Melbourne experienced its strongest earthquake in 120 years on Sunday night, and the aftershocks could go on for years – but an expert told The New Daily the activity is not unusual.
A 3.8 magnitude earthquake hit the Melbourne suburb of Sunbury about 11.40pm on Sunday, with Geoscience Australia reporting tremors were felt as far north as Bendigo and as far south as Hobart.
Chief scientist at the Seismology Research Centre, Adam Pascale, said Australia’s lack of constant, strong earthquakes means the ground is quite solid and unbroken, allowing the energy waves from an earthquake’s epicentre to travel – and be felt – a fair distance away.
Are earthquakes more frequent?
Sunday’s earthquake came less than two years after a 5.9 magnitude earthquake hit Woods Point, Victoria, and was felt interstate, and just two weeks after a 2.3 magnitude quake was felt in the Melbourne suburb of Ferntree Gully.
However, Mr Pascale said not much has changed in recent years.
“The actual rate of the earthquakes that are happening in the region is pretty much within the expectations that we have,” he said.
“We look at an area, we say, ‘How often should we expect the magnitude 4 to occur?’ and this is within that time frame.
“Although it appears that we’re having more earthquakes that are being felt, I think people communicate that information … much more quickly. So something that you might feel, if you put it on social media, you can have that confirmed pretty quickly because other people in the area have felt that.”
Australia has a reputation for being largely earthquake-free, thanks to its relatively central location on the Australian Plate, but the country still sits on the tip of many of the tectonic plate’s fault lines.
Australia sits on top of one of the fastest-moving tectonic plates in the world, with the Australian Plate moving north at “the rate that your fingernails grow”.
It’s that pressure from the boundaries of the plates being pushed that is contributing to the stress within the plate that results in the country’s earthquakes.
This means Australia records at least one magnitude 5 earthquake every year, and a magnitude 6 about every 10 years.
Mr Pascale said there are up to 40 earthquakes per week in south-eastern Australia alone.
Which regions have the most earthquakes?
Regions most prone to seismic activity are those that already have a lot of mountains or hills.
“Wherever you see mountains, you’ve probably got earthquakes creating those mountains over millions of years, so the Great Dividing Range, which starts in Victoria … we tend to get more activity out there,” he said.
“[Also] around Adelaide, the Flinders Ranges; again, more hills [means] more earthquakes over long periods of time.”
Although it’s not yet confirmed which fault Sunday’s quake originated from, there are more than 370 Australian intra-plate faults, fault-related folds and other features relating to earthquakes large enough to deform the Earth’s surface.
More are still being discovered, with a previously unknown ‘blind’ fault revealed in March thought to be behind Victoria’s 2021 earthquake.
Can earthquakes be predicted?
“There’s no way of predicting earthquakes,” Mr Pascale said.
“Stress in the rocks is building up many, many kilometres below the surface, and we can’t monitor that at all. Even if we could, we wouldn’t know what the strength of the rock is before it’s going to break.
“But we can give forecasts of what we expect to happen once an earthquake like this has occurred; like the rate of aftershocks, how long we expect them to go, what the chances of a larger event might be.”
There have been several aftershocks since Sunday’s quake, and these could continue for days, weeks or years – Mr Pascale said there are still ongoing aftershocks following the Woods Point 2021 event.
