Tsunamis Tsunamis

The risk that tsunami pose to Tasmania is a subject that has had very little research input and no planning response until recently, as a result of the awareness of the devastating consequences that this phenomenon can cause following the Boxing Day 2004 tsunami.

As a direct result of this tsunami the Australian Government funded Geoscience Australia and the Bureau of Meteorology to undertake tsunami modelling from the most likely sources of tsunami, the subduction zones at the margins of the Indo-Australian tectonic plate. Other tsunami forming processes such as volcanic eruptions and large submarine landslides have not been considered at this stage. The first phase of modelling has considered each subduction zone in turn and the results of this study suggest that for Tasmania the tsunami wave amplitudes would be greatest in the southeast. This would be generated from a large earthquake event at the Puysegur Trench (south of New Zealand).

A preliminary shallow water wave modelling study, using the deep water models described above as inputs, has been undertaken to determine the potential areas of inundation and likelihood of tsunamis impacting on southeast Tasmania. This study was largely funded through the Natural Disaster Mitigation Programme.

Preliminary results using the worst case scenarios indicate that considerable inundation could occur in low-lying coastal communities, with the amount of inundation reducing as the waves travel and attenuate up the River Derwent. This hypothesis is based on a number of assumptions and limitations and given the implications for emergency management further supporting information is required.

Palaeotsunami studies have been conducted to determine if Tasmania has experienced tsunamis in the past. One aspect of this research is the analysis of sediment cores to identify sediment deposits related to tsunami events during the last 10 000 years. Mineral Resources Tasmania has also produced a report compiling historical accounts of tsunami or unusual wave events affecting the Tasmanian coast. In order to further this study, MRT seeks information from the general public on any other historical accounts of large or unusual waves impacting on the Tasmanian coastline.

These studies and further research will enable a better understanding of the risk posed by tsunami to Tasmania and lead to the development of appropriate mitigation strategies.

Core sample extracted from coastal swamp, palaeotsunami investigation, Hobart area.

Core sample extracted from coastal swamp, palaeotsunami investigation, Hobart area.