Monday, 17 September 2012

Earthquake beneath the English Channel.

On Saturday 15 January 2012 at 4.25 pm local time (2.25 pm GMT), the British Geological Survey recorded an Earthquake beneath the English Channel, roughly 50 km northeast of Dieppe. The BGS recorded this as a Magnitude 2.4 quake with a depth of zero, and suggest that this may have been a submarine explosion, however the Bureau Central Sismologique Français recorded the same quake as having a Magnitude of 3.0 at a depth of 2 km, which would seem to rule this out. Either way this quake is far to small and to far offshore to present any risk.

The location of the 15 September 2012 quake. Google Maps.

The precise causes of quakes beneath the English Channel can be hard to determine (assuming this is not the result of a submarine explosion). The area is not close to the edge of a tectonic plate that would provide a ready explanation for such quakes. The area, along with the rest of Europe, is being pushed eastwards by the expansion of the Atlantic Ocean and Northward by the impact of Africa into Europe from the south. There are also lesser areas of expansion beneath the North Sea, Rhine Valley and Bay of Biscay, all of which exert tectonic stresses in the area. Finally there is glacial rebound; until about 10 million years ago much of the north of Europe was covered by a thick layer of ice, which pushed the rocks of the lithosphere down into the underlying mantle. Now this ice is gone, and the rocks are slowly springing back, causing the occasional Earthquake in the process.


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