By DAMIEN GAYLE
Scientists have issued a dire warning that the damaged Fukushima nuclear plant is at risk of a massive new earthquake. Research using data from more than 6,000 recent tremors has found that last March’s disaster has reactivated a seismic fault practically beneath the power station.
Now scientists are telling Japanese authorities to urgently shore up the damaged reactor in expectation of more massive ‘quakes. Fukushima Daiichi was the scene of the worst nuclear disasters in history after it was damaged by the March 11, 2011, magnitude 9 earthquake and following tsunami.
But this tremor’s epicentre was about 100 miles from the site, off the coast of Japan, and a much closer one could occur in the future at Fukushima.
Dapeng Zhao, geophysics professor at Japan’s Tohoku University, said: ‘There are a few active faults in the nuclear power plant area, and our results show the existence of similar structural anomalies under both the Iwaki and the Fukushima Daiichi areas.
‘Given that a large earthquake occurred in Iwaki not long ago, we think it is possible for a similarly strong earthquake to happen in Fukushima.’
The April 11, 2011, magnitude 7 Iwaki earthquake was the strongest aftershock of the 11 March earthquake with an inland epicentre. It occurred 37 miles south-west of the Fukushima nuclear power plant, 124 miles from the March 11 epicentre.
The research, published in European Geosciences Union’s open-access Solid Earth journal, shows that the Iwaki earthquake was triggered by fluids moving upwards from the subducting Pacific plate to the crust. The Pacific plate is moving beneath north-east Japan, which increases the temperature and pressure of the minerals in it.
This leads to the removal of water from minerals, generating fluids that are less dense than the surrounding rock. These fluids move up to the upper crust and may alter seismic faults.
Ping Tong, lead author of the paper, said: ‘Ascending fluids can reduce the friction of part of an active fault and so trigger it to cause a large earthquake. ‘This, together with the stress variations caused by the 11 March event, is what set off the Iwaki tremor.’