About Tsunami

What is a Tsunami?

Sources of Tsunami (Courtesy Geoscience Australia)Sources of Tsunami (Courtesy Geoscience Australia)A tsunami is a series of waves generated by a number of causes including:
  • Vertical movement of the sea floor as the result of a large earthquake
  • Submarine or coastal volcanic eruptions
  • Meteor impacts 
  • Coastal landslides and slumps, either land-based or submarine

Historical Tsunami in Australia

Australia has been affected by over 50 Tsunami in the past 200 years.

Map of the major earthquake zones that could cause tsunami that impact NSW The largest Tsunami to have affected the NSW coast in recent times occurred in May 1960 after a 9.5 magnitude earthquake in Chile resulted in a 1 metre tidal fluctuation at Fort Denison in Sydney Harbour. This caused widespread damage to marine infrastructure along the NSW Coast including damage to boats, wharves, jetties and beaches.

More information about the May 1960 Tsunami can be found here

More information regarding tsunami can be found at Tsunami: The Ultimate Guide

Where do Tsunami that affect NSW come from?

Most tsunami occur in the Pacific and Indian Oceans. The boundary of the Pacific Ocean experiences frequent earthquakes. This boundary is commonly known as the Ring of Fire. There are two major subduction zones in the Indian Ocean that can also generate tsunami.

Tsunami can be generated by a number of causes including, volcanic eruptions, undersea landslides and meteor impacts. However, undersea earthquakes are the more likely source of tsunami that could affect NSW.

Map of the major earthquake zones that could cause tsunami that impact NSW Earthquakes from subduction zones are the most common source of destructive tsunami. These earthquakes are generated when two tectonic plates meet and one goes under the other, usually at a rate measured in centimetres. The sinking (subducting) plate drags against the upper plate, causing flexing. Continued stress on the plate boundary results in the upper plate rebounding to its original position, displacing the sea water above. This can lead to the generation of tsunami waves.

There is a moderate likelihood of tsunami in NSW compared with other parts of the world. Tsunami do have an effect on our coastline, Even with relatively small tsunami, there could be strong waves, rips and currents and unusual sea levels that can be dangerous.

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