Why the earth keeps shaking in Victoria

Victoria has been shaken a total of 17 times this year, setting nerves on edge. Here’s what’s behind this spate of earthquakes.

The earth has moved in Victoria yet again, with residents of Pakenham and Melbourne’s east jolted awake by a magnitude 2.5 earthquake overnight.

Why does it keep on happening? And are more on their way?

IS VICTORIA GETTING MORE EARTHQUAKES THAN USUAL?

Yes – but only slightly.

Geoscience Australia data shows Victoria has experienced 17 earthquakes measuring more than 2.0 on the Richter scale since January 1 this year.

The strongest was a quake measuring 4.6 which struck in the early hours north of Rawson last Friday.

The second strongest measured 4.0 and hit northeast of Sunbury late on May 28, followed two minutes later by an aftershock measuring 2.6.

The 17 disturbances this year are “a little more than average, but over the longer term not that unusual,” said Jonathan Griffin, senior seismologist with Geoscience Australia.

“Last year we got five of similar magnitude. Earthquakes are largely random events and sometimes we get them closely spaced in time.”

DO THESE RECENT MOVEMENTS RELATE TO THE BIG GIPPSLAND QUAKE?

The 5.9 magnitude earthquake which struck at a depth of 10km near Licola North in Gippsland on September 22, 2021, remains the most severe ever recorded in Victoria.

(The largest in Australia hit a remote part of Western Australia in 1941. It registered 6.8 but created little damage.)

The Gippsland quake caused damage as far away as Melbourne’s South Yarra, when brickwork on the Betty’s Burgers eatery fell onto Chapel Street. There were nine aftershocks in the 24 hours following the main quake.

Debris in Melbourne’s Chapel Street after the 2021 earthquake. Picture: Mark Stewart

Most – but not all – of the recent quakes are unrelated to the 2021 event.

“Last Friday’s 4.6 earthquake near Rawson is an aftershock of the 2021 event,” Mr Griffin said. “But with the others, they’re too far away for us to understand how they are linked.”

COULD A BIG EARTHQUAKE BE COMING?

“We can’t predict earthquakes; what we can do is forecast the probability,” said Mr Griffin. “Having one earthquake does the increase the likelihood [of future movement] a little bit, but not by a lot.”

Damage from an earthquake depends on a range of factors, including magnitude, depth, distance from population centres and building quality, Mr Griffin said, but it’s usually quakes of magnitude 4.5 and above that cause significant problems.

Jonathan Griffin, senior seismologist with Geoscience Australia. Picture: Supplied

According to Geoscience Australia, Victoria has experienced five earthquakes that registered 3.0 and above in the past five years. Australia as a whole usually gets 100 such tremors and quakes every year.

The country’s most destructive earthquake was in Newcastle in 1989. Measuring 5.6 on the Richter scale, it resulted in 13 fatalities, damaged 50,000 buildings and led to $4.24 billion in insured losses, according to the Insurance Council of Australia.

IS VICTORIA MOVING MORE THAN THE REST OF AUSTRALIA?

We think of the Great Southern Land as a big immovable mass, but the reality is actually quite different.

On Tuesday, the earth also moved near the Northern Territory/South Australia/Queensland border, which experienced a 3.0 quake, and near Darkan, Western Australia, which rumbled with a 2.4 tremor.

On Sunday, a 2.8 quake was felt in WA’S Great Victorian Desert, and on Monday the earth moved in northwest Tasmania, with a 2.5 shake.

Victoria’s recent spate of activity may be unnerving for residents experiencing the shakes, but it’s not the worst series of earthquakes ever experienced in Australia.

Residents of the Dalton-Gunning area near Canberra experienced six big shakes in the space of just four years in the 1930s.

Locals were shaken by a 5.0 quake in 1930, one measuring 4.8 in 1933, and four in 1934, registering 4.7, 4.8, 5.6 and 4.8 respectively.

Originally published as Why the earth keeps shaking in Victoria