M9.0 Earthquake Strikes Off Tōhoku Coast

At 14:46 JST on March 11, 2011, a magnitude 9.0–9.1 megathrust earthquake—the most powerful ever recorded in Japan—struck 70 km east of the Oshika Peninsula at a depth of ~30 km. The earthquake lasted approximately 6 minutes and triggered a massive tsunami warning across the Pacific. The Fukushima Daiichi plant experienced ground acceleration well beyond its design basis. All six reactor units scrammed (emergency shutdown) automatically.