An earthquake that rattled parts of Victoria is likely an aftershock from a 2021 quake.
No damage has been reported after the magnitude 4.1 tremor struck Woods Point, a small town about three hours' drive east of Melbourne, just before 4am on Wednesday.
Geoscience Australia senior seismologist Phil Cummins considered the event an aftershock from Victoria's record 5.9 magnitude earthquake in September 2021.
That quake damaged buildings in Melbourne and was felt as far away as Canberra, Sydney and Adelaide after spreading from its epicentre in Mansfield, about 60km from Woods Point.
"The physical size of the earthquake today was about 100th that of the earthquake that occurred in 2021," Prof Cummins told AAP.
"The energy released would be ... about nine hundred times less than than the energy released in that previous earthquake."
There have been about a dozen earthquakes of magnitudes higher than three in the area since the 2021 event.
The tremor was felt as far away as South Morang in Melbourne's north, Healesville in the Yarra Ranges, Wangaratta in the state's north and Dargo in East Gippsland, according to Victoria's State Emergency Service.
Vic Emergency still warned people to watch out for any minor damage and aftershocks.
"Stay safe by avoiding damaged buildings, roadways and bridges, and fallen trees and powerlines," an alert stated.
Aftershocks occurring years or decades after initial earthquakes were common, Prof Cummins said, and more could follow.
"It's not unusual for large aftershocks to have their own aftershocks," Prof Cummins said.
"But I would expect the earthquakes we see immediately after this earthquake to be considerably smaller."
While Australia didn't have an active tectonic plate boundary like in New Guinea or New Zealand, stress from other boundaries slowly built up to the interior of the plate, eventually causing faults to fail, Prof Cummins said.
"They just fail at a much lower rate than they would where near tectonic plate boundaries, where the strain rates are much faster," he said.
More than 1900 people reported the earthquake to the government agency, which recorded the epicentre as 8km underground.
The Bureau of Meteorology said there was no tsunami threat to Australia.
It's the largest earthquake to strike the area since June 2023, according to the Seismology Research Centre.
The Tenant Creek earthquakes of 1989 are still producing aftershocks, 35 years after the event.
The 7.2 to 8 magnitude New Madrid earthquakes in the eastern part of North America were still believed to be providing aftershocks more than two centuries later, Prof Cummins said.
"So it's really not a surprise that this aftershock sequence would last this long," he said.
