Thousands woke to a terrifying sound and rushed from their homes in their nightclothes – later the full realisation of what had happened emerged and scientists flocked to Wales to investigate
On a brilliant, sunny summer’s morning, a deafening rumble that intensified with each passing moment woke thousands of residents in part of Wales. People rushed into the streets, some still wearing their nightwear, fearing one of the local nuclear power stations had exploded
It was shortly before 8am on July 19, 1984, when the realisation dawned that Wales was neither under attack nor facing nuclear catastrophe, but rather at the heart of a massive earthquake, at least by northern European standards.
Registering 5.4 on the Richter scale, it persisted for 12 seconds and the British Geological Survey (BGS) subsequently confirmed it as the largest onshore earthquake in the UK during the 20th century. Always keep on top of the latest Welsh news with our newsletter
Centred on Llithfaen, on the Llyn peninsula, it was experienced across an area of approximately 250,000 square kilometres, reports North Wales Live.
A BGS spokesman remarked at the time: “Most of the UK would have felt it to a degree, right up to Edinburgh. They happen very rarely.”
Following the tremors, electricity supplies were severed across substantial portions of Gwynedd. Meanwhile, livestock bolted in panic and dry stone walls crumbled. Ensure our latest news and sport headlines always appear at the top of your Google Search by making us a Preferred Source. Click here to activate or add us as Preferred Source in your Google search settings
The gable end of a property near Aberdaron gave way and the exterior walls of another in the vicinity began bulging outwards. A fissure emerged in the spire of a chapel in Pwllheli and chimney stacks tumbled across a widespread area.
Data collected from 7,000 BGS questionnaires distributed in the Gwynedd region revealed that many individuals had clung to furniture for stability, pictures and mirrors were jostled against walls, hefty furniture shifted and water sloshed from fish tanks.
One father mistook the tremors for his 15-month-old son, asleep in his room, rattling his cot against the wall. He reprimanded him to cease, only realising the true nature of the situation later on.
Seismologists hurried to Gwynedd to witness the anticipated aftershocks which persisted for several months. The experts debated amongst themselves whether these tremors were aftershocks or distinct earthquakes.
One registered 4.3 on the Richter scale.
Conceived by American geologist Charles Francis Richter, the scale quantifies the magnitude of earthquakes on a logarithmic scale, meaning a quake of magnitude 5 is ten times more potent than one of magnitude 4.
North west Wales is a hub of seismological activity, a phenomenon that has long baffled experts given the area’s location away from major tectonic plate junctions.
Amateur geologist Donald Pritchard, former headmaster at Ysgol Penysarn near Amlwch, proposed his own theory regarding the cause of this tremor, as well as previous ones.
“I believe that it was caused by a geological fault known as the Berw Fault, which runs almost parallel with the Menai Strait, from Pentraeth through Pentre Berw and Llangaffo to the coast.
“It’s a geological feature that has been known about for a long time, although perhaps it’s not as famous as the San Andreas Fault! But Greenly described it at length in his book, Geology of Anglesey, published early this century.
“It’s where two different rock strata meet, 17.3km beneath the surface, and is responsible for the rocky outcrops which can be seen on the surface all along its line,” he said.
Only one earthquake more powerful than the Llithfaen one has ever been scientifically recorded in the UK, one of magnitude 6.1 that struck off the east coast of Essex in 1931.
Earthquakes usually cause little damage in northern Europe, but ones of similar magnitude have been known to wreak havoc in other parts of the world.
According to the United Nations there were 1,564 earthquakes of magnitude 5 or higher across the globe last year.
The most potent tremor was an earthquake measured at 8.2 on the Richter scale that hit parts of western Mexico last September, causing widespread damage and 98 fatalities. A second earthquake, at 7.1, struck the country’s capital city two weeks later, resulting in 370 deaths.
However, the deadliest was one at 7.3 which struck the Iran/Iraq border region on November 12, claiming 630 lives.