<Tr> <Th> Tsunami </Th> <Td> 15 to 30 metres (50 to 100 ft) with maximum runup of 51 m (167.3 ft) at Lhoknga . </Td> </Tr> <Tr> <Th> Casualties </Th> <Td> 230,000--280,000 dead and more missing </Td> </Tr> <P> The 2004 Indian Ocean earthquake occurred at 00: 58: 53 UTC on 26 December with the epicentre off the west coast of Sumatra, Indonesia . The shock had a moment magnitude of 9.1--9.3 and a maximum Mercalli intensity of IX (Violent). The undersea megathrust earthquake was caused when the Indian Plate was subducted by the Burma Plate and triggered a series of devastating tsunamis along the coasts of most landmasses bordering the Indian Ocean, killing 230,000--280,000 people in 14 countries, and inundating coastal communities with waves up to 30 metres (100 ft) high . It was one of the deadliest natural disasters in recorded history . Indonesia was the hardest - hit country, followed by Sri Lanka, India, and Thailand . </P> <P> It is the third - largest earthquake ever recorded on a seismograph and 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 centimetre (0.4 inches) and triggered other earthquakes as far away as Alaska . Its epicentre was between Simeulue and mainland Indonesia . The plight of the affected people and countries prompted a worldwide humanitarian response . In all, the worldwide community donated more than US $14 billion (2004) in humanitarian aid . The event is known by the scientific community as the Sumatra--Andaman earthquake . The resulting tsunami was given various names, including the 2004 Indian Ocean tsunami, South Asian tsunami, Indonesian tsunami, Christmas tsunami, and the Boxing Day tsunami . </P>

What caused the tsunami in the indian ocean