Tuesday 8 May 2012

Earthquake in Burnley, Lancashire.

On Monday 7 May 2012, at 8.20 pm GMT (9.20 pm British Summertime), the British Geological Survey recorded an Earthquake slightly to the northeast of Burnley in Lancashire, measuring 1.6 on the Richter Scale, at a depth of 17 km. Such a small quake at this depth is highly unlikely to have been felt, much less to have caused any damage or injuries at the surface.

The location of the 7 May quake. BGS.

The UK is not considered a particularly quake-prone country as it is not close to any tectonic margins and seldom suffers large quakes, but small quakes like this are not uncommon, and as a rule-of-thumb are more common the further north and west you go in the country. A number of sources of tectonic stress contribute to this. Firstly the Atlantic is spreading along its central ridge, pushing Eurasia eastwards (and North America to the west). Then Africa is pushing into Europe from the south, which causes uplift in the Alps and tectonic stress across Europe; this causes more tremors in the east Mediterranean region, but the rest of the continent is not immune. Then there are smaller spreading centers beneath the North Sea, Bay of Biscay and Rhine Valley, all of which excerpt some pressure on the UK. Finally there is glacial rebound; the north of Britain was covered by ice several hundred meters thick till about 10 000 years ago, which pushed the rocks of the lithosphere down into the underlying mantle slightly. Now this ice has gone the rocks are rebounding, at geological speeds, a process that will probably continue for thousands of years yet to come.

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