Australia's coast battered by tsunamis
Australia's coastline has felt the impact of almost 50 tsunamis in the past 150 years, according to the first catalogue of all such events.
Dr Dale Dominey-Howes from Macquarie University in Sydney brought together records of these huge ocean waves from a host of different sources in an effort to help improve tsunami protection efforts.
"After the Indian Ocean tsunami of 2004, lots of people have asked what the risk is to Australia of future tsunamis," Dominey-Howes says.
"The first step in answering that question is to gather this kind of information."
He found historical evidence for 47 tsunamis that have affected Australia since 1858 including 44 that have hit the New South Wales coast, 12 in Western Australia, 9 in Queensland, and 10 in Tasmania.
The numbers add up to more than 47 as individual tsunamis can affect the coasts of different states at once.
The most recent tsunami to affect Australia was recorded on 17 July 2006, Dominey-Howes writes in a paper to be published in the journal Marine Geology.
It was caused by an earthquake in Indonesia and affected the tides in Western Australia and South Australia.
Although a large number of tsunamis have been recorded in New South Wales, that's mostly because the state has been densely populated for longer, the researcher says.
"That's where the vast majority were found, but we shouldn't be too surprised. It's probably an artefact of our occupying the New South Wales coast for so long."
Every few years
According to Geoscience Australia, a tsunami is recorded on Australia's coastline roughly once every two years, but most are very small and classified low-risk.
Some, however, have been significant. In August 1977, for example, an Indonesian earthquake caused waves to reach 6 metres above sea level in the north of Western Australia, according to the new report.
Looking further back in time, Dominey-Howes also gathered geological reports of tsunamis. For example, one surge may have hit Jervis Bay in New South Wales some 9000 years ago causing the sea to rise more than 100 metres.
But Dominey-Howes raises a question mark over the evidence for these older so-called mega-tsunamis, which are based on finds of shells, sand and boulders where waves may have left them.
"The problem is that a lot of that work is highly controversial," he says. "I propose that we should treat them with caution."
Meanwhile, the more recent evidence Dominey-Howes has gathered is already being used by the Australian government to help decide where to place tsunami early-warning systems, he says.
"We should be putting some detection equipment toward the northeast of Australia because places like Papua New Guinea and Indonesia are major sources of tsunamis," he says.
"Likewise, there's a definite need to put that equipment in the northwest, between us and Java and Sumatra."