The 2004 Indian Ocean Earthquake and Tsunami

On the morning of December 26, 2004, the seafloor off northern Sumatra heaved upward along a fault about 1,300 kilometers long, in shaking that lasted close to ten minutes. The magnitude 9.1 to 9.3 earthquake displaced an immense volume of water and sent tsunami waves across the Indian Ocean. They struck Aceh within about 20 minutes, Thailand and Sri Lanka within two hours, and the coast of Somalia about seven hours later. About 228,000 people died in 14 countries, the deadliest tsunami in recorded history. Most coasts had no warning system, and few people recognized the signs. Because it struck the day after Christmas, tourists from dozens of countries were among the dead, making a regional catastrophe a global one.

The epicenter lay near Simeulue Island, off the west coast of northern Sumatra and about 250 kilometers south-southeast of Banda Aceh, at a depth of about 30 kilometers. It sits on the Sunda megathrust, where the India Plate slides beneath the Burma microplate. The rupture ran north past the Nicobar and Andaman Islands, lifting some coral reefs out of the water and sinking other coasts. In Aceh, waves ran up more than 30 meters in places and swept several kilometers inland, flattening much of Banda Aceh and the town of Meulaboh. Sri Lanka's east and south coasts, the Indian state of Tamil Nadu, the Andaman and Nicobar Islands, and Thailand's Andaman coast around Khao Lak and Phuket were hit hard. The Maldives, Myanmar, Malaysia, Somalia, Kenya and Tanzania also lost lives.

Tolls compiled by national governments and the United Nations total about 228,000, including roughly 167,000 in Indonesia, 35,000 in Sri Lanka, 16,000 in India and 8,000 in Thailand, figures that combine confirmed deaths and people listed as missing. About 1.7 million people were displaced. The disaster prompted one of the largest international relief efforts on record, with about 14 billion US dollars pledged. In Aceh it also helped end a long armed conflict, as the Indonesian government and the Free Aceh Movement signed a peace agreement in Helsinki in August 2005. UNESCO coordinated a new Indian Ocean Tsunami Warning and Mitigation System, fully operational since 2011, and schools across the region now teach that a sudden retreat of the sea is a signal to run for high ground.

• The 2011 Tōhoku Earthquake and Tsunami
  Japan's strongest recorded earthquake, whose tsunami killed nearly 16,000 people and caused the Fukushima Daiichi nuclear accident another great megathrust tsunami
• Indonesia
  The world's largest archipelago, spanning two oceans epicenter off
• Sumatra
  A vast volcanic island anchoring western Indonesia epicenter off
• The Tectonic Plates
  The seven great slabs and dozens of smaller ones that make up Earth's moving shell India–Burma plate boundary
• The Ring of Fire
  The Pacific rim of subduction, where the ground does not hold still on the western end of
• Bay of Bengal
  The world's largest bay and cradle of the deadliest cyclones tsunami crossed
• Indian Ocean
  The world's third-largest and warmest ocean tsunami crossed
• India
  The world's most populous nation and largest democracy tsunami struck
• Maldives
  A scattering of low coral atolls in the Indian Ocean tsunami struck
• Somalia
  The Horn of Africa, where land meets two seas tsunami struck
• Sri Lanka
  A teardrop island of tea, temples, and tropical biodiversity tsunami struck
• Thailand
  The never-colonized kingdom at the heart of mainland Southeast Asia tsunami struck