Areas in the ocean floor off the coast of Miyagi Prefecture, site of the epicenter of the Great East Japan Earthquake, have characteristics that make them particularly prone to major earthquakes, a Tohoku University research team found.
Areas in the ocean floor off the coast of Miyagi Prefecture, site of the epicenter of the Great East Japan Earthquake, have characteristics that make them particularly prone to major earthquakes, a Tohoku University research team found.
Those areas of solid bedrock extend close to the Japan Trench, according to the team, led by Zhao Dapeng, professor of seismology at the university.
“This new study could also help identify which sea bottom areas will likely trigger earthquakes in other waters,” Zhao said.
The border areas between continental and oceanic plates in the Pacific Ocean off the Tohoku region have different structures. Using data from previous earthquakes, the researchers studied the speed of seismic waves, which tend to accelerate in solid bedrock but slow down in softer bedrock.
They found that the epicenters of earthquakes of magnitude 6 or more were concentrated either in solid bedrock or in the borders between solid and soft bedrock.
In solid bedrock, the continental and oceanic plates are firmly bonded, leading to an accumulation of stress that can cause huge earthquakes when released.
By contrast, in softer bedrock, the plates are more loosely connected, and stress does not accumulate to significant levels, the team said.