Damage due to shallow tremors
SEISMOLOGISTS say the damage caused by Saturday’s earthquake is highly unusual.
While some residents in Folkestone suffered severe structural damage to their homes elsewhere in Dover, Deal, Ashford and Thanet, hardly any damage at all was caused, despite people feeling the tremors.
The earthquake measured 4.3 on the Richter Scale and vibrations were felt as far away as East Sussex and Essex. It was also felt in Calais and Boulogne.
Seismologist Roger Musson, from the British Geological Survey (BGS), said: “Normally what you get with British earthquakes is a less concentrated pattern of damage but spread out over a wide area.
“Here, the damage is quite severe but restricted to one area, while other areas have hardly seen any damage at all.”
Earthquakes occur at the boundaries of major crustal plates and the UK sits on the British Eurasion plate.
The BGS believe the shallow depth at which Saturday’s earthquake began explains why the damage centred on Folkestone. Although the epicentre was halfway between New Romney and the French coast, 12km out to sea, the depth the tremors were recorded at only 5km. Other British earthquakes have had depths of about 15km.
Mr Musson added: “The damage suffered depends on the location and depth. What happens is that the shockwaves from the epicentre will distort, which can happen in a number of ways.
“Local geology has a focusing effect on the seismic waves and the series of vibrations can arrive at different strengths and from different directions.
“It is a complex interaction but it is possible that the vibrations were distorted and ended up at Folkestone, with neighbouring areas less affected.”
Experts expected earthquakes of at least 4 on the Richter Scale every five to 10 years in Britain. But they recorded about 20 earthquakes of about 3.5 on the Richter Scale every month.
“They are much more common than people think,” Mr Musson added.