Tsunami Procedure in Japan
Tsunami procedure in Japan starts with one rule: a felt quake near the coast means move to high ground now. Warnings, towers, and maps all support that first step.1
Procedures, fees, and requirements can change. Confirm current details at the Japan Meteorological Agency tsunami pages and your municipal disaster-prevention site.
Overview
When a large offshore quake strikes, JMA models the wave and issues a warning or advisory for each affected coastal region within about 3 minutes (as of current JMA practice; confirm current procedures with JMA).1 You do not wait for that message. Shaking at the shore is itself the evacuation order, and the warning catches up to confirm what you already did.
The First Minutes After a Coastal Quake
The diagram below is the whole procedure in one picture. Everything after it is detail.
Move First, Confirm Later
Leave for high ground the moment strong or long shaking stops, or the moment any shaking reaches you near the shore. JMA publishes estimated arrival times and heights once its warning goes out, which lets you judge how long to stay put.2 The 2011 Great East Japan Earthquake tsunami killed or left missing about 18,000 people, and its central lesson was that residents who left immediately survived overwhelmingly.3
Do Not Wait for Belongings or Official Word
Returning for bags, waiting to see the sea, or driving along the coast to check on family are the documented delay patterns. Post-2011 programs pushed drills, evacuation-route inspections, and diverse alert channels precisely because minutes decide outcomes.4 Things are replaceable; the head start is not.
A receding sea exposes the seabed before the first crest arrives. Anyone on the beach or seawall at that moment is already out of time. Move inland or upward instead.2
JMA Tsunami Warnings
JMA issues three tiers per coastal region across 66 defined coastal regions of Japan.5 Each tier names the expected wave and the action it demands.
| Tier | Meaning | Resident action |
|---|---|---|
| Tsunami advisory (津波注意報, tsunami chūihō) | A lower wave is expected | Leave the water and the shore, stay clear until cleared |
| Tsunami warning (津波警報, tsunami keihō) | A damaging wave is expected | Evacuate the shore and low ground to high ground |
| Major tsunami warning (大津波警報, ōtsunami keihō) | A wave of 3 meters or more is expected (as of current JMA criteria; confirm current criteria with JMA) | Evacuate to the highest available ground at once |
The table tiers follow JMA's three-category system, with the 3-meter major-warning line stated in JMA materials.1 Major tsunami warnings carry Emergency Warning status, the highest JMA classification.63
How Warnings Reach You
Warnings travel from JMA through the J-Alert satellite system to local governments within seconds, then out to residents through municipal disaster radio, outdoor speakers, emergency alert emails to phones, TV, and radio.47 J-Alert carries earthquake early warnings and major tsunami warnings among its instant categories.7 Keep your phone's emergency alerts enabled and learn your municipality's speaker pattern during drills.
Vertical Evacuation and Evacuation Towers
When debris, distance, or crowds block the road uphill, go up instead of out. Enter a sturdy reinforced-concrete building and climb above the expected wave, ideally the third floor or higher.
The Vertical-Evacuation Rule
Vertical evacuation is the fallback, not the plan: high ground first, upper floors when high ground is unreachable. Post-2011 inspections checked the seismic strength of evacuation routes and buildings and pushed retrofits, which is why designated buildings now appear on municipal maps.4
Evacuation Towers
Coastal cities built dedicated 避難タワー (hinan tawā, "evacuation towers"): steel or concrete structures whose only job is to hold people above the water.4 If you live near the coast, find your closest tower and walk the route before any warning. Towers are municipal infrastructure, so their locations live on your city's map, not on any national list.
Know Your Zone Before the Day
Check the MLIT disaster prevention portal for the national earthquake and tsunami picture, then open your municipality's own hazard map for its tsunami zones, tower list, and shelter assignments.8 Post-2011 guidance explicitly calls on residents to re-examine municipal hazard maps, and your zone on that map sets your evacuation timing.4
Good to Know
The sea may arrive before any warning you hear
Warnings take about 3 minutes to issue (as of current JMA practice; confirm current procedures with JMA), and near-shore waves can land inside that window.1 Treat shaking as the warning and the broadcast as confirmation.
A weak shake can still precede a wave
Distant and slow-slip earthquakes can send a wave with modest local shaking. The advisory tier exists for exactly these events, so an advisory without drama still means leaving the water.6
Waves come in series, so one retreat is not the end
JMA publishes arrival times and heights as evolving information, and later waves can exceed the first.2 Stay high until the municipality or JMA clears your region.