WINDOWS rattled, slates cracked and morning cups of tea were spilt as North-East families feared they had been hit by an earthquake yesterday.

But it was not seismic friction deep under the ground but a sonic boom in the skies that caused the tremors.

Police stations in Teesside, across County Durham and into Northumberland were flooded with calls from 10.10am.

The worst of the tremors were felt in the Peterlee and Easington area of County Durham. Marjorie McIntyre, a reporter with The Northern Echo, was at her home at Old Shotton, Peterlee, at the time.

She said: "I thought, 'my God, what the hell was that?' The whole house shook, I mean really shook. There were doors flying open, the lot.

"I thought there had been an explosion.

"I ran out to the village green but everything seemed fine."

Peterlee Town Council clerk John Arthur was in the council offices. He said: "We thought the roof had gone in. It seemed like a big explosion."

The Ministry of Defence (MoD) said later that seismologists at Edinburgh University had confirmed the tremor was caused by a sonic boom.

Up to 30 jets had been taking part in a multi-national training exercise off the Durham coast. Inquiries are being made.

The effects of a sonic boom, which occurs when an aircraft breaks the sound barrier, can be felt up to 50 miles away.

An MoD spokesman said: "It is against the rules to do that over land, but mistakes do happen and we apologise when they do."