The biggest earthquake to hit parts of the NSW Hunter region in decades could have been triggered by coal mining in the region, a geophysicist says.
The 4.7-magnitude quake shook the town of Denman at 12.02pm on Friday, sparking thousands of reports of tremors in the following hour, including from people in Sydney, about 171km south.
It was originally recorded as a magnitude 5, but later downgraded to 4.7.
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It was the biggest earthquake in the area for years, but smaller than the 5.4 magnitude earthquake that devastated Newcastle, 117 km east, in 1989, killing 13 people and flattening hundreds of buildings.
Friday’s quake caused no major damage to infrastructure or buildings, and there were no reports of injuries, police said.
The NSW State Emergency Service said it had received 11 calls related to minor residential damage and reports of minor infrastructure damage in nearby towns of Maitland and Muswellbrook.
The SES said dams in the area were unaffected.
Unverified social media posts showed stock knocked on the floor of a Muswellbrook hardware store and cracks in the wall of a house in the town, said to be caused by the quake
UNSW geophysicist Stuart Clark said the quake was the biggest of six to hit the local area, a coal mining hub, in the past 50 years.
“It’s a little smaller than the Newcastle earthquake, and there was another one 5.3 (magnitude) in 1994,” associate professor Clark said.
“The cause is compressional forces across the continent but the trigger is potentially coal mining.”
He warned of aftershocks in the next two days, saying “there might be a cluster of aftershocks typically a little bit smaller than this one”.
“They don’t have to follow major earthquakes but they can.”
One resident of Muswellbrook, about 22km south of Denman, described the quake as much bigger than “just a tremor”.
“The whole house rattled, and then about half a minute later, it rattled again,” the woman said.