1990 Bishop's Castle earthquake
Encyclopedia
The 1990 Bishop's Castle earthquake was an earthquake
that hit near the town of Bishop's Castle
, Shropshire
, England
on 2 April 1990.
and Wales
at 13:46 34.2s UTC. Early news reports in the immediate aftermath speculatively attributed the epicentre to places as far apart as Nottingham
and a valley in the east of Wales
and then settled on Wrexham
, before geologists finally concluded that it had in fact been in the vicinity of the small town of Clun
near the town of Bishop's Castle
, Shropshire
.
Middle Lias
.
. Its final estimated magnitude was 5.1, which meant that it was the strongest earthquake to have struck the UK since the 1984 Lleyn Peninsula earthquake
.
to the south-west.
In Shrewsbury
, the county town of Shropshire
, which lies some miles to the north of Bishop's Castle
, there was damage to masonry, with a number of chimney stacks being broken off from roofs and collapsing partially or completely into gardens and streets. Some others were knocked askew. Several of the worst affected buildings, including shops, were evacuated. Police cordons were put up around houses at risk of chimney-collapse until they had been made safe, with at least fifty properties in the town reported as requiring emergency attention within the twenty-four hours immediately following the event, while others requiring less urgent treatment were tended to on subsequent days.
There was also damage to ornamental features such as crosses and gargoyles built into the masonry of some of Shrewsbury
's medieval churches, and to Clun Castle
.
Electrical power was lost from areas served by some substations situated approximately thirty kilometres (seventeen miles) from the epicentre after the earthquake caused transformers at the substations to trip offline.
Residents of the worst affected areas, including parts of Shrewsbury
, reported lateral shaking and swaying to the walls of their houses at the height of the tremor, which was preceded and then accompanied by a rumbling noise that gained strength over a period of 15 to 30 seconds before reaching and sustaining peak intensity during the most severe shaking. Finally, the movement and accompanying sound tailed off much more rapidly than it had first built up, stopping altogether within just a few seconds from the peak activity.
Damage to buildings was also reported in Wrexham
, and some minor damage as far north as Liverpool
and Manchester
.
No serious injuries were reported.
An engineering consultant, using the 1990 Bishop's Castle earthquake specifications as a model, has estimated that a slightly weaker earthquake measuring 4.8 on the Richter scale
which struck at Dudley
in September 2002 would have caused structural damage of an order costing less than 5% of the cost of the complete reconstruction of an entire property to repair, to 1% of buildings situated in towns in the vicinity of the epicentre. While some indication of the typical percentage of homes damaged to a similarly minor extent by a slightly stronger earthquake measuring 5.1 on the Richter scale
may be extrapolated from this estimation, a representative of the British Geological Survey
has stated that 'numerous' but fewer than 20% of properties in Shrewsbury suffered the partial or total loss of their chimneys or damage of equivalent gravity (see below). Reliable, exact figures of the percentage of buildings damaged close to the epicentre of the 1990 Bishop's Castle earthquake are not readily available, but the aforesaid sources taken together appear clearly to indicate that between 1% and 20% of properties in towns near the epicentre suffered damage of European Macroseismic Scale
Grade 7 severity.
The Welsh Borders suffer frequent earthquakes by British standards. Over the last century, there have been sizeable shocks near Shrewsbury in 1932, near Ludlow in 1926 and near Hereford in 1896 and 1924.
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
that hit near the town of Bishop's Castle
Bishop's Castle
Bishop's Castle is a small market town in Shropshire, England, and formerly its smallest borough. According to the 2001 census it had a population of 1,630. Bishop's Castle is east of the Wales-England border, about north-west of Ludlow and about south-west of Shrewsbury. To the south is Clun...
, Shropshire
Shropshire
Shropshire is a county in the West Midlands region of England. For Eurostat purposes, the county is a NUTS 3 region and is one of four counties or unitary districts that comprise the "Shropshire and Staffordshire" NUTS 2 region. It borders Wales to the west...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
on 2 April 1990.
