Questions remain four decades after town’s earthquake
WHILE Widnes is associated with many things, earthquakes isn’t one of them.
That’s why it is still a shock - no pun intended - to see the town on the British Geological Survey’s list of significant British earthquakes, dating from November 3, 1976.
At just before 10am on that Wednesday morning, the town was shaken by a disturbance 2km underground that registered at 4.5 on the Richter scale of local magnitude, the rough equivalent of around 500-1,000 tons of TNT explosive going off.
People still remember it now, more than 43 years on.
However, an expert on seismic events does not believe it was an earthquake at all.
Dr Roger Musson is a research associate with the British Geological Survey, specialising in historical earthquakes in Britain.
He investigated the Widnes quake in the early 1980s as part of his 40-year career.
Dr Musson said: “I gathered a lot of newspapers and so on, and there were reports of tall buildings
● being shaken and people rushing into the streets.
“A magnitude of 4.5 puts Widnes into the significant category too, but although I can’t prove it, I don’t think it was an earthquake.
“I believe it was caused by the collapse of old salt workings underground.”
Dr Musson, 66, explained there is a close relationship between the magnitude of an earthquake and the area where the shock is felt.
“A 4.5 earthquake in Widnes should have been felt over most of England and Wales, but it wasn’t,” he said. “Instead it was mainly felt around Merseyside.
“Another piece of evidence reported at the time was a depression in the ground appeared at Widnes.
“The depression and the limited area are both related to collapses from old salt mines, which typically leave large voids behind and can set off seismometers when they happen. A collapse of a normal mine working would be far smaller.
“However that is just my belief. I cannot prove it, so Widnes remains on the list.”
The quake - or collapse - also remains fresh in people’s minds. On the Widnes Past And Present Facebook group, Elain
Andrews said she was in the Municipal Building in Widnes and thought it was going to collapse.
Nita White said: “I remember it. I was working at the shirt factory and all our trolleys moved down the factory.”
Sylvia Farmer said: “I remember being in hospital after my second child and it set all the fire alarms off. We had to stay on the wards with the fire doors shut.”
Jean Alice remembered: “I remember washing the dishes and the water in the sink swayed. I thought l had gone dizzy until my son who was sat on the floor said ‘the floor is moving’.”
Dr Musson said reactions like that are typical for earthquakes of around 4.5 magnitude.
He added the strongest ever recorded in the UK was in 1931 in the North Sea, which reached level six on the Richter scale.
“That may not sound like much of a difference, but the scale goes up in steps of 30,” he explained. “So level seven is 30 times more powerful than level six, and level eight is 900 times more powerful than level six.
“We are lucky in the UK as earthquakes happen at the edges of tectonic plates and we are in the middle of one.
“The nearest seismically active plate edge is in Italy and Greece. Seismologists wouldn’t get out of bed for anything less than a level six. Hotspots are also around the edge of the Pacific Ocean, the socalled Ring Of Fire, which includes Siberia, the Philippines, Japan and the west coast of the US.”
Dr Musson said while you can’t predict earthquakes, you can work out the ‘average recurrence rate’.
“We can say that on average you will get an earthquake of this magnitude every five or 10 years for instance, which engineers can then factor into building design and so on.”
So people in Widnes shouldn’t worry about another earthquake rocking the town?
“I shouldn’t think so, no.”