NSW hit by 4.5-magnitude tremor in state’s central west
Updated ,first published
A record earthquake near a gold mine in central west NSW shook the ground as far away as Sydney and Batemans Bay.
The 4.5 magnitude earthquake, about 35 kilometers southwest of Orange, occurred at 20:19 on Tuesday.
Nearby residents reported a roar lasting 10 to 15 seconds and compared the sound to a jumbo jet. Those closest to the epicenter said the explosion was like a bomb.
“It was like an explosion under the house,” said Blayney Shire mayor Bruce Reynolds, who lives 12 kilometers from the epicentre.
Reynolds said it was more powerful and sudden than the 4.3 magnitude earthquake that struck a similar location on Good Friday in 2017.
“This was different,” he said. “This is probably the biggest thing we’ve seen in this local area in modern history since the first use of the Richter scale.”
Sofas flew in Mittagong, houses creaked in Lawson, windows rattled in Bathurst and cats became active in Caringbah, people reported on social media.
The biggest concern was miners working underground at the Cadia gold mine near the epicenter, who had to be evacuated.
Newmont Cadia, the operator of the mine, confirmed in a statement that its seismic sensors detected the earthquake and that its employees were safe.
Geoscience Australia senior seismologist Dr Phil Cummins said in some cases other human activities such as mining, fracking and wastewater injection could cause ground tremors, but it was very difficult to establish a direct link between a mine and a specific earthquake.
“Mining can change the ‘stress field’ around the world, and a change in the stress field could potentially trigger an earthquake,” he said. “The problem is that our network that we use to track earthquakes at the national level is too crude to identify this mechanism with any accuracy.”
The extraction and deposition of large amounts of material underground and the movement of water around can change how tectonic stress is distributed and affect seismic activity, he said.
“Some papers were able to relate the change in seismic activity to changes in mining activity, particularly things like fracking, and draw a correlational relationship,” he said.
Intensive, local monitoring of seismic activity over a long period of time will be required to better understand whether specific mining activities trigger tremors or earthquakes.
Cummins said there have been four earthquakes above magnitude 3.5 in the immediate vicinity of the Cadia mine since 2017. He said the earthquake that occurred on Tuesday night was the largest earthquake ever felt in the region.
Prime Minister Chris Minns was asked on Wednesday morning whether he had been briefed on a possible link between the earthquakes and the mine.
“We do not believe this is related, nor have I been given any information that it is connected. I was notified of this late last night,” Minns said.
Earthquakes can occur on the continent due to forces exerted on the boundaries of the Australian tectonic plate. “Although these boundaries are very far away, the stress in the Australian crust is slowly increasing, so earthquakes can happen anywhere,” Cummins said.
More than 2000 people reported feeling the latest earthquake to Geoscience Australia.
“The weak tremor extends at least several hundred kilometers to the southeast into Batemans Bay,” Cummins said.
Within 30 minutes of the earthquake, two aftershocks of magnitude 2.4 and 2.2 occurred in the midwest.
Police have no information on injuries or damage. Reynolds said NSW Recovery Minister Janelle Saffin had been in touch to offer support.
Because the Richter scale is logarithmic — meaning each number represents a 10-fold increase in intensity — a magnitude 4.5 earthquake is approximately 1.6 times larger than a magnitude 4.3 earthquake, but twice as powerful in terms of energy released.
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Angus Dalton is science correspondent for The Sydney Morning Herald.Connect with: X or email.
