A 3.8-magnitude earthquake struck north Wales on Wednesday, with tremors felt as far away as the Irish capital Dublin, but there were no reports of damage.
The epicentre of the earthquake in the Irish Sea was 15 kilometres (9.3 miles) from the Welsh seaside town of Abersoch on the Llyn Peninsula, the British Geological Survey (BGS) said.
Residents as far as 140 kilometres away reported "intense shaking" during the earthquake, which happened at around 4.15 am (0315 GMT).
"This was a larger than average earthquake, we get around one a year of this size," the BGS said.
"People have reported hearing an initial loud banging, followed by rumbling, and intense shaking."
Britain experiences some 200 earthquakes every year, according to the BGS -- most of them so small that no one even notices them.
The largest ever British quake struck in the North Sea in 1931, with a magnitude of 6.1.
As the epicentre was 120 kilometres offshore it caused only minor damage to buildings on the eastern coast, but the tremors were felt as far away as Germany and Denmark.