Research here at UON aims to support emergency managers like the NSW State Emergency Services (SES) in keeping us safe from the threat of tsunami.
The majority of tsunami are caused by subduction zone earthquakes under the ocean. The underwater trenches where this happens are called source zones. Here in NSW, we are exposed to several source zones in the Pacific Ocean. These are the closest ones:
The Australian Government runs the Joint Australian Tsunami Warning Centre (JATWC), which uses available data and science to issue tsunami warnings to the Australian public. This is run through both Geoscience Australia and the Bureau of Meteorology.
The research we are working on will contribute to the body of knowledge in tsunami science and help to improve the accuracy of tsunami warnings and further our understanding of the tsunami threat.
Predicting a tsunami involves predicting the earthquake that generates it, the nature of the tectonic plate movements that generate the tsunami and then predicting how the tsunami travels across the oceans. The focus of our research here at UON is what happens when the tsunami comes close to land and when it reaches the shore.
We do this by creating a 3D representation of the terrain at a particular location, such as Sydney Harbour. Then we use modelling software to calculate what would happen if a tsunami were to occur. The model also incorporates tides and runs over the course of the entire tsunami. This is important because tsunami aren’t just individual waves but a series of waves that occur over a long period of time. This is often as long as 12 to 24 hours.
The results of our modelling reveal what the experience of a tsunami would look like in a particular location. These results can then be used to plan for a tsunami in the future. If the tsunami wave comes onto land, then evacuation zones can be drawn out. If the results predict particularly high currents, then the port authorities can plan accordingly. A holistic description of the hazard will provide the information that emergency managers need to keep us safe.
The tsunami behaviour we see in the model results helps us to improve our understanding of the science behind tsunami behaviour and also allows us to draw conclusions that may also apply elsewhere.
This example image of a model from Manly in Sydney shows the areas that would expect to be impacted directly by a large tsunami. The inset image shows the direction of water currents midway through the event and illustrates how the flooding is predicted to occur from the ocean side as well as from inside the Harbour . The overall image also shows that North Head, the peninsula in the south of the image, could potentially be isolated if such a tsunami could occur. These are all important factors for the SES to consider when planning for a tsunami event in this location.