Collapsed chimneys, power outages after 4.8 magnitude earthquake shakes NSW

A 4.8 magnitude earthquake has shaken parts of New South Wales, forcing schools to evacuate and causing damage to homes.

The epicentre of the quake was near the mining town of Denman, about 250km north of Sydney, at 10km deep just after 12pm.

There have been no reports of any serious injuries in the nearby mines at Denman, NSW Resources said.

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It's understood the quake hit directly underneath BHP's Mt Arthur Coal mine.

A few miners suffered minor injuries from falling items, but no one was seriously hurt, a spokesperson for the company said.

Mining areas within the impacted site are being inspected before workers return, they also said.

The quake, which was initially reported as having a magnitude of 5.0, was later revised to a moderate 4.8.

Dr Hadi Ghasemi from Geoscience Australia said they measured a few aftershocks, with the biggest being 2.9 magnitude at 12.15pm.

He also explained what caused the earthquake.

"[There's] a slow build-up of stress that is caused by the Australian plate itself moving to the northeast, by a rate of 7cm per year," he said.

"This accumulated stress, over the years, will be released in the form of earthquakes."

Over 2000 people reported that they felt the shake, stretching from Dubbo, all the Muswellbrook, Newcastle, Port Macquarie, and even parts of Sydney including Mt Druitt, parts of the CBD, North Ryde, Kogarah, Vauclause and Revesby.

There were also reports it was felt in the Blue Mountains, in Lithgow, Blackheath and Katoomba, as well as in Picton, west of Sydney.

"The tremor...it was a massive earthquake, the whole house rattled," a listener told 2GB.

"The whole car was rocking around," another said.

Muswellbrook South Public School sent a message to parents saying the students had been evacuated.

"Muswellbrook South Public School staff and students have safely evacuated to our top oval awaiting further instruction," the message read.

St James Primary School also sent a message out to parents, saying the school had no power.

"We are all ok. Out on MacKillop [street]. We have no power so if you can please come and get your kids," the message read.

Panels on the roof of a local Aldi fell, as did stock at a nearby Mitre 10.

The State Emergency Service in Muswellbrook has told 9News that the earthquake broke the windows at the council depot, with multiple reports of damage to homes, including collapsed chimneys.

There have been six calls for assistance to the SES in both Muswellbrook and Maitland for minor damage.

More than 2500 customers in Muswellbrook, Denman, Jerrys Plains, Bureen, Bengalla, have reported power outages to Ausgrid following the quake.