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Tsunamis in Australia?

Tristan Meyers, Saturday August 1, 2015 - 15:37 AEST

With another earthquake of 5.7 magnitude being recorded today near off the southern Queensland coast, meteorologists and oceanographers are keeping a wary eye on the potential for tsunamis. Thankfully, these earthquakes that have been occurring have not generated any significant tsunamis.

Tsunamis are large waves that are generally associated with tectonic uplift, although a large meteor may also have enough energy to produce a tsunami. When an earthquake occurs, it can change the depth of the seabed. Water is heavy - a cubic metre of it weighs about one tonne! A tsunami's energy derives from this quick adjustment in depth of the seabed, which can be great enough to shift the several kilometres of water that may lay overhead.

In order for a tsunami to become a significant risk to Australia, an earthquake must be "tsunamigenic". This means it is generally of magnitude of 6.5 or greater and occurring at depth of 100 km or less near the coast.

Contrary to what most people believe, Australia is at risk from tsunamis. Unfortunately, information Australia's past relationship with tsunamis is difficult to come by, since it is often locked within the geology of a large region. Such evidence can present itself as rapid and substantial erosion, large boulders in strange locations, or a large area of uniform, but unusual sediments (tsunami deposits).

However, a large earthquake in the notoriously geologically active pacific could generate a tsunami that may reach Australia. As recent as 2011, a tsunami hit the eastern Australian coast, originating from Japan. However, by the time it reached the shore, it had petered out to just a 35 cm wave, recorded at Port Kembela.

- Weatherzone

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