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Japan’s ‘Great Tohoku’ Quakes Have Recurred, Data Show

The “Great Tohoku Earthquake” that shook Japan, unleashed a tsunami and killed 20,000 people last year wasn’t as unusual as geologists first supposed, according to new geological data collected near the fault lines.

Earthquakes like the March 11, 2011, temblor have probably occurred at least three other times in history, according to German, Swiss and Japanese scientists who drilled into sediment 7,000 meters (22,967 feet) beneath the sea. The discovery will help planners measure the risk of such events recurring, said Michael Strasser, a Swiss scientist who led a research expedition to the quake zone this month.