The 2011 Tōhoku Earthquake and Tsunami
A magnitude 9.1 megathrust earthquake off northeastern Honshu generated a tsunami that reached the coast within about 30 minutes. The water overtopped defenses, destroyed communities, and caused more than 18,000 deaths and missing persons. Flooding disabled power and cooling at Fukushima Daiichi, leading to a major nuclear accident.
- When
- 11 March 2011Exact day
- Where
- Pacific coast of Tōhoku, northeastern HonshuJapan · General area
- Evidence
- VerifiedSources reviewed below
- Sensitivity
- Highly sensitive subjectPresented with care
The place
Before
What existed before
Japan had extensive earthquake-resistant construction, coastal defenses, public drills, and one of the world’s most advanced warning systems. Historical deposits showed that very large tsunamis had reached the region, but assumptions used for some defenses and emergency plans underestimated the 2011 event.
Cause
Trigger and conditions
A huge area of the plate boundary east of Honshu ruptured, displacing the seafloor. The resulting tsunami crossed the Pacific and grew dramatically in shallow coastal water. Along parts of Tōhoku it reached heights approaching 40 meters.
Sequence
Timeline
Magnitude 9.1 earthquake
A megathrust rupture begins offshore of northeastern Honshu.
Tsunami reaches the coast
Successive waves inundate a long stretch of the Pacific coastline.
Fukushima emergency escalates
Loss of power and cooling leads to core damage and releases at Fukushima Daiichi.
Reconstruction and policy change
Communities rebuild while warning, engineering, and nuclear systems are reassessed.
After
Aftermath
Search, rescue, shelter, and recovery unfolded amid destroyed transport and utilities, winter conditions, displacement, and the Fukushima emergency. Communities faced the loss of residents, homes, records, workplaces, and familiar coastlines.
Long-term consequences
Japan revised tsunami assumptions, evacuation planning, coastal engineering, and nuclear regulation. Globally, observations from deep-ocean sensors improved real-time forecasting. Recovery and memorialization continue, with difficult debates over relocation, seawalls, energy, and community continuity.
Significance
The essential question
Why this still matters
Tōhoku shows both the life-saving value and the limits of preparedness. It connects geologic history, warning systems, land-use choices, critical infrastructure, community memory, and cascading technological risk across an entire coastline.
What remains today
Memorial parks, preserved ruins, raised settlements, new defenses, evacuation markers, museums, and annual observances reshape the coast. The Fukushima Daiichi site remains in a long decommissioning process.
Media
Historical media
Pacific propagation of the 2011 tsunami
A scientific visualization follows tsunami energy across the Pacific using observations and modeling.
NOAA · NOAA educational visualization; see source for dataset and production credits.View at sourceEvidence
Sources
Sources support specific claims; inclusion does not imply that every source is equally authoritative on every question.
- 01On This Day: 2011 Tohoku Earthquake and Tsunami
NOAA National Centers for Environmental Information
Updated NOAA overview of magnitude, losses, inundation, infrastructure effects, and preparedness lessons.Open source - 02Tsunami Historical Series: Japan — 2011
NOAA Science On a Sphere
Pacific-scale chronology, wave observations, warning activity, and visualization.Open source