The power of the magnitude-9.0 Great East Japan Earthquake may have been the result of a huge accumulation of energy caused by a seamount stuck along the plate boundary, a team of scientists said.
The power of the magnitude-9.0 Great East Japan Earthquake may have been the result of a huge accumulation of energy caused by a seamount stuck along the plate boundary, a team of scientists said.
"It used to be thought that giant earthquakes, so big as the latest one, do not take place along the Japan Trench where the plate coupling is weak," said Hiroyuki Kumagai, a senior researcher at the National Research Institute for Earth Science and Disaster Prevention (NIED), who led the team. "Our hypothesis may help to explain the mechanism by which the mega-quake occurred."
Plate boundaries, like the Japan Trench, where an oceanic plate subducts beneath a continental plate, have specific locations where the plates are usually strongly coupled. When the accumulated energy exceeds a sustainable limit, the areas "snap," resulting in a great earthquake.
Kumagai and his co-workers analyzed the source of the March 11 earthquake using NIED's seismic observation data and found that an area along the plate boundary, about 70 kilometers in radius, was firmly stuck together before the earthquake.
This area is believed to represent an old seamount on the oceanic plate that had subducted beneath the continental plate. The scientists said the seamount likely became stuck, causing a strong plate coupling and promoting the accumulation of a large amount of energy over an extended period.
The research results will be presented at a meeting of the Seismological Society of Japan that opens in Shizuoka on Oct. 12.