Melburnians were struck by mysterious tremors on Wednesday morning. For seismologists, however, they were the unmistakable shakes of an earthquake.
Although no serious injuries were reported and building damage was relatively minor, the 5.9 magnitude event was a reminder that Australia is still prone to seismic activity.
Adam Pascale, chief scientist at the Melbourne-based Seismology Research Centre, told The New Daily it was the “largest earthquake in Victoria, onshore, in recorded history”.
“So it’s unusual, certainly, and significant.”
But while it was a significant tremor and aftershocks are anticipated, there’s no need to worry about a massive earthquake in the near future.
How common are earthquakes in Australia?
Mr Pascale said it was wrong to assume that Australia is a place where earthquakes don’t happen.
The 1989 Newcastle earthquake might be embedded in the public’s memory as an exception to the rule, but seismic activity is actually happening all the time.
“We put out a weekly map showing usually 30 to 40 earthquakes every week,” he said.
“They’re usually small and people don’t notice them, but occasionally there’s a big one like this that everyone feels.”
Dr Januka Attanayake, the research lead for earthquake seismology at the University of Melbourne, told TND that tremors of Wednesday’s magnitude do occur in Australia, it’s just that they usually happen in remote corners in the north-west.
“The thing is, earthquakes can occur wherever,” he said.
“It doesn’t have to be on tectonic plate boundaries; it’s just that there’s a higher frequency on these boundaries.”
That’s not to mention offshore earthquakes, which are also common but far less noticeable for everyday Australians.
What sort of aftershocks can Victorians expect?
Emergency Management Commissioner Andrew Crisp said there is a risk of aftershocks continuing for “weeks, even months”.
Aftershocks are hard to predict, but experts say we should nevertheless expect them.
“We can get a clue from the 2012 event,” Dr Attanayake told TND, referring to the Gippsland quake that was smaller than the Wednesday morning tremor.
“We had a few seismometers operating around that epicentre, and we recorded aftershocks down to about 40 days.”
Although aftershocks will generally get smaller and smaller, some of them in the coming days will still be noticeable to ordinary people.
Dr Attanayake’s team has installed seismometers near the epicentre to monitor any future activity.
Could something like this happen again?
Earthquakes are unpredictable, but the one certainty is there will be another one.
“Potentially, a magnitude 6 onshore earthquake occurs every several hundred years in this part of the country,” Dr Attanayake said from Melbourne.
Mr Pascale added: “Australia can have a magnitude 7.5 earthquake – there is a potential for it.”
“When and where, we just can’t say, unfortunately.”
He pointed to mountain formations such as the Dandenongs and the Great Dividing Range as evidence of huge seismic activity in the distant past.
What should I do when an earthquake strikes?
In the event of an earthquake, the Victorian State Emergency Service recommends dropping to the ground and, if possible, taking cover under a nearby desk or table.
If you’re in bed, stay put.
“We are asking people to know what to do: Drop, cover and hold [is the] key message when it comes to earthquakes,” Victoria SES chief officer Tim Wiebusch said on Wednesday afternoon.
It’s important to stay away from windows or mirrors, as well as any shelves from which objects could fall.
The Victorian SES also notes that it’s a bad idea to go outside while an earthquake is still happening.
“Research has shown that most injuries occur when people inside buildings attempt to move to a different location inside the building or try to leave,” the SES says on its website.
However, if you are already outdoors, keep clear of buildings and trees until the tremor has passed.
Can I do anything to help?
Federal agency Geoscience Australia has called on people to lodge what is known as a ‘Felt Report’ if they felt the tremors.
This takes into account your approximate location, building type, what you were doing at the time, and other factors to help alert emergency services about the extent of the damage.
More than 30,000 people made such reports in the hours after the earthquake hit Melbourne.
Can we prepare for the future?
You never know when an earthquake might hit, but taking certain precautions like bolting tall furniture to walls is one way to lessen the risk.
Although Australia’s building code mandates that structures must be able to withstand high g-force ground movements, Dr Attanayake said older buildings that might not be up to modern standards are most at risk during earthquakes.
He said you only need to look at the damage done on Melbourne’s Chapel Street to understand what could happen to older buildings.
What about pets?
If your pet was freaked out by Wednesday’s tremors, you are not alone.
“Animals may be startled by earthquakes, and as a result they may vocalise or may hide or seek safety through escape behaviours,” said Dr Anne Quain, from the University of Sydney School of Veterinary Science.
Given they can often separate pets and owners, these incidents are a reminder of the importance of keeping microchips up to date.
Dr Quain also said that – despite persistent urban myths – there is no evidence to suggest animals can predict earthquakes.