In this explainer sequence, 9news.com.au is analyzing the issues and fears round pure disasters, analyzing potential impacts on Australia.
For hundreds of years, myths and legends have swirled round massive destructives waves which have crashed onshore, claiming lives and destroying houses.
The civilizations on the time believed these waves had been despatched from larger powers, however science now tells us they may have been tsunamis; a Japanese time period comprised of two phrases,”tsu”, which suggests harbour, and “nami”, which suggests “wave”.
Here we break down what we find out about tsunamis, together with the place in Australia they’re most certainly to happen, and the place they’ve hit previously.
The National Oceanic and Atmospheric Administration (NOAA) defines a tsunami as ”a series of waves caused by earthquakes or undersea volcanic eruptions.”
“As the waves travel inland, they build up to higher and higher heights as the depth of the ocean decreases,” it explains.
“The speed of tsunami waves depends on ocean depth rather than the distance from the source of the wave.”
Professor Phil Cummins, a senior seismologist at Geoscience Australia, advised 9news.com.au it is vital to know a tsunami is not only one wave.
Instead he prefers utilizing the analogy of ripples in an ocean.
“I define a tsunami as an ocean disturbance, caused by a rapid displacement of a large body of water,” he stated.
“If you threw a stone into a pond there would be a single disturbance, but there would be many ripples that go through the pond.
“Those ripples, are a part of that disturbance.”
There are two types of tsunamis; local and Far Field, or distant tsunamis, which are generated from a long way away.
What was the largest tsunami in history?
The largest recorded tsunami occurred in a place called Lituya Bay in Alaska on July 9, 1958.
An 8.3 magnitude earthquake occurred along the Fairweather Fault and triggered a debris avalanche.
The rushing fall of rocks and debris created a colossal wall of water measuring more than 500 metres tall.
Five people died in the disaster, but Howard Ulrich, a father who was out fishing with his son, managed to survive.
“They had the anchor out, and he could not pull it in in time,” Cummins said.
“The father turned to his son and advised him to wish, and someway they lived.
“A boat can survive a tsunami, as it can just float over it.”
When was the final tsunami in Australia?
These had been linked to the Tōhoku earthquake in Japan, which triggered harmful tsunami waves as much as 40-metres excessive within the Asian nation.
The results in Australia had been far much less extreme.
A 56 centimetre wave was noticed at Norfolk Island, a 35 centimetre one at Port Kembla in New South Wales, and a 23 centimetre wave at Spring Bay in Tasmania.
“Unusual currents were noted at Port Kembla and Sydney Harbour,” BoM stated.
“(And) several swimmers were washed into a lagoon at Merimbula, NSW”.
Also of notice, is an eight-metre tsunami noticed in Steep Point, Western Australia in 2006.
This occurred after a earthquake in Java, Indonesia.
“That was the largest run-up ever measured in Australia,” Cummins defined.
“The run-up, is the maximum height the wave measured on land.
“It was someplace round seven to eight metres.”
The wave destroyed “a number of campsites” and there was evidence of inundation up to 200 metres inland.
And on May 23, 1960 small tsunami waves were also observed across Queensland, NSW, South Australia, Victoria and Tasmania.
This was linked to an earthquake in Chile.
“It was definitely observable in Sydney Harbour with out devices,” Cummins said.
“I believe it was a few metre on the tide gauge. It tore boats from their moorings and brought about robust currents.”
Post-Christmas heatwave brings back scorching Aussie summer
Where in Australia is a tsunami more likely to occur?
Cummins said there are two areas around the country’s coast deemed most at risk of tsunamis.
“The one which worries me most is the south-east coast, that city space round Sydney,” he said.
“That might probably be affected if there was a big earthquake south of New Zealand, which might additionally have an effect on the jap coast of Tasmania.
“Sydney is more vulnerable, simply because there’s more people, a lot close to the beach, and the density of construction.”
Cummins added that the north-western coast of Australia has skilled probably the most frequent tsunami waves previously, however two elements minimise the affect.
“As it so happens that coast is also affected strongly by tropical cyclones,” Cummins stated.
“First of all there aren’t that many big cities, but secondly, the settlements tend to have moved up the beach a bit to avoid storm surges associated with cyclones.
“So, I do not assume the danger is so excessive on the north-west coast though it does expertise probably the most frequent tsunamis.”
How vulnerable is Australia to tsunamis?
While Australia is at risk of tsunamis, Cummins said the country is in a relatively safe position due to its distance from neighbouring countries and subduction zones, which are where two plates collide.
“The foremost sources are south of New Zealand, as a result of usually it is a subduction zone that causes the very massive thrust earthquakes, which causes very massive tsunamis.
“There’s subduction south of New Zealand and north.”
How lengthy would it not take for a tsunami to hit Australia?
Should the worst case state of affairs happen and a robust earthquake hit off the coast of New Zealand, Cummins stated the mainland would have about two hours warning earlier than the waves began to reach.
“That’s a pretty quick time for it to hit,” he stated, earlier than including some good news.
“But so far we haven’t recorded a really large earthquake, even historically, in those areas.”
The different potential tsunami supply can be South America.
“These days we would be well aware it’s on its way, and a pretty good idea of even the height.
“You’d have a minimum of 12-hours warning. That’s a lot.”
Is there a warning before a tsunami?
The short answer to this is yes, at least in Australia.
Local tsunamis, which are experienced in countries like Japan, Indonesia and New Zealand, can arrive in as up to as little as 30-minutes, but Australia doesn’t face this threat.
Our country is also protected by the “world class” Joint Australian Tsunami Warning Centre (JATWC), which provides 24 hour tsunami monitoring, assessment and warnings.
“For us, one other factor that may be finished is to make use of the GPS satellites,” Cummins explained.
“As it seems a tsunami, though it might solely be a metre or so excessive within the open ocean, disturbs the environment.”
“As that disturbance propagates upwards it will get to be fairly massive and impacts the ionosphere, and that impacts the alerts of the GPS satellites.
“That may be helpful for Australia, as we have more time to deal with it.”
Cummins added earthquakes themselves can function warnings for native tsunamis.
“There are guidelines for numerous nations,” Cummins explained.
“But ‘strong, long, and get gone’, is what New Zealand says.
“If there’s robust shaking that lasts for a very long time, stand up hill.”
