Underground operations at the Cadia Valley Operations gold mine have been temporarily suspended after a magnitude-3.4 earthquake struck the site early Friday morning.
According to Geoscience Australia, the earthquake occurred at approximately 5:45am and was centred about one kilometre underground within the mine site, located south of Orange in the state's Central West region.
Mine operator Newmont Corporation confirmed that all underground workers were safely brought to the surface following the tremor. The company said there were no reported injuries and that inspections were being conducted before underground activities resume.
The quake was felt across several Central West communities, including Orange, Millthorpe, Blayney and Oberon. More than 100 residents reported experiencing the tremor through Geoscience Australia's monitoring system.
Blayney Shire Mayor Bruce Reynolds described the sensation as similar to "a very big truck" approaching, saying the shaking lasted for about five seconds.
Earlier the same morning, a separate magnitude-3.2 earthquake was recorded northwest of Wilcannia near Mutawintji National Park. Only two people reported feeling that tremor.
Friday's earthquake marks the second significant seismic event affecting the Cadia mine in less than three months. In April, a magnitude-4.5 earthquake struck the region, forcing the suspension of underground operations for five weeks. During that event, workers were trapped in underground refuge chambers for more than 10 hours before being safely rescued.
The April quake was the strongest earthquake ever recorded in the Orange region and was felt across a large area including Sydney, Canberra and Wollongong. Prior to that event, the region's largest recorded earthquake was a magnitude-4.3 tremor in 2017, which also resulted in precautionary evacuations and operational disruptions at the mine.
Mayor Reynolds noted that Friday's quake was considerably weaker than the April event, describing the earlier magnitude-4.5 earthquake as several times more violent.
Cadia is one of Australia's largest gold mining operations and plays a significant role in the economy of the Central West region. Because of the depth and scale of underground mining activities, safety protocols require operations to be halted following seismic events until inspections confirm conditions are safe.
Engineers and safety specialists are now assessing underground infrastructure and mine workings before a decision is made on when normal operations can resume.
