An earthquake measuring 3.5 on the Richter scale has shaken parts of Dumfries and Galloway.
The tremors were felt in and around Dumfries
People living in and around Dumfries said they felt two tremors at about 1040 GMT on Boxing Day.
Police said they had been inundated with calls from people reporting the earthquake, which was also felt by people living in Lanarkshire.
Retired teacher Meg Edgar, who lives on the outskirts of Dumfries, told BBC Scotland it was "really frightening".
She said she had heard an "almighty, thunderous crash" on the roof as she went to put away Christmas presents.
She said: "I really thought somebody was trying to break in through the roof.
"My immediate thought was that it can't be Father Christmas because it is a day too late, but it was really frightening."
The British Geological Survey said the earthquake was the largest in the UK this year.
Bennett Simpson, a seismologist with the BGS in Edinburgh, said: "This was a significant earthquake, but we would expect one or two of this magnitude every year.
"We have taken a number of calls from people in the Dumfries area reporting windows rattling, houses shaking and hearing a large bang."
The Edinburgh-based BGS has created a web page - at www.earthquakes.bgs.ac.uk - where people can send their experiences of the quake.
A police spokesman in Dumfries said it had lasted for about 10 seconds.
"We weren't sure what it was, then the phones started ringing and they haven't stopped. It was actually scary," he said.
The spokesman added that no injuries or damage had been reported.
Marie Brown, a receptionist at the Station Hotel in Dumfries, said: "I was sitting in the bar downstairs and all of a sudden I thought there was a convoy of trucks going past. But it didn't stop.
"The walls then started shaking and I became quite frightened. My fiancÚ is a builder and he looked at me and said 'This isn't good', but then it stopped.
"It was a scary moment for us but everything seems to be okay."