Frequently Asked Questions
More about Tsunami
Q: What is a Tsunami?
A: A tsunami is a series of travelling waves generated by the sudden displacement of the sea by submarine earthquakes, volcanic eruptions, landslides or asteroid impacts. The word ‘tsunami’ is Japanese for ‘harbour wave’.
Q: Have there been any tsunami that have impacted NSW in the past?
A: At least 44 tsunami have been recorded in NSW since European colonisation. However 4 were noted/observed including some which caused damage to boats and other marine infrastructure, including the 1960 Chilean Tsunami, the 1868 Chilean Tsunami, the 1877 tsunami from North Chile and the tsunami caused by the 1883 eruption of Krakatoa.
Q: How fast are tsunami?
A: Tsunami speed is dependent on water depth. In deeper water and in the open ocean, waves can reach speeds of 900 km per hour, as fast as a jumbo jet. However as a tsunami wave enters shallow water (for example as it approaches the coast), its speed decreases rapidly.
Q: How big will the wave be?
A: Each location will be different; tsunami height at the coast is dependent on the configuration of the coastline, the shape of the ocean floor, reflection of waves, tides and wind waves.
The wave height is also dependant on the source of the tsunami (direction and size). Narrow bays, inlets and estuaries may cause funnelling effects that enhance tsunami wave height. The combination of these factors means that the flooding produced by a tsunami can vary greatly from place to place.
Q: How do I find out about Tsunami Watches and Warning?
A: Tsunami warning products are broadcast by the Joint Australian Tsunami Warning Centre. Given the short lead times, the public (via media channels) receives tsunami warning information at the same time as Emergency Services and other organisations.
Community safety advice will be contained in Tsunami Warning products. This will provide the public with information about what they should do in response to the tsunami threat. The response advice is tailored to the level of the threat (ie Marine and immediate foreshore threat or Land inundation threat). The Joint Australian Tsunami Warning Centre is the authorised information and warning source for tsunami in NSW
Q: What is the likely warning lead time for tsunami?
A: This will depend on what causes the tsunami and where the source of the wave is. As travel times differ, for a tsunami generated by an earthquake in the Puysegur Trench (near New Zealand), the effective warning time could be as little as 90 minutes.
There may be little to no warning time for a tsunami generated by a continental shelf collapse. Here the only warning people would receive would be from natural warning signs such as the earth shaking.
Q: What is the immediate foreshore?
A: The immediate foreshore is low lying land adjacent to the water. This could include beaches, low lying camp grounds, low lying walkways. It is important to realise that tsunami also affect estuaries and coastal lakes.
Q: What do I do if I hear a Tsunami Warning?
A: The general public should follow community safety advice that will be included in the Tsunami Warning Product from the Joint Australian Tsunami Warning Centre. People should act quickly in response to the advice contained in the warning.
Q: How do agencies know what their roles are when they receive a warning?
A: In NSW, agency roles are defined and agreed to in the NSW Tsunami Emergency Sub Plan. The NSW State Emergency Service is the combat agency for tsunami and is responsible for planning and preparing for and responding to an emergency resulting from a tsunami.
For more information, please visitNSW State Emergency Service
Bureau of Meteorology
Joint Australian Tsunami Warning Centre
Australian Emergency Management Knowledge Hub