Tuesday 26 August 2014

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 Summertime (slightly after 9.30 pm GMT) on Monday 18 August 2014. This was not a large event, and there was no danger of any damage or injuries, though it was felt in Porthmadog.

The approximate location of the 18 August 2014 Gwynedd 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...

The British Geological Survey recorded a Magnitude 0.9 Earthquake at a depth of 11 km in eastern Gwynedd...

The British Geological Survey recorded a Magnitude 1.0 Earthquake at a depth of 7 km about a kilometer to the...

A series of three minor Earthquakes happened roughly 2 km off the northeast coast of the Lleyn Peninsula in northwest Wales on the evening of Wednesday 26 June 2013, according to the British Geological Survey. The quakes took place over a period of about two and a half minutes at about 11.30 British Summertime (10.30...

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