Swansea vulnerable to tsunamis

SWANSEA has been named in a state report as one of the five locations most vulnerable to a tsunami in NSW.

The NSW Office of Environment and Heritage and the NSW State Emergency Service compiled the report.

It named Swansea, Manly, Botany Bay, Wollongong and Merimbula as being "potentially more vulnerable than other locations in NSW to tsunami inundation".

The areas have been selected for further study, with academic models to be prepared to predict tsunami inundation.

The study will be part of a NSW tsunami risk assessment.

A preliminary risk assessment found the NSW coast had a "moderate tsunami hazard level".

"The main contributors to the hazard come from earthquakes on the Vanuatu, Kermadec and Puysegur trenches," it said.

"NSW is exposed to tsunami originating from a range of possible sources, mostly from within a highly active seismic zone known as the Pacific Ring of Fire, which spans 40,000 kilometres, borders four continents and is made up of volcanoes, earthquakes, deep sea trenches and major fault zones."

The report said a tsunami could "devastate coastal regions due to the immense volumes of water and energy involved".

This, it said, was demonstrated in the 2004 Boxing Day tsunami in south Asia, where 230,000 people from 14 countries died and millions more were displaced.

Landslides, volcanic eruptions and meteorite impacts can cause tsunamis, but earthquakes generated 75 per cent of all tsunamis.

"Tsunami waves in the deep ocean usually possess a wavelength of 10 kilometres to 500 kilometres," it said.

"Such waves can travel at speeds up to 800km/h and can cover trans-oceanic distances in hours."

Large tsunamis comprise multiple waves hitting shores over a period of hours, with 10 minutes to 30 minutes between wave crests.

"The first wave to reach the shoreline may not have the highest run up," the report said.

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