A research team says that heat-swollen water in ocean bedrock off northern Japan may have intensified the fault displacements that led to the devastating 2011 earthquake, increasing the size of the tsunamis.
Earth scientists from ten nations including Japan, the United States and European countries say water in deep sea bedrock expanded due to frictional heat caused by the 2011 earthquake. This made the tectonic plates in the area more slippery, helping to trigger their large-scale movement. This phenomenon may have increased the size of the tsunami that followed the tremor, Japan's NHK broadcaster reported on Tuesday quoting the scientists.
The team last year conducted a study of the tectonic stress mechanism that caused the quake and tsunami. They drilled a borehole into the ocean floor of the Japan Trench, a collision zone of tectonic plates whose movement was responsible for the massive quake and tsunami in Tohoku.
The researchers found that bedrock 820 meters below the seabed at a tectonic plate boundary had a content of 70 percent clay. This clay bedrock exhibited moisture permeability 100 to 1,000 times lower than other bedrock. Temperature of the bedrock was also found to be higher by up to 0.3 degrees Celsius.
They estimate that the tectonic movement caused friction heat reaching hundreds of degrees Celsius. Expansion of the water made the bedrock slide further, increasing the scale of the tsunami waves.
The March 11, 2011 earthquake and the ensuing tsunami left more than 20,000 people dead or missing besides devastating Japan's northeast. It also knocked out the Fukushima Daiichi nuclear power plant leading to massive radiation leak that forced the evacuation of over 160,000 residents in a 30-kilometer radius of the stricken plant, which is under the process of decommissioning.
Plant operator Tokyo Electric Power Company (TEPCO) is now struggling to prevent the leak of radioactive waste water from the plant after about 300 tons had already been leaked out, with some quantity reaching the nearby Pacific Ocean.
by RTT Staff Writer
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