Scientists report the magnitude 9 earthquake which struck northeast Japan last March caused stress variations in an underlying active fault and could lead to another quake much closer to the meltdown site at Fukushima’s Daiichi nuclear plant.
New tremors, due to a reactivated seismic fault, are occurring much closer to the Daiichi nuclear facility than the epicenter of last year’s devastating earthquake which triggered a tsunami, nuclear meltdowns and an environmental calamity in northeast Japan.
“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,” said Dapeng Zhao, geophysics professor at Tohoku University in Japan, according to a statement in European Geosciences Union.
EGU’s Solid Earth has published research (pdf) showing the Iwaki earthquake of April 11, 2011, with a 7 magnitude has been the strongest aftershock since the March 11 disaster began unfolding. It occurred about 60 km (37 miles) southwest of Fukushima, and had an inland epicenter.
This aftershock was triggered when fluids moved up to the crust from the subducting Pacific plate, according to the scientists. The March earthquake set into motion a great increase in the number of earthquakes in Iwaki, and movements in the earth’s crust have caused seismic pressure or stress variations of nearby faults.
According to the newly published research, the seismic network around Iwaki recorded more than 24,000 tremors from March 11 to October 27 last year. This number was up from less than 1,300 detected quakes during the nine years before.
The scientists warn because of the increased probability of an earthquake near Fukushima,
more attention should be paid to the site’s ability to withstand strong earthquakes, and reduce the risk of another nuclear disaster.