When is an earthquake not an earthquake? Answer, when it’s a tsunami. Of course that’s just wordplay, because the Sumatra-Andaman earthquake is virtually unknown while the whole world has heard of the Indian Ocean tsunami of 2004. The latter was, of course, a consequence of the former – an undersea megathrust quake that occurred off the west coast of Sumatra. A moment magnitude of 9.3 made this the second most powerful earthquake ever recorded, and the consequences were catastrophic.
The resultant tsunami destroyed the nearby Indonesian town of Lhoknga before roaring off to inundate coastlines all-round the Indian Ocean. In deep water the fast-moving tsunami barely rose above normal sea level, but as it approached land – and shallow water – it slowed and formed waves as tall as 30 m (100 ft). These developed unstoppable momentum capable of reaching inland for 2 km (1.24 mi) in places.
Although the tsunami hit Indonesia immediately, it took seven hours to arrive at the furthest point where it had significant impact: Somalia. Even so, there was no warning system and over 200,000 people, including thousands of tourists, were killed before this fearsome natural phenomenon was spent. Around a third of the casualties were children, who found it harder to survive the rushing waters than adults, while more women than men perished. This was because the menfolk of numerous fishing villages were at sea and rode out the wave while the women waited on shore for their return.
Deaths were recorded in 14 countries, and those who suffered the greatest number of fatalities were Indonesia, Sri Lanka, India and Thailand. A massive international response ensured that ample aid was offered, but as always delivery was patchy and it was predicted that many shattered communities would take a decade or more to rebuild.
When: December 26 2004
Where: Indian Ocean
Death toll: A precise figure was impossible to compute, but reliable estimates suggest around 230,000 people died, including 9,000 foreign tourists who had decided to travel to the welcoming Indian Ocean for a relaxing Christmas holiday.
You should know: The power of the Indian Ocean tsunami was calculated as being equivalent to five megatons of TNT – or to put it another way, more than twice the destructive force of all the munitions used in the whole of world war II, including the two atom bombs dropped on Japan.