Fukushima rocked by another quake; nuclear plant briefly disrupted

Japanese living in and near the seismically active Fukushima prefecture were jolted early Tuesday morning by another major earthquake.

Media reports said the quake, which was felt as far south as Tokyo, initially was reported as having a magnitude of 7.3, but was later downgraded to 6.9. In comparison, the megathrust earthquake and tsunami of 2011, which struck off the Pacific coast of northern Japan, was a magnitude 9.1. Known in Japan as the Great East Japan earthquake or the 2011 Tōhoku earthquake, that event – recorded as the most powerful ever to hit Japan and the fourth most powerful earthquake in the world – is seared into collective memory for the damage and death it caused.

Hundreds of thousands of buildings collapsed and tsunami waves reaching as high as 40 metres travelled up to 10 kilometres inland. The tsunami engulfed the Fukushima Daiichi nuclear power plant, spilling radiation into the air and sea, causing the evacuation of at least 100,000 residents. Over 18,000 people were killed or reported missing.

The Japanese earthquake is also recalled as a watershed event for uranium, whose price essentially fell off the cliff and led to a major rethink of nuclear power.

While nothing of the scale of the 2011 earthquake is evident from recent news – there were no reported deaths or serious injuries and the tsunami threat has now largely passed – there have been reports that one of the cooling systems at one of the reactors briefly failed.

According to Reuters, Tepco said the cooling system for spent nuclear fuel on the third reactor of the Fukushima plant was halted for a brief period, then restarted. Temperatures rose slightly but were within safety limits, Cabinet Chief Secretary Yoshihide Suga said at a televised news conference.

No other damages or abnormalities have been reported at other nuclear facilities.

After the March, 2011 earthquake, all of Japan's nuclear reactors were shut down and tested for safety. Even though most of the plants are shuttered, their cooling systems must keep operating to cool the spent fuel.

There are currently only two reactors operating in Japan, both in the southwestern part of the country; operators of those plants say they have not been damaged.