Mansfield Courier

Mansfield still rocks

Aftershock­s abundant following quake, with landslip and cracking activity noted around local area

- BY SHAUN McMAHON smcmahon@

THE recent earthquake on September 22 made headlines across the globe, with news crews flocking to Mansfield to interview local residents and business owners.

The epicentre of the earthquake was recorded outside of Woods Point, and it measured a magnitude of 5.9 the biggest experience­d in the eastern states.

Several aftershock­s have since occurred, with magnitudes ranging from the mid twos to low threes in scale, and the local community have felt many of these, with people posting pictures and videos on social media.

“We recorded nine aftershock­s in the 24 hours following the main quake, and there may be more in the coming weeks and even months,” said Dr Hadi Ghasemi, senior seismologi­st at Geoscience Australia.

“However, it is important to note that it is not possible to predict precisely when or how large these earthquake­s may be, or when the sequence will diminish to a point where they are no longer detectable.”

In the wake of the recent earthquake, Associate Professor Dr Mark Quigley and his team from the University of Melbourne travelled to the local region for four days to examine how the earthquake acted as energy dispersed from the epicentre.

Dr Quigley conducted an online Q&A session through council for the Mansfield Shire last week and provided details about the earthquake to a number of curious local residents.

“This earthquake is a story about things that happened and things that didn’t happen,” said Dr Quigley.

“Structures, such as an old house in Jamieson with a brick chimney, would have been expected to fall considerin­g the shaking, but it didn’t.

“Then we had rock slippage that may not have been expected.”

Dr Quigley explained that earthquake­s are not uncommon in Australia, but it’s a bit like throwing a dart at a large dartboard, considerin­g the size of our country, as to whether we feel it.

Although Australia is not on a fault line, where earthquake­s occur more frequently on the plate boundaries, plate interiors also get strained at times.

“The Australian (tectonic) plate is moving 6cm per year towards Papua New Guinea, and it’s fringed with a plate battery that is resisting aspects of motion.

“This is the cause of earthquake­s, in our case, pushing from New Zealand and Sumatran plates.”

Dr Quigley elaborated that our region in the North East is warm and a high seismic hazard area relative to the rest of Australia, but that doesn’t necessaril­y equate to higher risk.

“We think there’s a fault four to 14km below the surface of where this earthquake occurred near Woods Point,” said Dr Quigley.

“Fifteen minutes after the main shock was a four-plus magnitude aftershock.

“There are often hundreds of smaller aftershock­s, but the rate of these decays in time.”

Local resident John Nichols recently posted footage of landslip activity, with rocks partially blocking the road between Kevington and Gaffney’s Creek.

A number of residents commented, some feeling the movement and others not noticing it.

Cracking along the Jamieson-Licola Road was also observed.

Australia experience­s one to two earthquake­s at a magnitude of five or more each year.

In 2018 Lake Muir in Western Australia, approximat­ely 330km from Perth, had earthquake­s measuring 5.2 and 5.3 magnitudes, and Wonnangatt­a experience­d a 5.4 magnitude earthquake in 1982.

In 1989 Newcastle NSW recorded an earthquake at 5.6 on the Richter scale, in which 13 people lost their lives, 160 were injured and 300 buildings were demolished.

About every 10 years or so, Australia experience­s an earthquake at a magnitude of 6.0 or more, as seen in the WA town of Meckering in 1968 (magnitude 6.5) and Tennant Creek NT in 1988, which was the largest on record in Australia at a magnitude of 6.6.

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 ?? PHOTO: courtesy of Wellington Shire Council ?? CRACKED: Although no significan­t damage was noted in the Mansfield Shire, neighbouri­ng Wellington Shire experience­d cracking on the Jamieson-Licola Road.
PHOTO: courtesy of Wellington Shire Council CRACKED: Although no significan­t damage was noted in the Mansfield Shire, neighbouri­ng Wellington Shire experience­d cracking on the Jamieson-Licola Road.

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