The 2004 Boxing Day Tsunami

What caused the 2004 Boxing Day Tsunami and what effect did it have?

The 2004 Indian Ocean earthquake was an undersea megathrust earthquake that occurred on December 26, 2004, with an epicentre off the west coast of Sumatra, Indonesia. The earthquake itself is known by the scientific community as the Sumatra-Andaman earthquake.  With a magnitude of between 9.1 and 9.3, it is the third largest earthquake ever recorded on a seismograph. This earthquake had the longest duration of faulting ever observed, between 8.3 and 10 minutes. It caused the entire planet to vibrate about 1 cm and triggered other earthquakes as far away as Alaska. Its hypocenter was between Simeulue and Banda Aceh, mainland Indonesia, which therefore meant that this conflict-ravaged area was the worst affected.

The tsunami itself was caused due to a massive displacement of water. When the denser Indo-Australian Plate slipped under (subducted) the Eurasian Plate, instead of letting the Indo-Australian plate just subduct, the Eurasian Plate rebounded upwards about 20 metres, which is what caused such a massive displacement of water. This tsunami behaved very much like other tsunamis at first. When it was in deep water it travelled at a fast velocity of 1000km per hour, but slowed down to 10km per hour when in shallow water, creating extremely large destructive waves. Measuring no more than a few centimetres in open water, the tsunamis grew rapidly in height as they approached land. Some of these waves reached heights of 30m.

These tsunamis had utterly disastrous consequences. All of the countries affected were still developing countries, and the coastside buildings were mostly fishermen’s huts, or beach side resorts. This meant that the buildings were neither sturdy, nor prepared for any sort of natural disaster, let alone a tsunami. Tsunamis were not very common in the Indian Ocean, so the coastal communities in these countries were unaware of the threat posed by tsunamis, and therefore totally unable to cope. Many low-lying, flat islands in the Indian Ocean (e.g. The Maldives) had been hit as well, and the fishing and tourist establishments were right at the water’s edge to maximise use of the magnificent beaches. This meant that the tsunami rolled well inland, and even inundated some smaller islands. Perhaps one of the largest causes of the large death scale, is that there is no early tsunami warning system in the Indian Ocean. Only Thailand had one and even that clearly failed to work.

The United Nations has compiled an analysis that states that a total of 229866 people were lost, with 186983 dead, and another 42883 missing. In Myanmar, only 61 people were reported to be dead, but most people think that 400 to 600 people died.