Although not competing with areas famous for their instability such as western California, Japan or Sumatra, Wales is a region of regular active Earth movements. You might be surprised to learn that at least sixteen significant earthquakes have occurred in Wales during the last century.

Seismograph showing an earthquake in north Wales in 1994

Why do earthquakes occur in Wales?

The British Geological Survey (BGS) records around 300-400 earthquakes each year in Britain. Wales, along with the rest of the UK, sits on the European plate, and stress builds up as it is pushed slowly north-eastwards from the Mid-Atlantic Ridge. The stress is released by movement along pre-existing fault planes, causing an earthquake.

Where do earthquakes occur in Wales?

There are several long-active fault systems in Wales. Once faults form, they create weak zones in the crust that can be reactivated time and time again. For example, the fault system running parallel to the Menai Strait between Anglesey and Bangor in north Wales are known to have been active over 500 million years ago and have also been the sites of more recent earthquakes.

The Menai Strait area is the most seismically active area in Wales and one of the most active in the UK. The last major earthquake occurred here in 1984, but many others are known from historical records (including 1827, 1842, 1852, 1874, 1879, 1903). Although many events have been recorded in south Wales, from Pembroke to Newport, only the Swansea area shows consistent activity, with significant earthquakes occurring in 1727, 1775, 1832, 1868 and 1906.

Largest earthquake in Wales for 100 years

The 1984, magnitude 5.4, Menai Strait earthquake was the largest onshore UK event for over 100 years. The epicentre was located in northern Llŷn, north Wales and the quake originated at a depth of approximately 22 km in the Earth's crust.

Another major UK earthquake occurred on 2 April 1990 in the Welsh Borders. This magnitude 5.1 event was felt over an area of approximately 140,000 square kilometres and was followed by six aftershocks. The epicentre was initially identified as being at Bishop's Castle in Shropshire, but this was later revised to a location just inside the Welsh border (latitude 52.43°' N, longitude 3.03° W).

Local damage

In both earthquakes the damage was relatively minor, including cracks in plaster and masonry and collapse of chimneys. In the Bishop's Castle event this was limited to the area immediately around the epicentre.

The only fatality known from any seismic activity in Wales is from a woman falling down the stairs and being killed during the Porthmadog earthquake of 1940.

Recent activity

An earthquake with a magnitude of 4.6 occurred in south Wales on February 17, 2018. According to the British Geological Survey (BGS), its epicentre was between Ystradgynlais and Ystalafera. A Welsh earthquake also occurred in the Bristol Channel on 20th February 2014, and was widely felt across South Wales, Devon, Somerset and western Gloucestershire. The BGS received several reports from the media and local residents describing “felt like the vibration of a large vehicle passing the building”, “the whole house seemed to move/wobble back and forth a few times”..

The magnitude 4.1 earthquake is the largest to hit South Wales since 2013.

Other recent earthquake activity from Wales include:

• A magnitude 3.8 earthquake on the Lleyn Peninsula on 29th May 2013.
• Magnitude 2.9 earthquake near Nantyffyllon on 5th June 2009.
• Magnitude 2.9 earthquake near Llangollen on 30th November 2007
• A magnitude 2.9 quake in Cardiff on 20th June 2002.

In general, humans cannot feel events of less than magnitude 2.

Recording earthqake activity at Amgueddfa Cymru.

A seismograph at National Museum Cardiff displays output from a local seismometer and allows observation of data from seismic events.

As seismometers are very sensitive to all types of ground vibrations, not only earthquakes but local traffic, trains and even roadworks, it was not possible to locate a seismometer in Cardiff city centre. Instead, data is obtained by a radio link from the nearest BGS seismometer near Newport, Gwent.

A selection of images from St Teilo's Church

Decoration

The screen from the west door.

The carpenter’s signature, and the date the church was opened. It reads ‘XIIII Oct A.D. MMVII RJS fecit’. Translated from Latin, this means ‘14 October 2007 A.D. RJS (Ray J. Smith) made this’.

This is a collection of all the so-called 'Passion', or Easter symbols. They tell the story of Jesus Christ's crucifixion, showing only the tools used.

Aspects of daily life were reflected everywhere in this building in Tudor times. In our interpretation, we have added some local characters of our own. Here's Ray, the carpenter, again, surrounded by his tools!

This is also a corrupted Pagan symbol. The hare, as symbol of fertility, is turned into a Trinity symbol. Their ears are all joined and the simple hare becomes a symbol of resurrection.

Worshipper's lives in Tudor times were strongly linked to the natural world. As a consequence, symbols like the green man — the Pagan spirit of the forest — were acceptable in church.

In the same way medieval church had many different functions, it also had many different messages and symbols conveyed through the building. This is a royal symbol, the Tudor Rose, bringing together the York and Lancaster roses.

The apostles were painted by an artist called Fleur Kelly. She worked with our own historic painters to decorate the rest of the screen. The three saints hold an object in their hands, so that we can tell who they are.

