Monday, 20 February 2017

Two Earthquakes in North Lincolnshire.

The British Geological Survey recorded a Magnitude 1.5 Earthquake at a depth of 16 km, about 10 km to the southeast of the town of Grimsby in north Lincolnshire, slightly after 5.30 am GMT on Friday 17 February 2017. This was followed by a second quake with a Magnitude of 1.3 at roughly the same location about 6.5 minutes later. These quakes were not large enough to have caused any damage or injuries, but may have been felt locally.
 
The approximate location of the 17 February 2017 Lincolnshire Earthquakes. Google Maps.
 
Earthquakes become more common as you travel north and west in Great Britain, with the west coast of Scotland being the most quake-prone part of the island and the northwest of Wales being more prone  to quakes than the rest of Wales or most of England. However, while quakes in southern England are less frequent, they are often larger than events in the north, as tectonic pressures tend to build up for longer periods of time between events, so that when they occur more pressure is released.

Earthquakes become more common as you travel north and west in Great Britain, with the west coast of Scotland being the most quake-prone part of the island and the northwest of Wales being more prone  to quakes than the rest of Wales or most of England. However, while quakes in southern England are less frequent, they are often larger than events in the north, as tectonic pressures tend to build up for longer periods of time between events, so that when they occur more pressure is released.
 
Britain 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. It is also affected by lesser areas of tectonic spreading beneath the North Sea, Rhine Valley and Bay of Biscay. Finally the country is subject to glacial rebound; until about 10 000 years ago much of the north of the country was covered by a thick layer of glacial ice (this is believed to have been thickest on the west coast of Scotland), pushing the rocks of the British lithosphere down into the underlying mantle. This ice is now gone, and the rocks are springing (slowly) back into their original position, causing the occasional Earthquake in the process.
 
(Top) Simplified diagram showing principle of glacial rebound. Wikipedia. (Bottom) Map showing the rate of glacial rebound in various parts of the UK. Note that some parts of England and Wales show negative values, these areas are being pushed down slightly by uplift in Scotland, as the entire landmass is quite rigid and acts a bit like a see-saw. Climate North East.
 
Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. If you felt the first quake, or were in the area but did not (which is also useful information) then you can report it to the British Geological Survey here, and if you felt the second quake (or did not) then you can report it here.
 
See also...
 
http://sciencythoughts.blogspot.co.uk/2016/05/magnitude-13-earthquake-in-lincolnshire.html
http://sciencythoughts.blogspot.co.uk/2017/01/magnitude-38-earthquake-beneath.html
 
http://sciencythoughts.blogspot.co.uk/2016/02/nottinghamshire-sinkhole-traps-car.html
http://sciencythoughts.blogspot.co.uk/2016/04/magnitude-14-earthquake-near-barton.html
http://sciencythoughts.blogspot.co.uk/2015/09/magnitude-28-earthquake-in-rutland.html
http://sciencythoughts.blogspot.co.uk/2015/11/series-of-earthquakes-in-north.html

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