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Educational guide, not an alert service: no live data. Always follow official instructions from JMA, your municipality, police, fire and staff. In an emergency, protect yourself first. Full disclaimer

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Japan alert decoder · 大津波警報

Major Tsunami Warning

Evacuate now from dangerous places · official rules as of 2026-10-17

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Evacuate now from dangerous places

大津波警報

Major Tsunami Warning

A tsunami higher than 3 m is expected. Heights are announced as 5 m, 10 m or over 10 m; right after a huge quake JMA may only say 巨大 (huge). Near the source, waves can arrive within minutes.

What to do now

  1. Evacuate immediately to high ground or a tsunami evacuation building (津波避難ビル), as high as you can.
  2. Go on foot unless you must drive; leave the coast and river mouths.
  3. Don't go back: tsunami waves repeat for hours and later waves can be bigger.

Don't

  • Don't go to the shore to look.
  • Don't wait to confirm the height.

How long: Stay evacuated until the warning is lifted (解除), often many hours.

Issued by: JMA (a special-warning class alert). Live status: JMA warnings map (English)JMA earthquake information (English)JMA tsunami information (English)

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Educational guide, not an alert service: no live data. Always follow official instructions from JMA, your municipality, police, fire and staff. In an emergency, protect yourself first.

Data as of 2026-10-17 from official JMA, Cabinet Office, Cabinet Secretariat (J-ALERT) and Ministry of the Environment pages, with official names from the JMA multilingual dictionary (2026-03-26). Not affiliated with JMA or any government agency.

Educational guide, not an alert service: no live data. Always follow official instructions from JMA, your municipality, police, fire and staff. In an emergency, protect yourself first. Data as of 2026-10-17 from official JMA, Cabinet Office, Cabinet Secretariat (J-ALERT) and Ministry of the Environment pages, with official names from the JMA multilingual dictionary (2026-03-26). Not affiliated with JMA or any government agency.