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Indian Ocean Tsunami Animation

Watch an animation of the 2004 Boxing Day Indian Ocean Tsunami.

tsunami

Download the 4.3 megabyte animation here. It is in *.mov format.
Best played with Apple Quicktime Player.
Modelling performed by William Power using the MOST software developed by Vasily Titov at PMEL.

The Indian Ocean tsunami of 26 December 2004 was generated by a very large earthquake off the coast of Sumatra. At magnitude 9.3, the earthquake was larger than first reported, and the second largest ever recorded by scientific instruments. The earthquake ruptured across an area that extends for 1200 kilometres. This rupturing deformed the seabed, raising a huge volume of water above its normal level, which then spread out as the tsunami.

The tsunami caused huge devastation and in excess of 280,000 deaths in countries bounding the Indian Ocean. By the time it reached New Zealand, the tsunami was measured to be as much as half a metre in height at some locations, despite the great distance between here and the earthquake, and the landmass of Australia in between. How can we explain this?

The speed of tsunami waves is determined by the depth of water in which the tsunami travels. One consequence of this is that the tsunami path is refracted, or bent, by changes in water depth, in much the same way that light is refracted when it passes through a glass lens. At the start of the tsunami most of the wave energy traveled either west towards Sri-Lanka and India, or east towards Thailand. Some of the waves spread out to the south, where wave energy was channeled by a ridge of undersea mountains which extends down to the south of Australia. From here some of the waves traveled east towards the South Pacific.

To the south of New Zealand lies the Campbell Plateau, a large shallow area which is an extension of the New Zealand landmass, and which extends for about a thousand kilometres into the Southern Ocean. When the tsunami waves reached this plateau they slowed, and were refracted north towards the east coast of South Island. This may explain why some of the largest waves from this tsunami in New Zealand were measured in Timaru.

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