offshore earthquake
Used as a suffix attached to a place name to indicate an earthquake whose epicenter is offshore near that location, e.g. 三陸沖地震 (Sanriku-oki earthquake).
The Sanriku-oki earthquake caused a massive tsunami in 2011.
2011 Tōhoku earthquake; Great East Japan Earthquake
Compound of 沖 (oki, 'offshore') and 地震 (jishin, 'earthquake').