Friday 5 December 2014

Magnitude 2.0 Earthquake in Midlothian, Scotland.

The British Geological Survey recorded a Magnitude 2.0 Earthquake at a depth of 6 km in southwest Midlothian, Scotland, about 10 knm to the south of Edinburgh, slightly before 10.00 pm GMT on Wednesday 3 December 2014. This is a small event, and there is no danger of any damage or injuries, but a number of people have reported feeling it in the town of Penicuik.

 The approximate location of the 3 December 2014 Midlothian 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... Two Earthquakes in Perthshire in two days.   On Friday 21 September 2012, a few seconds before 10.30 am British Summertime (a few seconds before 9.30 am GMT) the British Geological Survey recorded a Magnitude 1.4 Earthquake 2 km beneath the village of Comrie in west Perthshire, Scotland. Less than a day later, slightly before 8.40 am British Summertime (slightly before 7.40 am GMT) on Saturday 22 September, a second Earthquake, with a magnitude of...
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