Philip was crucified for his beliefs, so he holds a cross. John was made to drink poisoned wine — and lived — so he holds a cup with a snake in it. Peter holds the keys to the gates of heaven, so he holds a key.

Teilo's life is depicted in great detail on the loft. You can view it in full by clicking

here

.

This panel shows the story of Teilo escaping from hounds, after trying to establish a community on the Count's land in Dol, Brittany.

A closer view shows us how much is displayed on the Loft, too. Here are four of the twelve Apostles — Saints held in special view by Christians for their work spreading Jesus' message. Underneath is Teilo's life story, carved into oak.

A closer look at the screen and loft. These fixtures would have been common all over Wales and England until the mid 16th century. The screen was built to separate the ordinary people from the priests who held the service. The loft on top was used for display, rather than as a minstrel's gallery or choir loft.

Here's Ray Smith, Head Carpenter at our Historic Buildings unit, standing in front of the screen he made. The tools in his hand are what were used to make it — a hammer and chisels.

Post War miner shortage

Group of Slovenians at Oakdale Training Centre 1948.

Following the Second World War, the demand for coal was high and generally rising. Post-war recovery and growth demanded cheap and abundant energy that could only come from coal. There was an urgent need to recruit more miners. One source for these was among the thousands of Europeans who had to flee their home countries during the War.

Although Britain desperately needed these men they were not always welcomed with open arms and there was much resistance from local National Union of Mineworkers' lodges. There was more disquiet when the recruitment of Italians began in 1951, and things were no better when the National Coal Board tried to recruit among Hungarian refugees after the 1956 revolution. By this time another group had already entered the coal field. In 1954 the German mining engineering group, Thyssen UK, came to work in south Wales, bringing some of their own countrymen with them.

As with today's immigrants, these 'foreign workers' faced much initial suspicion, which arose partly from ignorance and partly from the fear of unemployment among the local population. These young men came to Britain after years of hardship, danger and tragedy.

"All Poles"

Nyk Woszczycki (2nd from left) in a group celebrating his friend Joe Hughes's retirement from Britannia Colliery

Many left the coal industry as soon as they could, many even left Britain, but the ones who stayed earned a lasting reputation for toughness and hard work. Even though they came from many countries they tend to be regarded as 'all Poles' by the Welsh miner. They married local girls and settled down; on their living room walls can often be found photographs of their children and grandchildren, who have been brought up as Welsh. Many of these have gained university degrees; some have won sporting honours for Wales.

In spite of their pride in their original homelands, most now regard themselves as Welsh. In turn, Wales should be proud of them and the part they have played in her history.

This article forms part of a magazine in the series 'Glo' produced by Big Pit National Coal Museum. Download the complete magazine here:

A scan from the seismograph at National Museum Cardiff showing the Market Rasen earthquake on 27 February 2008 at 00:57.14 GMT. The shock waves were recorded by a seismometer located near Newport, south Wales, and transmitted to the seismograph at the Museum.

The earthquake was recorded by the Museum's seismograph at 00:57.14 GMT 27 February. This has been identified as the Magnitude 5.2 earthquake detected by the British Geological Survey. The epicentre was initially reported as located just north of Market Rasen, Lincolnshire, at 00:56.47 GMT.

The earthquake waves took just 27 seconds to travel the 158 miles between Market Rasen and the Museum's seismometer near Newport, south Wales. This means that the earthquake's waves were travelling at approximately 5.85 miles per second.

This is the largest onshore event in the UK since the Magnitude 5.1 earthquake at Bishops Castle in the Welsh Borderland on 2 April 1990.

The Market Rasen event was felt by people as far afield as Newcastle, Yorkshire, London, Cumbria, the Midlands, Norfolk and parts of Wales. Damage to roofs, walls and chimneys around the epicentre area were reported and one person was injured in Wombwell near Barnsley, South Yorkshire as a result of falling masonry.

Aftershock

Earthquakes of this size are typically followed by smaller earthquakes or 'aftershocks'. A magnitude 1.8 earthquake was recorded in the region just a few hours after the main event.

A detailed investigation is required to establish the geological structure responsible for the main earthquake. The Geological Survey has already calculated that the quake occurred at a depth of around 18km. This suggests it most likely occurred along an ancient fault in Precambrian rocks, such as those that underlie much of Wales.

The exact fault along which the quake occurred is unlikely to be exposed at the surface as younger Palaeozoic and Mesozoic rocks (Carboniferous, Permian, Triassic and Jurassic, for example) overlie the Precambrian rocks in the Market Rasen area.

The magnitude 5.4 Lleyn Peninsula earthquake of 19 July 1984 remains the largest recorded onshore earthquake in the UK.

Information from:

• http://www.earthquakes.bgs.ac.uk/
• http://www.emsc-csem.org/
• http://earthquake.usgs.gov/regional/neic/
• http://news.bbc.co.uk/