Sunday 13 December 2015

Magnitude 3.8 Earthquake off the west coast of Norway.

The British Geological Survey recorded a Magnitude 3.8 Earthquake at a depth of 10 kmabout 30 km offshore of the town of Florø in Sogn og Fjordane County, southern Norway, slightly after 8,20 am local time (slightly 70.20 am GMT) on Friday 11 December 2015. There are no reports of any damage or injuries associated with this event, though it is likely to have been felt locally.
 The approximate location of the 11 December 2015 Norwegian coastal Earthquake. Google Maps.
Earthquakes are rare in Norway, and the waters between them, and those that do occur tend to be small, which makes the causes hard to determine. The entire of Europe is being pushed eastward by the expansion of the Atlantic Ocean and northward by the impact of Africa from the south, though these are remote from the Kattegat. There are lesser areas of expansion beneath the North Sea and Rhine Valley, both of which will presumably have some effect on southern Scandinavia. 
Finally their is glacial rebound; until about 10 000 years ago much of northern Europe was covered by a thick layer of ice. This pushed the rocks of the lithosphere down into the underlying mantle, and now that the ice is gone these rocks are springing back up, albeit very slowly, a process which is not smooth as rocks tend to stick to one-another, and which therefore causes the occasional small Earth tremor.
 (Top) Simplified diagram showing principle of glacial rebound. (Bottom) The extent of glaciation in Europe at the last glacial maximum. Wikipedia.
Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organization Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.
See also... 3.6 Earthquake in Hjelmeland, southern Norway.                                 The British Geological Survey recorded a Magnitude 3.6 Earthquake at a depth of 10 kmin the east of the Hjelmeland Municipality in Rogaland County, southern Norway, slightly after 0.45 am local... 4.7 Earthquake in Dalarna County, Sweden.                                           The United States Geological Survey recorded a Magnitude 4.7 Earthquake at a depth of 14.3 km in Dalarna County, Middle Sweden, slightly before...
Lake Vättern is the second largest lake in Sweden. It lies in the south of the country, and is 135 km long and 31 km in width at its widest...
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