue to have unique needs.
The 2004 earthquake and tsunami combined have been described as the deadliest natural disaster since either the 1976 Tangshan earthquake or the 1970 Bhola cyclone, or could conceivably exceed both of these. Because of uncertainty over death tolls, it might never be known for sure which of these natural disasters was the deadliest.