Location, date and time
On April 2, 1990, a powerful earth tremor was felt across much of EnglandEngland
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
and Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
at 13:46 34.2s UTC. Early news reports in the immediate aftermath speculatively attributed the epicentre to places as far apart as Nottingham
Nottingham
Nottingham is a city and unitary authority in the East Midlands of England. It is located in the ceremonial county of Nottinghamshire and represents one of eight members of the English Core Cities Group...
and a valley in the east of Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
and then settled on Wrexham
Wrexham
Wrexham is a town in Wales. It is the administrative centre of the wider Wrexham County Borough, and the largest town in North Wales, located in the east of the region. It is situated between the Welsh mountains and the lower Dee Valley close to the border with Cheshire, England...
, before geologists finally concluded that it had in fact been in the vicinity of the small town of Clun
Clun
Clun is a small town in Shropshire, England. The town is located entirely in the Shropshire Hills Area of Outstanding Natural Beauty. The 2001 census recorded 642 people living in the town...
near the town of Bishop's Castle
Bishop's Castle
Bishop's Castle is a small market town in Shropshire, England, and formerly its smallest borough. According to the 2001 census it had a population of 1,630. Bishop's Castle is east of the Wales-England border, about north-west of Ludlow and about south-west of Shrewsbury. To the south is Clun...
, Shropshire
Shropshire
Shropshire is a county in the West Midlands region of England. For Eurostat purposes, the county is a NUTS 3 region and is one of four counties or unitary districts that comprise the "Shropshire and Staffordshire" NUTS 2 region. It borders Wales to the west...
.
Cause
Bishops Castle lies atop an ancient geological fault line - the Pontesford Linley fault. A sudden movement in the fault sent shock waves through the rock. The local rocks are predominantly JurassicJurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
Middle Lias
Early Jurassic
The Early Jurassic epoch is the earliest of three epochs of the Jurassic period...
.
Magnitude
The magnitude of the earthquake was originally measured as being between 4.9 and 5.4 on the Richter scaleRichter magnitude scale
The expression Richter magnitude scale refers to a number of ways to assign a single number to quantify the energy contained in an earthquake....
. Its final estimated magnitude was 5.1, which meant that it was the strongest earthquake to have struck the UK since the 1984 Lleyn Peninsula earthquake
1984 Lleyn Peninsula earthquake
The 1984 Llŷn Peninsula earthquake struck the Llŷn Peninsula in Gwynedd, north-west Wales on 19 July 1984 at 06:56 UTC . It measured 5.4 on the Richter scale, and is the largest known onshore earthquake to occur in the UK since instrumental measurements began. The effects were felt throughout...
.
Impact
The earthquake was felt by people as far away as the east of the Republic of Ireland to the west, the city of Newcastle Upon Tyne to the north-east, the county of Kent to the south-east, and the county of CornwallCornwall
Cornwall is a unitary authority and ceremonial county of England, within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall has a population of , and covers an area of...
to the south-west.
In Shrewsbury
Shrewsbury
Shrewsbury is the county town of Shropshire, in the West Midlands region of England. Lying on the River Severn, it is a civil parish home to some 70,000 inhabitants, and is the primary settlement and headquarters of Shropshire Council...
, the county town of Shropshire
Shropshire
Shropshire is a county in the West Midlands region of England. For Eurostat purposes, the county is a NUTS 3 region and is one of four counties or unitary districts that comprise the "Shropshire and Staffordshire" NUTS 2 region. It borders Wales to the west...
, which lies some miles to the north of Bishop's Castle
Bishop's Castle
Bishop's Castle is a small market town in Shropshire, England, and formerly its smallest borough. According to the 2001 census it had a population of 1,630. Bishop's Castle is east of the Wales-England border, about north-west of Ludlow and about south-west of Shrewsbury. To the south is Clun...
, there was damage to masonry, with a number of chimney stacks being broken off from roofs and collapsing partially or completely into gardens and streets. Some others were knocked askew. Several of the worst affected buildings, including shops, were evacuated. Police cordons were put up around houses at risk of chimney-collapse until they had been made safe, with at least fifty properties in the town reported as requiring emergency attention within the twenty-four hours immediately following the event, while others requiring less urgent treatment were tended to on subsequent days.
