The 2004 Boxing Day tsunami was the worst natural disaster of its kind in human history.
An earthquake registering a magnitude of at least 9.1 struck off the coast of northern Sumatra, Indonesia, in the Indian Ocean at 7.58am local time on December 26, 2004.
Within 15 minutes, waves began striking the coasts of northern Sumatra and the Nicobar Islands, according to the Australian Institute for Disaster Resilience.
About two hours later, tsunamis reached Sri Lanka, India and Thailand.
And about seven hours later, the waves hit as far as Mauritius and the east coast of Africa.
The US National Oceanic and Atmospheric Administration estimates waves reached 51 metres tall in Indonesia’s Aceh province in Northern Sumatra.
Those waves were about 30 times the size of the average Australian person and seven times the size of a two-storey home.
At least 227,000 people were killed in more than a dozen countries stretching from Indonesia to as far as the coast of Africa, with Indonesia, Sri Lanka, Thailand and India some of the worst hit.
Among the dead were 26 Australians.
The Australian Institute for Disaster Resilience has dubbed it the single worst tsunami in history and one of the 10 worst earthquakes in recorded history.
“It certainly is the biggest tsunami resulting in the most deaths and that goes all the way back to recorded history year 365,” Geoscience Australia’s head of community safety Dr John Dawson said.
“The thing for me that makes it stand out is the number of deaths of people who were killed a long way away from the earthquake.
“There were over 52,000 deaths more than 1000 kilometres from the earthquake and that’s unusual for disasters.”
The magnitude of the earthquake is very rare, Dawson said, adding that the only other one in recent times to reach that scale was in the Tōhoku region of Japan in 2011, which caused the Fukushima nuclear disaster.
“In 2004 there wasn’t an Indian Ocean tsunami warning capability so the region was blind to it and that’s one of the reasons there were so many deaths – the wave arrived without warning,” he said.
“We can’t predict earthquakes but they are part of a process that is recurring on time scales of hundreds of years so we would expect more to come and that’s why we maintain an operational capability to monitor for tsunamis.”
Since the Indian Ocean earthquake, Geoscience Australia and the Bureau of Meteorology have been working together to monitor earthquakes and potential tsunamis.
This year for the 20th anniversary, they’re hoping the event hasn’t strayed too far from our memories.
“That’s the risk with very rare but catastrophic events that it just drifts out of people’s memories and they forget,” Dawson said.
“That’s why it’s also important to reflect on the 2004 event and say this could conceivably happen again.
“Are our communities ready for that?”
