Victoria bracing to be rattled by aftershocks

WAVES of aftershocks could rattle Victoria for the coming weeks and months after the biggest earthquake in recorded history shook the state on Wednesday.

The 5.9 magnitude tremor rocked buildings about 9.15am, with the epicentre near Mansfield, about 115km northeast of Melbourne.

Workers were huddled in groups on the streets of Melbourne CBD as office buildings were evacuated, while vibrations were felt as far as Adelaide, Canberra and even Launceston.

The worst damage was recorded at the Betty’s Burgers building in Chapel St, Windsor, where bricks and debris spilt on to the footpath and road below, but authorities said it would have been a “disaster” had the quake struck closer to the city.

Victorian SES chief officer Tim Wiebusch said more than 108 calls for help were made to the service, mostly for help with building damage. There were no reported injuries.

“If the earthquake occurred in a densely populated urban area, it would have been a different result,” Mr Wiebusch said.

University of Melbourne associate professor of earthquake science Mark Quigley also said Melbourne was lucky to avoid catastrophe.

“You are seeing damage in Melbourne 150km away from the earthquake. If we were to get one of this magnitude beneath an urban centre, the damage would be catastrophic,” he said.

Most damage to the city was minor, with cases of crumbling brick chimneys, cracked walls and internal breakages recorded in homes across the city. Residents also reported birds falling silent as the tremor rumbled through the suburbs.

State Emergency Management commissioner Andrew Crisp warned that while aftershocks were likely, they were unlikely to be as severe as the initial jolt.

University of the Sunshine Coast geotechnical engineering senior lecturer Dr Adrian Mccullum said geological maps of the epicentre showed a “large number of faults”.

“Thus, it appears like an area where the release of compressive stress via an earthquake might be probable,” he said.

“These earthquakes occur because the continental plate on which Australia sits is moving north at about 7cm per year.

“This builds up compressive stress within the Australian Plate. This stress is occasionally released along preferred areas, typically, preexisting fault lines, where the earth has sheared because of these stresses.”

Australia’s most deadly quake, on December 28, 1989, in Newcastle, had a magnitude of 5.4. It killed 13 people, injured more than 160 and left a $4bn damage bill.