Friday, 20 July 2012

Earthquake in the Channel Islands.

On Tuesday 17 July 2012, at approximately 1.54 pm British Summertime (12.54 pm GMT), an Earthquake occurred in the Channel Islands roughly 10 km north of the island of Jersey (15km west of the Cherbourg Peninsula) at a depth of 5 km, according to the British Geological Survey, who measured the quake as having a magnitude of 1.4 on the Richter Scale. A tremor this small is unlikely to have caused any damage or injuries, and happening 10 km offshore it is likely that nobody noticed the event at all.

Map showing the location of the 17 July 2012 Earthquake. BGS.

The Channel Islands suffer the occasional Earthquake, though these are seldom large, the last such event being in December 2009, to the south of Jersey. The last major Earthquakes in the area were in 1926 & 1927 when two Earthquakes on the Normandy coast, both estimated at 5.5 on the Richter Scale, were felt in the Islands. 

Due to the small size and rarity of quakes in the Channel Islands it is seldom possible to be precise about their exact cause. Northwestern Europe is subject to tectonic stresses from a number of sources, though none of these is overwhelming. The entire of Europe is being pushed to the east by the expansion of the Atlantic Ocean, and to the north by the movement of Africa from the south. There are also lesser areas of expansion beneath the North Sea, the Rhine Valley and the Bay of Biscay, all of which exert stresses in the Channel Islands region. Finally there is glacial rebound; much of northern and upland Europe was covered by thick ice until about 10 000 years ago, which pushed the rocks of the lithosphere down into the underlying mantle. Now this ice has gone the rocks are slowly rising back up, causing the occasional Earthquake in the process, though it is unclear the extent to which this affects the Channel Islands.


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