A sonic boom caused by an American F-15 fighter jet carrying out a supersonic run was behind a mysterious "tremor" felt across Norfolk on Thursday and not an earthquake, the Ministry of Defence (MoD) said.

Norfolk police received a flurry of calls shortly after midday from worried residents reporting a possible earth tremor - and the strange event was the talk of the force's Wymondham headquarters where members of staff also felt the earth move.

But experts quickly moved to reassure local people that the tremor was not an earthquake and was most likely to be a sonic boom, which is caused by an object moving faster than sound, usually an aircraft.

Glenn Ford, a seismologist with the British Geological Survey, said: "It certainly wasn't an earthquake. From the observations I have been given, they are very consistent with sonic booms we have received from the area historically over the last 20 years. I cannot say for definite that this was the cause, but looking at the evidence that would be the most likely source of the activity.

"We have scrutinised all the data from the nearest stations. For an earthquake to be felt so widely, as this has, it would have to be pretty large. Even if one of these stations had failed, we would have seen evidence from others across central England.

"We have contacted the RAF but at this time unfortunately they have not been able to corroborate that there has been a sonic boom. This could come from an aircraft or even a falling satellite or meteorite."

A Norfolk police spokesman said: "We received a number of calls from people reporting a possible earth tremor in the Wymondham area. We felt the tremor ourselves in the office. A member of the public suggested it was caused by an aircraft breaking the sound barrier." The spokesman said there were not thought to be any reports of any serious damage.

Nicky Germaine, 22, was at home in Wicklewood when she felt the tremor at about 12.20pm. "It rattled my house and it opened my porch door," she said. "I just thought that a lorry had gone past but then I turned on the radio and heard other people reporting similar stories. It was a bit weird. I thought it was an earth tremor."

Rosalind Ross, 60, was standing outside her home in Spooner Row when she felt the strange tremor. "I was standing outside the back door and the ground really shook under my feet. It was so loud. There was a roar like a fleet of beet lorries going past.

"It bothered me a little bit because I was standing on my own and the ground shook really violently up through my feet."

John Rix, proprietor of Poppa Johns barbers in Wymondham, said: "Three of us were cutting when we heard the front window shaking. I have been here 14 years and that window has never moved before. I said it must be another earthquake but someone else said it was a sonic boom."

A Ministry of Defence (MoD) spokesman confirmed that the sonic boom was caused by an American F-15 fighter jet carrying out a supersonic run. "The aircraft from RAF Lakenheath was flying above 10,000ft at the time of the run," the spokesman said.

An RAF Lakenheath spokeswoman confirmed there had been an aircraft in the area when the incident was reported, but said she was unable to confirm what it was.