Chief nuclear inspector Mike Weightman has this week played down the relevance of the Japanese earthquake and resulting tsunami for the UK’s nuclear stock. But can the UK afford to be so complacent?
A magnitude 9 earthquake and an associated 14m high tsunami are far beyond the most extreme events the UK could expect to experience, he said (News this week).
But this month’s 5.2 magnitude earthquake in Lorca, Spain, showed that an event does not have to be as extreme as that to cause serious damage.
The UK has significantly less seismic risk than Mediterranean countries − but that risk is not zero.
Earthquake engineers told NCE last week that towns across Europe, like Lorca, have many historic buildings that have never been retrofitted to modern earthquake design standards due to heritage concerns.
The UK has its fair share of antiquated structures.
Of course, the UK has significantly less seismic risk than Mediterranean countries − but that risk is not zero. Small earthquakes are frequent in the British Isles. This month alone, quakes were observed in Scotland and the Isles of Scilly.
Every 20 years
Larger seismic events are not alien to Britain either. The British Geological Survey (BGS) says the UK is likely to experience one magnitude 5 earthquake every 20 years.
Events believed to be of magnitude 5 and above have occurred repeatedly since the 1100s, with especially serious events in Lincolnshire (1165), Wells (1248), and Colchester (1884).
And research by Bath Spa University has shown that serious flooding in the Severn Estuary in 1607 could have been caused by a tsunami.
Research by Bath Spa University has shown that serious flooding in the Severn Estuary in 1607 could have been caused by a tsunami.
The BGS notes that the rate at which earthquakes occur over the long term is generally believed, and confirmed by all available data, to be constant, and says that urbanisation and increasing populations increase the potential for damage from earthquakes.
The soft clays beneath London are especially susceptible to being shaken, it says.
Of course, the recession and the presence of threats such as flooding and coastal erosion that strike perennially mean the idea of making UK infrastructure resilient to serious earthquakes – at some inevitable cost – is risible.
But a look back at the country’s seismic records shows that a serious event in the UK is not beyond the realm of possibility.
With New Zealand, Japan and Spain reminding us what the human consequences of that could be, perhaps the earthquake engineering debate is one worth having again.