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A study is under way to find if Australia and New Zealand were hit by mega-tsunamis many times the size of the 2004 Boxing Day one and what risk there is of a repeat.
Controversial data suggest three or four huge tsunamis may have hit southeastern Australia during the past 10,000 years, although scientists are divided about how severe they were.
Researchers have pointed to sedimentary evidence and the presence of large boulders deposited on 30m-tall cliffs in the Jervis Bay area of the New South Wales south coast, as well as strange rock formations at Cathedral Rocks, 80km south of Sydney.
If such large events did occur in the region, there should also be geological evidence in New Zealand. So the hunt is on.
Dr Dale Dominey-Howes, from the University of New South Wales, is heading the new three-year study, which aims to establish how real the risk is of a catastrophic tsunami in the future.
Researchers say more than 300,000 lives and property worth more than $176 billion on the New South Wales coast could be vulnerable if a big tsunami hit.
Dr Dominey-Howes is sceptical about some of the tsunami claims, but says the possibility that huge waves had hit Australia must be properly investigated.
"If it is true, it has profound implications for vulnerability and risk on the southeast coast ... it would be really scary."
Dr James Goff, from New Zealand's National Institute of Water and Atmospheric Research, is also part of the new research team.
He says the study, paid for by the Australian Government, is important because it will investigate New Zealand's West Coast as well.
Previous studies have looked at only half of the picture because a huge tsunami should leave behind geological evidence in both countries.
"Are the deposits we see in Australia correct, and are they being interpreted correctly? If so, then where the heck are they in New Zealand?"
He says the study will also seek to find the source of any mega-tsunamis in and around the Tasman. Earthquakes are simply not strong enough to account for the apparent mega-tsunami sediments found in Australia.
AAP
