The intense battle under way to control the nuclear plant at Fukushima Daiichi is unprecedented in scope – never before have multiple reactors been at risk of full meltdown – but it has also revived one of the longest-running debates in the industry: how safe is it to build an atomic reactor in an area that is at risk of an earthquake?

There are currently more than 400 reactors in operation around the world and about 90 of these are operating in areas of significant seismic activity, according to the latest figures from the World Nuclear Association. How worried should we be?

In the US, although some environmentalists are concerned about the potential threat to nuclear plants in the Midwest from the New Madrid faultline, the industry sees the greatest dangers as generally arising in the earthquake zones of the west coast.