How the 2004 Indian Ocean earthquake transformed tsunami science Premium

20th anniversary of the 2004 Indian Ocean tsunami, highlighting lessons learned, advancements in research, and future risks.

December 26, 2024, marks the 20th year since the 2004 Indian Ocean earthquake and tsunami. The tsunami generated by the quake of magnitude 9.1 was sourced off the Sumatran coast and was the third largest (by magnitude) in the world since 1900. The source was 30 km below the ocean floor, in the Sunda trench, where part of the Indo-Australian plate subducts beneath the Burma microplate, which is a part of the Eurasian plate.

The 2004 earthquake ripped through 1,300 km of the plate boundary, the fault tearing from Sumatra in the south to Coco Islands in the north. The quake was felt in Indonesia, Bangladesh, India, Malaysia, the Maldives, Myanmar, Singapore, Sri Lanka, and Thailand. It caused severe damage and killed hundreds in Northern Sumatra and in the Andaman and Nicobar Islands. The tsunami was most impactful on distant shores, affecting 17 countries lining the Indian Ocean.

In all, with an astounding death toll of around 227,000 plus 1.7 million more displaced, the 2004 tsunami is the deadliest in recorded history.

In less than six years, on March 11, 2011, a magnitude 9.1 earthquake hit the east coast of Japan, the largest ever recorded in that country. It generated a tsunami that reached as high as 39 metres and travelled up to 8 km inland. The twin disasters killed more than 18,000 people, displaced more than 500,000, and resulted in the Fukushima Daiichi nuclear power plant accident.

Although devastating tsunamis have occurred in the past — 1960 Chile and 1964 Alaska, for example — the two 21st century events taught us important lessons. Particularly, the 2004 tsunami highlighted how vulnerable the world was to natural hazards. It landed like a bolt from the sky, hitting the most unexpected locations, and placed a premium on the importance of tackling disaster risk through preparedness and resilience.

As Margareta Wahlström, head of the UN Office for Disaster Risk Reduction (UNISDR), observed in a panel discussion: “Ten years after the Indian Ocean tsunami, the world has taken significant measures to make the world a safer place against disasters.”

The 2004 tsunami surprised researchers and hazard managers alike with its transoceanic reach. With no recorded history of any event of such magnitude, the research community hadn’t anticipated it occurring along India’s eastern seaboard. The only previous tsunamis had occurred in 1881, caused by a large earthquake (magnitude ~8) off Car Nicobar island, and another in 1883 due to the explosion of Krakatoa. These events produced only small sea surges as recorded by tide gauges at different points on the east coast.