Magnitude 4.8 earthquake rattles

Many locals were woken from sleep just after 2am on Saturday morning as a 4.8-magnitude earthquake, about six kilometres north-east of Korumburra sent tremors across the state.

The earthquake was recorded at a depth of 10km by Geoscience Australia's national earthquake alerts centre and more than 20,000 reports were received by Geoscience Australia.

The quake was followed by hundreds of aftershocks, with the majority too small to be felt, but an aftershock of magnitude 3.1 was recorded nearby, less than an hour after the main shock.

Earthquake geologist at Monash School of Earth, Atmosphere and Environment Dee Ninis said although earthquakes could and did happen anywhere in Australia, the Gippsland basin was a region of heightened seismic activity relative to some other regions, and Korumburra was no exception.

"In 2009, a magnitude 4.7 was followed by a similar magnitude earthquake about two weeks later. The same area experienced a magnitude 4.4 quake in 2011.

"The area is known for several geological faults which first accommodated extension of the earth's crust to form the Gippsland Basin more than 100 million years ago," explained Dr Ninis.

"In more recent times, in the last 5 million years, these faults were reactivated to accommodate compression of the crust, resulting in uplift and mountain building. These compressive forces continue in the present day, and earthquakes like this one are the sudden release of stress that has built up in the crust as a result of these forces."

Aftershocks associated with Saturday morning's earthquake are expected to continue over the next few days to weeks and these are expected to become smaller and less frequent with time.
However, Dr Ninis said as with all aftershock sequences, there was a chance an earthquake of similar magnitude or larger may occur.