Ms Simmons’ colleague, Clare Hailes, from North Lancaster, said the force of the tremor set the shop’s alarm off.
“I know the general manager got a call in the middle of the night because it set the alarms off,” she said.
“Customers have been talking about it all morning. They thought a lorry had crashed into a building or there had been a quarry explosion. No-one was expecting it to be an earthquake.”
Lancashire Police said there had been a “minor earthquake in the area, near to the Lancashire and Cumbria border, measuring 3.3 magnitude”.
It added: “There have been no reports of anyone injured or damage caused but we have officers in the area, together with colleagues from the Lancashire Fire and Rescue Service and the North West Ambulance Service.”
The Volcano Discovery website said it had received more than 1,000 reports about the earthquake, with some as far away as Blackpool.
One Carnforth resident posted on the site: “Heard a rumbling sound which intensified in to a loud bang. Thought my roof was collapsing or something! Very scary.”
Another, in Silverdale, posted: “Loud rumble and rattling of fixtures in house, as though something had collapsed or the chimney had fallen off. Significant enough to go outside to check.”
BGS detects about 300 earthquakes every year in the UK, but only about a tenth of these are felt or heard by people.
