Japanese scientists say they have found evidence of displacement of the tectonic plates caused by the March 11th earthquake last year.
A team from the Japan Agency for Marine-Earth Science and Technology conducted an acoustic wave study last year along the Japan Trench about 250 kilometers off the coast of Miyagi Prefecture. The study assessed the seabed structure to a depth of several kilometers.
The findings showed at least 2 displacements near the trench axis where the Pacific plate begins to sink below the plate underneath northeastern Japan.
The scientists say fault ruptures from the quake's epicenter located in the deep part of the plate boundary reached the seabed surface.
They say structural upheavals along the fault indicate big earthquakes have occurred repeatedly in the area.
A senior agency official says a detailed seabed survey is needed to uncover the mechanism of massive quakes and how often they occur.