An earthquake measuring 3.3 on the Richter scale hit the Shetland Islands today, the British Geological Survey confirmed.
Residents were abruptly woken at 5.30 this morning by the quake, which caused a large bang and houses to shake.
Police and the coastguard said it had received a number of calls from concerned householders.
A BGC spokeswoman said the location of the quake was "quite unusual" as it was not an area known for its seismic activity.
Dr Aoife O' Mongain of the BGS said: "We have analysed the seismic activity on our chart at our Lerwick station and it has shown an earthquake of 3.3 magnitude.
"This activity has also appeared on our chart in Plockton in the Western Isles, but has not travelled as far as Edinburgh.
"People were reporting that it felt like a train had gone past right outside their house and their windows were shaking."
She added that the quake's epicentre was onshore, 12 miles north-west of Shetland.
A Northern Constabulary spokesman said: "We received a number of reports around 5.35am from residents in the Tingwall and Mossbank areas of Shetland.
"They reported hearing a bang and their houses shaking."
He added that there were no reports of any injuries or damage to properties.
Shetland Coastguard watch manager David Phillips said: "I was sitting at work early this morning when the building shook momentarily.
"We then got phone calls from members of the public who were concerned because they had heard banging and shaking.
"We have had no reports of any aircraft emergency or anything unusual happening. It certainly made us sit up and take notice."