Magnitude 1.2 Earthquake on the Lleyn Peninsula.

The British Geological Survey recorded a Magnitude 1.3 Earthquake at a depth of 10 km, on the north coast of the Lleyn Peninsula in Gwynedd, North Wales, slightly after 8.05 am British Summertime (slightly after 9.05 am GMT) on Tuesday 11 August 2015. An Earthquake of this size is not dangerous, and is highly unlikely to have caused any damage or injuries, but may have been felt locally.

The approximate location of the 11 August 2015 Lleyn Peninsula Earthquake. Google Maps.

Earthquakes become more common as you travel north and west in Great Britain, with the west coast of Scotland being the most quake-prone part of the island and the northwest of Wales being more prone  to quakes than the rest of Wales or most of England.

The precise cause of Earthquakes in the UK can be hard to determine; the country is not close to any obvious single cause of such activity such as a plate margin, but is subject to tectonic pressures from several different sources, with most quakes probably being the result of the interplay between these forces.

Britain is being pushed to the east by the expansion of the Atlantic Ocean and to the north by the impact of Africa into Europe from the south. It is also affected by lesser areas of tectonic spreading beneath the North Sea, Rhine Valley and Bay of Biscay. Finally the country is subject to glacial rebound; until about 10 000 years ago much of the north of the country was covered by a thick layer of glacial ice (this is believed to have been thickest on the west coast of Scotland), pushing the rocks of the British lithosphere down into the underlying mantle. This ice is now gone, and the rocks are springing (slowly) back into their original position, causing the occasional Earthquake in the process. 

(Top) Simplified diagram showing principle of glacial rebound. Wikipedia. (Bottom) Map showing the rate of glacial rebound in various parts of the UK. Note that some parts of England and Wales show negative values, these areas are being pushed down slightly by uplift in Scotland, as the entire landmass is quite rigid and acts a bit like a see-saw. Climate North East.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. If you felt this quake, or were in the area but did not (which is also useful information) then you can report it to the British Geological Survey here.

See also...

Magnitude 3.0 Earthquake off the coast of Caernarfon, North Wales.

The British Geological Survey recorded a Magnitude 3.0 Earthquake at a depth of 9 km, off the east coast of Caernarfon in Gwynedd, North Wales, slightly after...

Magnitude 1.0 Earthquake in Gwynedd, North Wales.

The British Geological Survey recorded a Magnitude 1.0 Earthquake at a depth of 12 km in northeast Gwynedd, North Wales, slightly after 10.30 pm British...

Magnitude 0.9 Earthquake in Gwynedd, North Wales.

The British Geological Survey recorded a Magnitude 0.9 Earthquake at a depth of 11 km in eastern Gwynedd County, North Wales, slightly before 1.25 am GMT...

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Magnitude 3.8 Earthquake off the Lleyn Peninsula, North Wales.

A magnitude 3.8 Earthquake at a depth of 8 km occurred off the coast of the Lleyn Peninsula in North Wales, slightly after 4.15 am British Summertime (slightly after 3.15 am GMT) on Wednesday 29 May 2013, according to the British Geological Survey. While this is not a large Earthquake and is unlikely to have caused any damage or injuries, it is exceptionally large for Wales, and was felt as far away as Southport in Lancashire, with many people on the Peninsula reporting being waken by the quake and hearing a loud rumbling noise that went on for about 30 seconds.

Map showing the location of the 29 May 2013 Earthquake, and places where people reported feeling the quake. British Geological Survey.

Earthquakes become more common as you travel north and west in Great Britain, with the west coast of Scotland being the most quake-prone part of the island and the northwest of Wales being more prone  to quakes than the rest of Wales or most of England.

The precise cause of Earthquakes in the UK can be hard to determine; the country is not close to any obvious single cause of such activity such as a plate margin, but is subject to tectonic pressures from several different sources, with most quakes probably being the result of the interplay between these forces.

Britain is being pushed to the east by the expansion of the Atlantic Ocean and to the north by the impact of Africa into Europe from the south. It is also affected by lesser areas of tectonic spreading beneath the North Sea, Rhine Valley and Bay of Biscay. Finally the country is subject to glacial rebound; until about 10 000 years ago much of the north of the country was covered by a thick layer of glacial ice (this is believed to have been thickest on the west coast of Scotland), pushing the rocks of the British lithosphere down into the underlying mantle. This ice is now gone, and the rocks are springing (slowly) back into their original position, causing the occasional Earthquake in the process. 

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. If you felt this quake, or were in the area but did not (which is also useful information) then you can report it to the British Geological Survey here.

See also Earthquake under the Lleyn Peninsula, Earthquake in Carmarthenshire, Earthquake in Snowdonia National Park, Friday 27 April 2012, Earthquake beneath Barmouth, Gwynedd, northwest Wales and River Neath turned orange by mining run-off.

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Earthquake under the Lleyn Peninsula.

On Friday 22 March 2013, slightly before 1.00 pm, GMT, the British Geological Survey recorded a Magnitude 2.2 Earthquake at a depth of 12 km beneath the Lleyn Peninsula in North Wales, roughly 20 km west of Porthmadog. This is not a large Earthquake, and occuring at this depth in a fairly remote location, it is quite likely that this event was not witnessed by anyone, and it is highly unlikely to have caused any damage or injuries.

The location of the 22 March Earthquake. Google Maps.

Small Earthquakes are not uncommon in the UK, though more serious events are rare; there has only ever been one recorded Earthquake-related death in Wales, in 1940, when an elderly woman fell down a flight of stairs in Porthmadog.

The precise cause of Earthquakes in the UK can be hard to determine, with most probably being the result of the interplay of more than one source of tectonic stress. The UK is being pushed to the east by the expansion of the Atlantic Ocean (allong with the rest of Eurasia) and to the north by the impact of Africa into Europe from the south. It is also affected by lesser spreading centers beneath the North Sea, Rhine Valley and Bay of Bicay. Finally it is subject to glacial rebound; until about 10 000 years ago much of the north of the country was covered by a thick layer of glacial ice, pushing the rocks of the British lithosphere down into the underlying mantle. These rocks are now rebounding (slowly) into place, causing the occational Earthquake in the process. This is particularly true in the north and west of the country, with Earthquakes being most common on the west coast of Scotland.

Witness accounts can help geologists to understand Earthquakes and the geological processes that cause them. If you felt this quake, or if you were in the area but did not (which is also useful information) then you can report it to the British Geological Survey here.

See also Earthquake in Carmarthenshire, Earthquake in Snowdonia National Park, Friday 27 April 2012, Earthquake beneath Barmouth, Gwynedd, northwest Wales and Earthquakes on Sciency Thoughts YouTube.

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