Sanriku offshore earthquake
Historical term referring to major earthquakes off the Sanriku coast, especially those of June 15, 1896, March 3, 1933, and March 11, 2011.
The Sanriku offshore earthquake has caused major tsunamis many times in the past.
Compound of 三陸 (Sanriku, a region in northeastern Japan), 沖 (offshore), and 地震 (earthquake).