The disastrous magnitude 9.0 earthquake that shook Japan on March 11 of last year greased the wheels for another quake.
The quake allowed fluids to move upward in the Earth’s crust, which lubricated seismic faults and increased the chance that they will give way and rattle the region again.
Geophysicists have been studying the faults and released their findings in the European Geosciences Union’s journal Solid Earth.
“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 team-leader Dapeng Zhao, geophysics professor at Japan’s Tohoku University, in a press release.
Zhao’s team paid close attention to the magnitude 7 aftershock that struck Iwaki on April 11. The geophysicists were able to determine that fluids released as the Pacific tectonic plate slides underneath northern Japan had made their way past denser molten rock and were making it easier for faults to give way.
“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,” said Ping Tong, lead author of the paper, in a press release.
The technology used to peer beneath the Earth’s surface was similar to what oncologists and other doctors use to glimpse the interior of a person.
“The method is a powerful tool to map out structural anomalies, such as ascending fluids, in the Earth’s crust and upper mantle using seismic waves. It can be compared to a CT or CAT scan, which relies on X-rays to detect tumors or fractures inside the human body,” said Zhao.
Diagnosing tectonic trouble could be the geological equivalent of preventive medicine since it warns of future danger near the Fukushima nuclear power plant.
The damage to the Fukushima nuclear plant caused by last year’s tsunami that followed the quake resulted in one of the largest nuclear disasters in history. The authors of the Solid Earth study warn that the plant must be reinforced to withstand future hazards.
The Fukushima I Nuclear Power Plant after the 2011 Tōhoku earthquake and tsunami (Digital Globe, Wikimedia Commons)
Diagram of the March 11 earthquake (W. Rebel, Wikimedia Commons)