Earthquake! Somebody call a geologist!

A small earthquake hit just off the coast of North Wales today, registering 3.8 on the Richter scale. Not massive news, but newsworthy nonetheless.

Now usually when there is an earthquake in Britain, is makes the news, not because it is a disaster, but because it is a curiosity. Generally speaking, a news person will interview somebody from the British Geological Survey or some such organisation and ask them a fairly standard set of questions. Usually they'll ask how big it was, possibly in relation to other earthquakes and the usual reply will be 'not very'. The thing that always puzzles me however, is that nobody every explains why they happen. They explain that earthquakes occur along tectonic plate boundaries, because the plates are moving and can rub along, against, above or below each other. But Britain isn't near any plate boundaries. To be fair to the news, this is usually explained, but my issue is that they don't go any further. Why do they never ask why this exact earthquake has happened at the exact point that it did?

I have come up with a few theories based on my limited knowledge of plate tectonics. My first theory is that there are earthquake hotspots, much like the volcano hotspot theory, but for earthquakes. Essentially there is a weaker or thinner spot in the plate which means that waves of energy moving through the plates have a greater effect as they move through this spot. The other possibility is that there are certain points where there are cracks in the plates and as the plate moves the cracks are opened and then pushed back together again. My final dubious theory is that certain points under the plates, in the magma's convection currents, are hotter than others, causing the hot magma to rise more quickly than that surrounding it and almost bubble up into the underside of the tectonic plate, causing an earthquake.

In summary, I don't completely know what I'm talking about, but I'm not sure geologists have much of a better understanding. I'll be happy to be proved right or wrong, I just want an answer. Comments in the box below please geologists. Thanks.