There was also damage to ornamental features such as crosses and gargoyles built into the masonry of some of Shrewsbury
Shrewsbury
Shrewsbury is the county town of Shropshire, in the West Midlands region of England. Lying on the River Severn, it is a civil parish home to some 70,000 inhabitants, and is the primary settlement and headquarters of Shropshire Council...
's medieval churches, and to Clun Castle
Clun Castle
Clun Castle is a ruined castle in the small town of Clun, Shropshire. Clun Castle was established by the Norman lord Robert de Say after the invasion and went on to become an important Marcher lord castle in the 12th century, with an extensive castle-guard system...
.
Electrical power was lost from areas served by some substations situated approximately thirty kilometres (seventeen miles) from the epicentre after the earthquake caused transformers at the substations to trip offline.
Residents of the worst affected areas, including parts of Shrewsbury
Shrewsbury
Shrewsbury is the county town of Shropshire, in the West Midlands region of England. Lying on the River Severn, it is a civil parish home to some 70,000 inhabitants, and is the primary settlement and headquarters of Shropshire Council...
, reported lateral shaking and swaying to the walls of their houses at the height of the tremor, which was preceded and then accompanied by a rumbling noise that gained strength over a period of 15 to 30 seconds before reaching and sustaining peak intensity during the most severe shaking. Finally, the movement and accompanying sound tailed off much more rapidly than it had first built up, stopping altogether within just a few seconds from the peak activity.
Damage to buildings was also reported in Wrexham
Wrexham
Wrexham is a town in Wales. It is the administrative centre of the wider Wrexham County Borough, and the largest town in North Wales, located in the east of the region. It is situated between the Welsh mountains and the lower Dee Valley close to the border with Cheshire, England...
, and some minor damage as far north as Liverpool
Liverpool
Liverpool is a city and metropolitan borough of Merseyside, England, along the eastern side of the Mersey Estuary. It was founded as a borough in 1207 and was granted city status in 1880...
and Manchester
Manchester
Manchester is a city and metropolitan borough in Greater Manchester, England. According to the Office for National Statistics, the 2010 mid-year population estimate for Manchester was 498,800. Manchester lies within one of the UK's largest metropolitan areas, the metropolitan county of Greater...
.
No serious injuries were reported.
An engineering consultant, using the 1990 Bishop's Castle earthquake specifications as a model, has estimated that a slightly weaker earthquake measuring 4.8 on the Richter scale
Richter magnitude scale
The expression Richter magnitude scale refers to a number of ways to assign a single number to quantify the energy contained in an earthquake....
which struck at Dudley
Dudley
Dudley is a large town in the West Midlands county of England. At the 2001 census , the Dudley Urban Sub Area had a population of 194,919, making it the 26th largest settlement in England, the second largest town in the United Kingdom behind Reading, and the largest settlement in the UK without...
in September 2002 would have caused structural damage of an order costing less than 5% of the cost of the complete reconstruction of an entire property to repair, to 1% of buildings situated in towns in the vicinity of the epicentre. While some indication of the typical percentage of homes damaged to a similarly minor extent by a slightly stronger earthquake measuring 5.1 on the Richter scale
Richter magnitude scale
The expression Richter magnitude scale refers to a number of ways to assign a single number to quantify the energy contained in an earthquake....
may be extrapolated from this estimation, a representative of the British Geological Survey
British Geological Survey
The British Geological Survey is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. The BGS headquarters are in Keyworth, Nottinghamshire, but other centres...
has stated that 'numerous' but fewer than 20% of properties in Shrewsbury suffered the partial or total loss of their chimneys or damage of equivalent gravity (see below). Reliable, exact figures of the percentage of buildings damaged close to the epicentre of the 1990 Bishop's Castle earthquake are not readily available, but the aforesaid sources taken together appear clearly to indicate that between 1% and 20% of properties in towns near the epicentre suffered damage of European Macroseismic Scale
European Macroseismic Scale
The European Macroseismic Scale is the basis for evaluation of seismic intensity in European countries and is also used in a number of countries outside Europe...
Grade 7 severity.
The Welsh Borders suffer frequent earthquakes by British standards. Over the last century, there have been sizeable shocks near Shrewsbury in 1932, near Ludlow in 1926 and near Hereford in 1896 and 1924.