The magnitude 8.8 earthquake that jolted northeast Japan was caused by a tectonic upheaval that created offshore faults stretching for hundreds of kilometers from Iwate Prefecture to Ibaraki, seismologists said Saturday.
Satoko Oki of the University of Tokyo's Earthquake Research Institute said the massive quake, estimated to be nearly 1,000 times more powerful than the 1995 Great Hanshin Earthquake that killed more than 6,000 people, was caused by a rupture near the boundary between the Pacific and North American tectonic plates.
The quake was created when the Pacific plate slipped under Japan at the Japan Trench, causing tsunami as high as 10 meters to slam the east coast, she said.