Hundreds of western Lake Macquarie residents were left shaken and a little stirred following the demolition of a concrete storage bin at the former West Wallsend Colliery on Thursday afternoon.
The controlled explosion, which occurred at 12.35pm, was felt between West Wallsend and Warners Bay.
A Glencore spokesman said the blast, which had been planned for months, was part of the decommissioning of the former underground mine.
“We attempted to notify as many people as we possibly could,” the spokesman said.
“It was a controlled and planned explosion that was carried out as intended.”
It may have gone to plan but social media was abuzz within minutes with anxious residents searching for an explanation of what they had just experienced.
Gayle Williams, who owns Amblside Antiques Boolaroo, said she held her breath and watched as the awning of her Main Road shop started shaking.
“Everything in the shop was shaking. I was thinking I have got to get out of the here,” she said.
Gail Paterson from nearby Second-Love Treasures compared the incident to the 1989 earthquake.
“It was definitely similar, but it didn’t go for as long,” Ms Paterson said.
“The first thing I did was ring my daughter at Warners Bay. She said they felt it over there as well.”
Seventh Street Boolaroo resident Mel Murrary said she initially thought a car had hit her house.
“It definitely felt like something had hit the house or exploded; it was a massive shock,” she said.
Geoscience Australia, the official source of information about earthquakes and tremors, had no record of the incident.
“We will often record a mine explosion up that way (Hunter Valley) as a tremor, but in this case we haven’t recorded anything,” a spokesman said.
Lake Macquarie police said the explosion had not been reported as an incident.
The mine opened in 1969 and operated as a bord-and-pillar mine until 1987, when it switched to longwall operation.
Glencore announced its closure in March 2015.
West Wallsend ran into problems in August 2013 when the Newcastle Herald revealed cliff falls and other problems in the Sugarloaf State Conservation Area above the colliery.
Production stopped for some weeks in June, 2015 after a “face fall” in one of the mine’s longwall panels.
In August, Glencore announced the longwall equipment would be left underground at the site of the face fall.
Production was also impacted by a roof fall on 11 October, 2015.