March earthquake and tsunami that hit Japan has increased the possibilities of earthquakes, which increases the danger on Fukushima nuclear plant. The research calls for the Japanese to maximize the security on the Fukushima Daiichi nuclear power plant in order to resist the possible earthquakes. The research was done according to a tremor that occurred about 160 km from the site of the Fukushima Daiichi nuclear power plant, and it is possible that another tremor can occur near Fukushima.
The research now published in EGU’s Solid Earth 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 northeast 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.
The number of earthquakes in Iwaki increased greatly after the March earthquake. The movements in the Earth’s crust induced by the event caused variations in the seismic pressure or stress of nearby faults. Around Iwaki, Japan’s seismic network recorded over 24,000 tremors from 11 March 2011 to 27 October 2011, up from under 1,300 detected quakes in the nine years before, the scientists report.
The 6,000 of these earthquakes selected for the study were recorded by 132 seismographic stations in Japan from June 2002 to October 2011. The researchers analysed these data to take pictures of the Earth’s interior, using a technique called seismic tomography.
The map of Japan’s islands indicating the area of study (black box). The purple star marks the epicentre of the 11 March earthquake and the red star the Iwaki epicentre. Fukushima Daiichi is highlighted by a red square. Black triangles indicate active volcanoes. Numbers on the side of the image represent latitude and longitude. Credit: Ping Tong, Dapeng Zhao and Dinghui Yang.