Non-tectonic earthquakes

[jake-the-peg]

China doll's question on the UK earthquake got me thinking.

We normally associate eathquakes with slippages along tectonic plates but last I heart Birmingham was not on one of these!

From a quick scan around the net, non-tectonic earthquakes seem to be classified as volcanic or artificial. - Neither of which seem to make sense

Are the infrequent earthquakes we get actually tectonic all that way away? or is there some ancient volcanic rumbling deep below the west midlands?

[China Doll]

Hi Jake,

Copied and pasted some stuff below that might help answer your question a bit but couldn't find too much myself on the topic.

Earthquakes hit Britain on a fairly regular basis. In fact, there can be as many as three in a week. Luckily, the geology beneath us is stable, and these tremors usually go unnoticed.

Although there are no living volcanoes on the British mainland, the UK has an interesting volcanic history. For instance, Edinburgh, the Scottish capital is built on an extinct volcano called Arthur's seat, the mountains of north Wales are the remains of a huge volcanic plateau and there are volcanic rocks distributed throughout the British Isles. Even in the Chalk of Southern England, many of the thin marl seams (eg. Newhaven Member) are now considered to be volcanic ash deposits. Volcanoes have therefore played a significant part in the geological history of the UK. None of the volcanoes will become active again in the foreseeable geological future.

[kempie]

http://www.earthquakes.bgs.ac.uk/earthquakes/e ducation/faqs/faq6.html

[brachiopod]

There is actually a bloody great subduction zone underneath the British Isles, albeit an ancient one.

Back in the early Palaeozoic (Cambrian / Ordovician), what is now Scotland lay at the edge of a large continent also consisting of much of North America and Greenland.

At the edge of another, much smaller continent (along with bits of Scandinavia) lay what is now England.

Both of these continents actually lay in the southern hemisphere, and were separated by a whole ocean, called the Iapetus Ocean.

This eventually closed up as the two continents moved toward eachother, and the oceanic crust was subducted beneath the continental crust.

When the two continents finally collided sometime in the Silurian (about 420 million years ago or so) it formed the Caledonian mountains, and Scotland and England finally became united.

[jake-the-peg]

Well I think "was" rather than "is" a subduction zone under the UK - I don't think it's doing too much subducting these days! :c)

Still somewhat amazing that stresses created in the mid-atlantic ridge can build up a thousand miles away and find a weak spot below Dudley!

You'd have thought a weak enough spot would be found closer.

Thanks all - Geology not my strongest science