Earthquake risk: Check our map of Victorian fault lines. Do you live above one?

Victorians may be oblivious to most of them but hundreds of earthquakes rattle the state each year. So are the number of tremors now on the rise?

The magnitude 2.4 earthquake in Pakenham on Wednesday morning is just one of hundreds each year across the state, but most we are oblivious to.

Head of Seismology at The University of Melbourne Dr Januka Attanayake told the Herald Sun while it seemed like there was more earthquake activity in Victoria now than in the past, that was not the case.

Science and technology had just become better at detecting the “many very tiny earthquakes” that occurred regularly, he said.

“We have a seismic record of about 200 years and we don’t see an increase in activity … overall, if you take a time average seismic rate, we are not experiencing more events,” Dr Attanayake said.

“However, because we have put more and more seismometers on the ground, we are recording more and more smaller events. For example, if you look at Gippsland region prior to 2017, we recorded about 150 to 200 events a year but since 2017, the University of Melbourne has developed a pretty sophisticated high seismic network in that area and now we are recording about 450 events a year.”

A 4.6-magnitude earthquake woke some Victorians last Friday, hitting 127km east of Melbourne, near Rawson.

The state was also hit by a record breaking 5.8 magnitude earthquake in September 2021, that caused damage in parts of Melbourne and elsewhere.

Dr Attanayake said scores of fault lines lay below Victoria, with most concentrated in the south west and east of the state, and Bendigo also a hotspot.

And any more fractures in the earth’s crusts — or faults — existed in Victoria than scientists had managed to map.

“We’re still in the process of mapping all the fault lines, it’s an ongoing process,” he said.

“These fractures in the Earth’s crust are progressive, and they exist almost everywhere. It’s just that some of these faults are discovered when an earthquake has occurred, so it’s very difficult to say exactly where these fault lines are but we know that they exist beneath our feet.”

Damaged buildings in Melbourne after a magnitude 6.0 earthquake that was felt across south east Australia in September 2021. Picture: Getty Images

It’s possible Friday morning’s earthquake was an aftershock of the 2021 event that hit Melbourne. Picture: Getty Images

Scientists had managed to map about 80 per cent of Victoria’s fault lines to date, he said.

“But giving a number (of faults) is very difficult because every time there’s an earthquake, a large earthquake, it’s likely that it’s occurred on a pre-existing fault that we haven’t detected yet,” Dr Attanayake said.

“The Australian landmass is one of the oldest landmasses in the world. It’s been pushed pulled, stretched in different directions at different times of its evolution. So obviously, it will have a whole bunch of fractures in its crust.”

In good news for Victoria’s gold detectors, there is truth in their belief that earthquakes increase the chance of the precious metal being found, Dr Attanayake said.

A recent study by Queensland University showed that during earthquakes pressure in a fault line dropped so dramatically “that it could precipitate gold”. It also happened instantly.

Gold detectors have reason to get excited after earthquakes.

But they should only expect minute amounts of gold, rather than nuggets.

But in less good news, it occurred “at very large depths” of up to 10km underground and was likely to produce only very small amounts of gold near the earth’s surface.

“They say that this is an instantaneous process but the downside is it will only precipitate a minute amount of gold that’s not worth mining. You have to have thousands of earthquakes, over thousands of years, for it to be worthy of mining,” Dr Attanayake said.

“But I can understand why the gold mining community or the people who are novice miners get pretty excited about finding gold after an earthquake … there’s a possibility that there might be gold because there might be precipitated gold in a particular form.”

If a fault didn’t extend to the surface, however, the chance of finding gold was reduced, he said, adding he didn’t want to see “people running around with metal detectors, looking for gold in remote areas”.

The geological understanding underpinning the earthquake-gold link was based on the fact the precious metal was dissolved in geological fluids that were circulated in fault zones.

“Then when certain conditions occur gold gets deposited in these fault zones,” Dr Attanayake said.

“The recent study by Queensland University suggests that during earthquakes that pressure in the fault zones drops so dramatically that it could precipitate gold.”