LONDON IS overdue for an earthquake that could cause billions of pounds of damage, a leading seismologist warned yesterday.
Britain is not close enough to any tectonic plate boundaries to suffer an earthquake like the catastrophic magnitude 7 quake that hit Haiti earlier this year. But small or moderate quakes can still cause damage.
In April 1580, a magnitude 5.5 earthquake caused extensive damage in the southeast of England and France. In London, two people were killed. The epicentre of the quake was in the Dover Straits – between England and France – 140km from London, originating 16-32km underground.
“This earthquake can certainly happen again because even the quake in 1580 was a repeat of a previous one that occurred in 1382, with almost the same epicentre, size and results,” said Roger Musson of the British Geological Survey.
Speaking at the British Science Festival in Birmingham, Musson said precise predictions of the next major earthquake to hit London were difficult. “All we can do is say that something that has happened twice can and probably will happen three times, but as to whether it happens tomorrow, in two years or in 20 or 50 years, that is something we would love to know but we don’t,” he said.
“What we can be sure of is that, in the years since 1580, the exposure of society to earthquakes has increased enormously. The same earthquake happening tomorrow will impact far more people than was the case in the 16th century.”
Britain as a whole typically gets a magnitude 3.5 earthquake once a year, a magnitude 2.5 quake 10 times a year, and around a hundred magnitude 1.5 quakes a year. Every 10 years the country will feel a magnitude 4.5 quake and, on average, a magnitude 5.5 every 100 years.
The British Isles sit in the middle of a tectonic plate that is being hit on two sides: northeast along a boundary with north Africa and eastwards along a plate boundary in the Atlantic Ocean.
Because of old geological movements, there are lots of small cracks that have developed in the plate during old phases of mountain-building. “Think of it as a dinner plate that has been broken several times and glued back together and then you’re squeezing it,” said Musson. “If one bit is not glued terribly well, then it can give a little.”
He said that a magnitude 5.5 earthquake would likely spare modern office buildings, but older Victorian buildings would be at risk.
“There was a small earthquake in Folkestone (southeast England) in 2007. What was damaged most was old chimneys – they came down. Newer houses were not damaged at all . . . It may not sound very dramatic compared to buildings collapsing but if people are walking in the street and a chimney falls on you, that’s bad news.”
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