Small tsunami hits eastern Australia
This is a transcript of PM broadcast on the ABC at 1800 AEST on local radio.
PM - Friday, June 29, 2001 6:53
JOHN LOMBARD: Last Sunday morning, Bill
Mitchell from the National Tidal Facility in Adelaide had a fright. He received a phone
call that a massive earthquake off Peru might send a Tsunami, or tidal wave, speeding
across the Pacific Ocean.
Well, a day later that wave did hit Australia's East Coast. Luckily it wasn't very big.
Estimates range from 10 centimetres to a metre, but nevertheless it was the most
significant Tsunami to strike Eastern Australia in 40 years.
Ian Townsend reports.
IAN TOWNSEND: As far as earthquakes go it was a big one - 8.2 on the Richter scale. An
earthquake that size in South America sends a Tsunami warning around the Pacific Rim and
when Deputy Director of the National Tidal Facility at Flinders University, Bill Mitchell,
received the call on his mobile phone at nine on Sunday morning, he rushed into work.
The facility has monitoring stations in the Eastern Pacific and he spent several hours
watching them to see if they moved. They did. Luckily, only a third of a metre.
BILL MITCHELL: The waves reached Arpea in Samoa 15-and-a-half hours after the event and
then proceeded on to Vanuatu and then to Australia.
IAN TOWNSEND: How fast would it be travelling?
BILL MITCHELL: Well in the deep ocean, which is on average about four kilometres deep,
they travel at around about 720 kilometres an hour, or it's a bit more than the speed of a
jet aeroplane.
IAN TOWNSEND: What threat do South American earthquakes, though, pose to the East Coast of
Australia? Is there a threat there from a destructive Tsunami?
BILL MITCHELL: Oh, I think with some of these extremely big Tsunamis, big earthquakes such
as what happened in '64, we'd want to be fairly careful about our shipping.
IAN TOWNSEND: The records of tide and wave gauges along the East Australian coast are
still coming in, but the gauge at Roslyn Bay near Bundaberg in Queensland rose 10
centimetres. It's not much, but it is the largest Tsunami to hit the Eastern Coast since
the Chilean earthquake in the early '60s tore boats from moorings in Sydney Harbour.
Senior Technical Officer with the Quake Centre at Queensland University, Col Lyneham, says
some wave-rider boys off Sydney appeared to move a metre around the same time.
COL LYNEHAM: If you were floating around 30, 40 kilometres off shore, you probably
wouldn't notice anything. But if you were say washing down your boat on your slipway
somewhere fronting the ocean down there Sydney, Wollongong, you probably would have had a
swell that suddenly came up and up to your knees and went back again.
Well obviously no-one's reported a wave breaching but maybe if you're a surfer riding out
the front there on the Heads you might have had the ride of your life.
IAN TOWNSEND: The danger, of course, is that one day an earthquake in the Pacific could
cause a larger, more destructive Tsunami to hit the East Coast.
Bill Mitchell from the Tidal Facility says this week's events shows the warning system
does work.
BILL MITCHELL: That's what we're ultimately aiming to look for and gee, if I see it one
day I'll probably have a few palpitations, I would think, and then get my message out.
Hopefully the Emergency Management of Australia would sort of look after the people once
the warnings are issued.
We have, say, in this particular instance an earthquake - a very large earthquake - of the
order of the size that only three of these size occur a year. It generated waves of the
order of 10 centimetres on the East Coast so the problems associated with those Chilean or
Peruvian earthquakes are very small, really, and I wouldn't want to say alarm any
residents living along the shoreline in Eastern Australia.
We have looked at the threat and the East Coast of Australia is of concern only in very,
very extreme rare instances.
In the event of a very large one we would have sufficient warning anyway. You know, it
would be quite a few hours. In this particular instance it was 27-and-a-half hours before
it reached Roslyn Bay from the time of the event. So a lot of warning systems are in place
to feed into Australia in that event.
END OF REPORT
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