Debate about the cause of two earthquakes and multiple tremors that rattled the Upper Hunter in recent days continues to rage.
While some maintain the removal of millions of tonnes of earth by the mining industry was the catalyst for the seismic activity, others point to the region's geological structure and long history of tremors and quakes.
A fault line, known as the Hunter-Mooki Thrust, forms the boundary between the Sydney Basin Rocks in the south of the Hunter and the New England Fold Belt to the north.
Movement in a fault line has been cited as the cause of more than 100 tremors recorded in the region in the past two decades.
But some locals maintain coal mining at least contributed to the 4.8 and 4.5 magnitude quakes that struck on Friday and Saturday.
Those prosecuting the argument point to the fact that the epicenter of Friday's quake was beneath Mt Arthur coal mine.
UNSW Sydney associate professor Stuart Clark said on Friday that while compressional forces across the Hunter were the cause of the quake, its trigger was potentially coal mining.
Camberwell resident Deidre Olofsson cited recently published research showing a link between mining and seismic activity in the coal mining in Europe.
"If you look around you can see there is a relationship between where the mines are located and the earthquakes, particularly where there are fault lines," she said.
Ms Olofsson said her initial reaction to Friday's quake was that it was an errant blast at a nearby mine.
She said she maintained that blasting, which dislodges thousands of tonnes of rock, may have triggered the quake.
"It would be interesting to know if there were multiple blasts occurring at the same time," she said.
Muswellbrook local Pete Kennedy was at a business on Denman Road when Friday's quake struck.
"There was a little bit of noise then the whole building started shaking. It lasted between five and 10 seconds; it was a good shake," he said.
"I lived in New Guinea for a few years and they were quite commonplace so it didn't really bother me. I knew what it was."
He is of the firm view that seismic activity was not related to mining.
"I know there has been a lot of dirt shifted around but these tectonic plates that are moving around deep in the earth are the culprit, not the mines," he said.
Like others, Mr Kennedy said he feared the implications for building a nuclear power plant, as proposed by the federal Coalition, in the Upper Hunter.
"It will be very expensive and take years before we get anything out of it. Aside from that, to build it in an area where there is regular seismic activity makes no sense. It's not for me."
Ironically, Bulga resident John Krey, whose property has previously been rattled by tremors and blasts, did not experience Friday or Saturday's quakes.
"Maybe it's because the land is so riddled with massive holes now, but we didn't feel it," he said.
