The earthquake that damaged nearly 500 homes in the south east corner of Britain could have been on a far bigger scale, experts said last night.

Seismologists have been expecting a quake off the Kent coast for decades and feared a repeat of fatal tremors that struck in the past and registered 5.8 on the Richter scale.

Although houses in Folkestone, Kent, were damaged by Saturday’s earthquake, which measured 4.3 on the Richter scale, only one person was injured, not seriously.

Roger Musson, of the British Geological Survey, said: “We’ve been waiting for an earthquake to happen on this structure for a long time. I’ve been very concerned about getting a repeat of the 1580 earthquake. If that had happened, we would have had a death toll that would have exceeded the death toll of all British earthquakes by a factor of five – perhaps as many as 50 dead. If that fault is true to form, then it’s good news because its got that out of its system.”

Shepway District Council said that the quake, with an epicentre 14km (9 miles) south of Dover, had left 73 houses in Folkestone too dangerous to inhabit. The council has advised the owners of a further 30 houses not to return home until inspections have taken place.

A spokesman for Eurotunnel said that the Channel Tunnel was unaffected by the earthquake. “It was built with tremors in mind,” he said. “It’s built to survive earthquakes with a significantly higher magnitude than the one on Saturday.”

The Association of British Insurers said that the total cost of damage could run into tens of millions of pounds. A spokesman said: “The last serious earthquake that struck Britain in Dudley resulted in a bill of around £15 to £20 million.”

The Dover Straits has been the epicentre of two powerful earthquakes, in 1382 and 1580, measuring 5.8 on the Richter scale. Saturday’s earthquake, the biggest in Britain since 2002, struck at 8.18am, as most Folkestone residents were still in bed. A 30-year-old woman sustained minor injuries.

Those caught up in the earthquake talked of cracking walls and falling brickwork. The Foord area of the town took the brunt of the tremor, with chimney stacks falling into the streets. Almost 100 people sought refuge in a centre set up by the Salvation Army, where about a dozen temporarily homeless residents spent Saturday night. Captain Peter West, a Salvation Army minister, said: “A lot of people were upset and confused but there was no serious trauma.”

Hilary Bourne, 59, who spent the night at the centre, said: “We have taken a walk back home to have a look at the house but my husband and I are still in deep shock.

“Our street looks awful, with fallen chimneys, bricks and roof slates everywhere. Our cat went missing during the shake and I am worried she is buried under the rubble. Our dog is all right but he had to spend the night in police care.”

Kent Fire and Rescue Service took more than 400 emergency calls on Saturday, ranging from structural damage to gas smells. Charlie Hendry, chief fire officer, said: “If you think in a normal weekend we would have about 60 or 70 calls, it gives you an idea of the magnitude of the demands on our services.

“It was an extremely scary experience being shaken out of your bed at 8.20 in the morning and most people were very confused, and it was a very confused picture. I think in some ways it was really miraculous that more people didn’t get hurt.”

Electricity and gas supplies to houses in some parts of Kent were cut off but later restored. Scottish and Southern Energy, which supplies gas to the area, investigated 300 “possible gas escapes” in the system. EDF Energy, the local electricity supplier, said that several thousand customers had temporarily lost power.

Michael Howard, the MP for Folkestone and Hythe, said he thought that the town had escaped remarkably lightly. “Obviously there is a fair amount of damage and it is tough on all those people who weren’t able to spend the night at home. It could have been so much worse, so I think we are really grateful that we came out of this as a community relatively unscathed.”

Between 200 and 300 earthquakes are detected in Britain every year. Tremors registering between 4.0 and 4.9 on the Richter scale hit the mainland on average every two years.

The earthquake has helped seismologists to understand fault patterns under the English Channel. Dr Musson said: “It’s very difficult to map faults out at sea. Saturday’s earthquake was helpful in the imaging of that fault. We now know the alignment – that it is angled towards the North East.”

Earth movers

—Seismologists chart historic quakes by examining monastic records for evidence of the effects

—Tremors have been recorded as early as 1120, in the Vale of Trent. Shakespeare spoke of a tremor in Kent in 1580, in Romeo and Juliet

—Britain is hit by up to 300 quakes a year. The most powerful was in June 1931, when one measuring 6.1 on the Richter scale struck 60 miles out in the North Sea, twisting a church spire at Filey, North Yorkshire

—11 people are thought to have been killed, or committed suicide, during quakes in Britain. Five people are thought to have been killed in 1884 by a tremor in Colchester, Essex

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