Scientists are now warning that volcanoes in Western Victoria and South Australia are due to erupt.
The prediction comes just hours after two earthquakes hit the state this morning.
Using new dating techniques, University of Melbourne scientists have found that the volcanoes usually erupt every 2000 years, with the last eruption at Mt Gambier, South Australia, 5000 years ago.
Earth sciences Professor Bernie Joyce says Australia needs a plan in case of an eruption.
It comes as Victorians are warned to brace themselves for more tremors after a shallow magnitude quake hit at 11.32am, sending shockwaves through towns and suburbs more than 100 kilometres away.
A series of tremors lasting up to 15 seconds have been felt across Melbourne's CBD and southeastern suburbs.
A second, smaller quake shook Korumburra, with reports it was again felt in Melbourne, at 12.37pm
Senior seismologist Clive Collins said people should prepare for aftershocks in the coming hours.
"There will be aftershocks, that's a certainty," he told the Herald Sun.
"We still expect lots of smaller ones.
"After the last significant quake in Victoria there were more than 200 aftershocks."
The tremors shook Melbourne office buildings and many homes across the state, including Warragul, Ferntree Gully, Sunbury and as far north as Melbourne Airport.
Seismologist Adam Pascale told 7News it was the largest quake recorded in the area in the past two years, and warned there is potential for stronger tremors.
"It's significant for Australia, particularly because it was so close to an urban area," he said.
"There's potential for larger events in this sequence.
"We have had a 4.5 in the past, this is a 4, but we could have larger again. There's no way of predicting what the magnitude could be."
Some Victorians say their houses shook violently for about 10 seconds, and many reported hearing the earth rumble.
Daniella Augelli told 7News: "It was like a big push against the house, but at the same time it was vibrating.
"It was just a few seconds of terror."
She has cracks in her wall, as do the Bruch family in Croydon.
Damian said: "I was about to get up and make a coffee and I noticed the house shaking.
"I said to my daughter, Bridgette, 'what's that?' and she looked up and said 'earthquake'."
Bridgette said it felt like the couch had moved.
Deek from Ferntree Gully told 7News: "Our house is on stilts and moved considerably for a few seconds. No damage though."
Anne from Glen Waverley said it felt like a goods train had passed under her home.
"I was sitting on the bed looking out of the window," she explained.
"I could hear the roof tiles clattering and then the house shake along with me. It almost felt like a goods train was passing underneath the rumbling ground."
Karina Fitzgerald, from Cold Stream, said she mistook the earthquake for an explosion. "Our home shook as if an explosion had happened nearby," she said. "Our cat and I just looked at each other wondering what it was, now I know."
Veronica Francis said the tremors were also felt in Darnum.
"Talk about spooky," she said. "It went on for quite a long time."
Korumburra Hotel publican Troy Patterson said when the earthquake hit, the pub shook for about eight seconds, accompanied by a loud rumbling.
"The whole place literally shook," he told AAP.
"You would think a truck had driven through the pub."
Many also took to Twitter to detail their experiences.
One user Kate Forster wrote: "The earth is so strong the earth just shook."
Lois Ath wrote: "Felt like a train going through my house here in Warragul."
Experts say the quake struck 8 kilometres underground, and said the epicentre was about 7km west of Korumburra.
So far, there are no reports of any major damage, except hairline cracks in some peoples' homes.
A spokesman for Geosciences Australia said the centre had received more than 300 reports from people who felt the quake. Most reports were of windows and crockery rattling, he said.
The area in Gippsland is prone to small earthquakes, with a number of tremors measuring between 1.8 and 4.6 originating in the same area in March and May 2009.
Did you feel the earth tremor? If so, email the news desk by clicking here