Martyh you might want to read these links. Tells you that scientist dont much know about intraplate earthquakes to understand how they happen where the risks are. They learning all the time about these type earthquakes these are the type uk get. In netherlands was pretty immune got 5.8 which damaged structures.
http://en.wikipedia.org/wiki/1992_Roermond_earthquake
Its was thought they we very infrequent but that thinking subsiding. Scientist accept three types caused by stress, heat or weakness fig 2. following link
http://www.experimentation-online.co...le.php?id=1316
Its these earthquakes not near the main plates can be just violent deadly. I dont want you have nightmares
but we not immune.
This will give you idea where most at risk next 50 years darker the risks damage to property. Although they estimate only 10% chance of this.
http://www.earthquakes.bgs.ac.uk/hazard/UKhazard.html
Another is the 2 most recent earthquakes study been conducted
http://www.earthquakes.bgs.ac.uk/res...rketrasen.html
some other stuff might want read
http://www.bgs.ac.uk/research/earthq...s.html?src=sfb
http://nora.nerc.ac.uk/5356/
Which means historic earthquakes may been stronger as it difficult to assess.
Now biggest recorded earthquake was offshore dogger bank near coast yorkshire.
http://en.wikipedia.org/wiki/1931_Do...ank_earthquake
DATE 07/06/1931
ORIGIN TIME 00:25:00 UTC
LOCATION 54.080 1.500
DEPTH 23.0 km
MAGNITUDE6.1 ML
LOCALITY NORTH SEA
http://www.earthquakes.bgs.ac.uk/ear...UKseismic.html