How strong was the earthquake that triggered the Japan tsunami of 2011?

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earthquake damage, Honshu, Japan, 2011 — Japan earthquake and tsunami of 2011 Aerial view of damage to a portion of the northeastern coast of Honshu, Japan, following the offshore earthquake and resultant tsunami there on March 11, 2011.

The earthquake that triggered the 2011 tsunami was a magnitude-9.0 event. While initial estimates placed the magnitude at 8.9, this figure was later revised upward.12

Occurring on March 11, 2011, the earthquake was the strongest to strike the region since record-keeping began in the late 19th century and is considered one of the most powerful earthquakes ever recorded. It was caused by the rupture of a subduction zone along the Japan Trench, where the Pacific Plate lurched beneath the Eurasian Plate (or the Okhotsk microplate).1