Expert: Unreleased Strain May Remain Near March 16 Quake Epicenter
An expert on earthquake mechanisms says there may be unreleased strain in the area around the epicenter of the magnitude 7.4 quake that struck Japan on March 16.
Professor Toda Shinji of Tohoku University analyzed the amount of strain, which causes earthquakes, in an area around the epicenter off Fukushima Prefecture.
He says strain from the massive earthquake that hit northeastern Japan on March 11, 2011, had accumulated in the area. It could trigger further quakes within the Pacific sea-side plate, which slipped under the land-side plate. This is thought to have led to the magnitude 7-class tremors in April 2011 and in February last year in the coast off Fukushima Prefecture.
Toda compared the areas with faults that shifted in last week's quake with those of these past quakes.
He found areas which could move in the future between the faults from last week's quake and the April 2011 tremor.
Toda has expressed concern that a quake similar to the one last week could recur inside the plate. He says that when areas are hit by frequent strong temblors, buildings there could be heavily damaged. He calls on people to inspect structures and make other preparations in advance.
Toda also says last week's earthquake has caused strain to accumulate not only within the sea-side plate but also at the plate boundary, making it more likely for additional quakes to occur.
He says that earthquakes in shallow areas along the plate boundary could trigger tsunami.