Tuesday 18 September 2012

Small Earthquake in the Western Highlands.

On Monday 17 September slightly after 9.25 am British Summertime (slightly after 8.25 am GMT) the British Geological Survey recorded a Magnitude 1.2 Earthquake at a depth of 2 km, slightly to the north of Upper Loch Torridon, in the Western Highlands. An Earthquake this small is unlikely to have caused any damage or casualties, and may not even have been noticed.

Map showing the location of the 17 September 2012 Earthquake. Google Maps.

As a rough rule of thumb Earthquakes become more common in Great Britain as you travel north and west, making the west coast of Scotland one of the more Earthquake prone areas of the country. The exact cause of such quakes is not always easy to determine, as the UK is not close to any active tectonic margin, but rather subject to seismic stress from a variety of different sources. Scotland, along with the rest of Eurasia, 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, though these are both fairly remote occurrences. Closer to home their are lesser spreading centers beneath the North Sea, the Rhine Valley and the Bay of Biscay, all of which excerpt some tectonic stress onto rocks beneath the UK. Finally there is Glacial Rebound; until about 10 000 years ago much of the north of Europe was buried beneath a layer of ice, hundreds of meters thick, which pushed the rocks of the lithosphere down into the underlying mantle. This ice is now gone, and the rocks of the lithosphere are slowly springing back into place, causing the occasional Earthquake in the process.

Witness accounts of Earthquakes help geologists to understand the processes and structures that cause them. If you felt this quake you can report it to the British Geological Survey here. If you were in the area but did not feel the quake you can still report this, as this is also useful information.

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