The D-1 fault runs beneath the No. 2 reactor, and the government doesn't allow nuclear-power plant operators to build reactors directly above active faults.

WSJ: Panel: Active Fault Runs Beneath Japan Reactor

There are a number of active faults that line the Midlands Microcraton, and many of the tremors experienced on the western side of the English Midlands, up to the Pennines, are a result of rocks jostling in this area.

BBC: Q&A: UK's small-scale earthquakes