A Bedfordshire town has been rocked by two earthquakes in one day – and four in two weeks – with residents reporting houses “shaking and shaking”.
The 3.0 and 2.1 magnitude tremors concentrated around Leighton Buzzard at around 8.32am and shortly after 12.30pm on Tuesday, the British Geological Survey confirmed.
They were thought to be aftershocks following an initial 3.3 magnitude earthquake – then upgraded to 3.5 – on Sept. 8, leaving locals speechless.
‘It was a bang and it was a jolt, a real jolt,’ said Sheila O’Connell, an NHS worker who lives in Leighton Buzzard, while another said the tremors ‘almost shook me out of bed “.
In fact, the UK sees more earthquakes than you might realize.
Why do earthquakes happen in the UK?
Glenn Ford, a seismologist at BGS, said Tuesday’s quake would be classified as an aftershock from the earthquake two weeks ago.
“They’re not happening more frequently in the area – they’re happening all the time in the UK,” he told the Standard.
“What’s unusual about them is that only about 10% feel them. We don’t really perceive the UK as a country associated with earthquakes, so when they do happen, it can be quite unnerving.
“But it’s very typical behavior seen in the UK and we’ve had historical activity in that area. Most of them are so small that people don’t notice them.”
Mr Ford said Britain sees around three magnitude 3.0 earthquakes each year, but that is a billion times smaller than the devastating magnitude 9.0 Tōhoku earthquake in Japan in 2011.
The Bedfordshire quake started several hundred meters below the surface, on hidden fault lines, experts have said.
Dr Matthew Blackett, a natural hazards reader at Coventry University, called Leighton Buzzard’s tremors “very, very strange”.
“What appears to have happened is this was an initial earthquake in a hidden fault, caused by some stress or whatever,” said Dr. Blackett.
“These next two events are a readjustment of the fault lines to return to some sort of stability.
“The crust has to adjust to become stable again, seems to have happened to the poor people of Leighton Buzzard.”
How many earthquakes have there been in the UK and how often do they occur?
Most earthquakes in the UK are so small they can’t be felt, because the UK isn’t on a fault line between tectonic plates.
According to data from the British Geological Survey, between 20 and 30 earthquakes are felt in the UK each year, with hundreds of smaller earthquakes recorded by sensitive instruments.
In the 50 days up to 22 September, for example, a total of 39 earthquakes were recorded in Great Britain.
These ranged from minus 0.1 on the Richter scale to Tuesday’s peak of 3.0, including a 1.0 tremor near central Bristol on 4 September. Many tremors occur off the coast.
The Richter scale is the globally recognized numerical scale for measuring seismograph wobble, and destructive earthquakes typically measure above 5.5.
The British Geological Survey said: ‘A magnitude 4 earthquake occurs in Britain approximately every two years. We experience a magnitude 5 roughly every 10-20 years. Research suggests that the largest possible earthquake in the UK is around 6.5″.
The corps scientists added: ‘The driving forces for seismic activity in the UK are unclear; however they include regional compression caused by the movement of the Earth’s tectonic plates and uplift resulting from the melting of the ice sheets that covered many parts of Great Britain thousands of years ago.
What has been the largest earthquake so far?
The largest known British earthquake occurred near Dogger Bank in 1931, with a magnitude of 6.1.
Fortunately, it was 60 miles offshore, but still powerful enough to cause minor damage to buildings on the east coast of England.
The UK’s most damaging earthquake occurred in the Colchester area in 1884. Around 1200 buildings needed repairs, chimneys collapsed and walls were cracked.
The last major earthquake, measuring 5.2, hit Market Rasen in Lincolnshire in 2008 and was felt as far away as Newcastle and London.
Where else in Europe is earthquake-prone?
Several areas in the Mediterranean region experienced severe earthquakes.
Italy is the most earthquake-prone European country, with the Eurasian and African tectonic plates shifting about 4-10 mm per year under its southern half.
These plates are not only responsible for some of the deadliest earthquakes in Europe, but also for the famous Italian volcanoes: Vesuvius, Etna and Stromboli.
The last major earthquake to hit Italy was on August 24, 2016, when quakes measuring 6.2 shook towns and villages 65 miles northeast of Rome in the early morning hours.
It claimed 297 lives and devastated the towns of Amatrice and Arquata del Tronto in particular, with nearly 4,000 people left homeless by the destruction.
Dozens were feared dead in January 2017 after a series of four earthquakes, the strongest measuring 5.3, shook buildings in Florence and Rome and triggered an avalanche that swept over the Hotel Rigopiano, in Abruzzo.
The deadliest documented earthquake in Europe was on December 28, 1908, when a magnitude 7.0 earthquake in the Strait of Messina between Sicily and mainland Italy killed 72,000.
“The highest seismicity is concentrated in the central-southern part of the peninsula, along the Apennine ridge, in Calabria and Sicily and in some northern areas, such as Friuli, part of Veneto and western Liguria”, explains the Civil Protection Department.
The US Geological Survey adds: “The region’s tectonic activity cannot be explained simply by the collision of the Eurasian and African plates. It has been suggested that deeper lithospheric processes are controlling some of the deformation observed at the surface.”
Spain, France, Greece and Portugal have also suffered terrible earthquakes in the last three centuries.
The most recent was in May 2011, when at least eight people died when a magnitude 5.1 earthquake shook southern Spain under the province of Granada.