SAFETY GUIDE · BASED ON OFFICIAL SOURCES

What to Do in a Tsunami: From the Moment the Shaking Stops to the All-Clear

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By the time you can see a tsunami, it's too late to start running. But if you know what to do ahead of time, you can almost always survive. The Japan Meteorological Agency's core advice fits in one sentence: if you feel strong shaking, or long, slow shaking, near the coast, don't wait for a warning. Move away from the sea to high ground right away. This guide walks through each step in the order you'd face it, with the reasons and sources, plus what travelers need to know about earthquakes in Japan.

1. While the ground is shaking

In strong shaking it's hard to walk, let alone run. Get low and protect your head with your bag or arms. Keep away from windows, signs and eaves, vending machines and block walls. Japanese streets have many concrete block walls and vending machines, and falling or toppling objects cause many injuries (Korea's national disaster safety portal; Japan's Cabinet Office). As soon as the shaking stops, go straight to the next step.

2. When the shaking stops: don't wait for the warning

JMA aims to issue tsunami warnings within about 3 minutes of an earthquake. But if the epicenter is close, the wave can arrive before the warning. Shizuoka Prefecture's 4th earthquake damage estimate says that in a Nankai Trough megaquake, water 50 cm high could reach the coast of Shimizu Ward in Shizuoka City in as little as 2 minutes. So if you feel strong shaking, or shaking that lasts close to a minute, near the coast, the shaking itself is your warning.

• Evacuate first, check later. The minute or two you spend on news or social media is the time you needed to climb the stairs.
• Your life before your luggage. Don't go back to your room for bags or your passport. Your embassy or consulate can issue a new passport.
• Tendenko (everyone evacuates on their own). Don't wait for family or coworkers; each person heads straight for high ground. Agree in advance to “evacuate separately and meet at the top” so nobody goes back down to look for anyone (Cabinet Office disaster-prevention magazine Bousai).

3. Where to go: high, not far

When time is short, go to a nearby tall building instead of distant high ground (“tooku yori takaku,” higher rather than farther: Aichi Prefecture's five disaster-prevention points; Cabinet Office). Coastal towns far from hills designate tsunami evacuation buildings and towers.

• Look for the green pictogram sign. A green sign showing a wave and a person climbing stairs marks a tsunami evacuation building or area (JIS Z 8210). You can find it even if you can't read Japanese.
• At least the floor shown on the sign, ideally the roof. Evacuation buildings designate floors above the expected flood height. Don't trust anyone who says the 2nd floor is enough.
• If the water rises, go up one more floor. It can come higher than expected (JMA).
• An emergency evacuation site is not the same as a shelter. A designated emergency evacuation site (指定緊急避難場所) is where you go to save your life right now; a designated shelter (指定避難所, usually a school) is where you stay afterward. If the first wave is minutes away, go to the nearby evacuation building or tower, not the distant shelter.

4. How to get there: on foot, avoiding bridges and rivers

• Evacuate on foot as a rule. Cars get stuck in traffic, dead traffic lights and damaged roads, and a few tens of centimeters of water can float them away (Cabinet Office; Shizuoka City plan). Don't go looking for your rental car.
• Stay away from bridges and riverbanks. A tsunami surges up bays and rivers and gets even higher (JMA).
• Follow the locals. Even if you can't understand the announcements, if people around you are heading for high ground, go with them. Streets blocked by collapsed walls won't show up in your map app right away.
• Help people who can't move on their own (older people, people with disabilities, children) and bring them with you, but your own safety comes first. Never go into the water to rescue someone; reach out from high ground with a hand, a pole or a rope (Korea Fire Agency water-rescue guidance).

5. Never go to look at the sea

Even if the water pulls back, never go toward the sea. Tsunamis don't always start with the sea receding, but a sudden drop in the water can be a sign that a big wave is coming. Seawalls and piers are the first places the water goes over. Don't stop to watch or film the wave.

A tsunami is not like an ordinary wave. It's a whole wall of sea moving inland, so even a 20–30 cm tsunami can knock you down and sweep you away. Even in water about 10 m deep it moves at around 36 km/h, so if you wait until you see it, it will catch you (JMA).

6. Stay on high ground until the all-clear

Tsunamis come in repeated waves, and later waves can be bigger than the first. A large wave can arrive hours later. Don't come down until the warning or advisory is lifted (JMA).

• Japan's three tsunami alert levels: Major Tsunami Warning (大津波警報, expected height over 3 m), Tsunami Warning (津波警報, 1–3 m) and Tsunami Advisory (津波注意報, 0.2–1 m). For a megaquake above magnitude 8, the first bulletin says “huge” (巨大) or “high” (高い) instead of a number. Even if a number looks small, evacuate right away.
• Check “the warning's been lifted” rumors against official sources. If you follow a viral video or group-chat rumor back down, you're exposed to the next wave.
• Wet clothes lead to hypothermia. Take off wet clothing, wrap up in something dry or a blanket, and huddle together. Alcohol makes you lose heat faster. Don't rub the arms and legs of someone with severe hypothermia; warm the trunk first, slowly (Korea Fire Agency first-aid guidance).
• Text instead of calling, and save your battery. Phone lines jam right after a disaster.
• Don't rush back into ground floors after the all-clear. Flooded buildings are full of mud, nails and broken doors. Go to the designated shelter and register so family searches and support can reach you.

7. If an earthquake hits while you're traveling in Japan

Preparing for an earthquake in Japan takes ten minutes before your trip. The hardest part for foreign travelers is language.

• Install the Safety tips app. This free app from the Japan Tourism Agency (promoted by JNTO) pushes earthquake early warnings and tsunami warnings in English and other languages, with evacuation flowcharts and communication cards. The NHK WORLD-JAPAN app also carries disaster news in many languages.
• Know how warnings reach you. TV, radio, emergency phone alerts, city loudspeakers announcing “ōtsunami keihō (major tsunami warning)… takai tokoro e (to high ground)”, sirens, and the red-and-white checkered tsunami flag at beaches all mean “evacuate now” (JMA).
• When you check in, look at the hazard map and the nearest high place. If you're staying by the sea, find out whether your hotel is an evacuation building and from which floor up.
• Emergency numbers in Japan: 119 (fire and ambulance), 110 (police). Register your trip with your country's embassy or travel-advisory service and keep its emergency number handy; Korean travelers can call the consular call center at +82-2-3210-0404 (24 hours).

8. On other coasts, too

The same rules apply on any coast. Korea's east coast, for example, was hit by tsunamis from large earthquakes in the sea west of Japan in 1983 and 1993, and Korea's national disaster safety portal gives the same core advice: if you feel shaking on the coast or hear a tsunami warning, evacuate to high ground immediately. Wherever you are, learn the local tsunami evacuation signs and routes, and follow your local authorities' alerts.

Keep at least three days of emergency supplies

For days after a tsunami, power, water and phone service can be cut, and shops can close. In October 2026 the Japanese government (with the launch of its new Disaster Management Agency) and the UK government (in its Be Ready campaign) again urged every household to keep at least three days, and ideally a week, of water and food. Korea's national disaster safety portal checklist points the same way.

• Water: about 3 L per person per day × at least 3 days.
• Food: canned food, ready-to-eat rice and energy bars that need no cooking.
• Portable toilet, plastic bags and wet wipes.
• Flashlight, power bank, portable radio and spare batteries.
• Medicines, masks, a (foil) blanket, some cash and a copy of your ID.

When traveling, a small bag with a power bank, a bottle of water, your medicines and a copy of your passport makes a big difference. When you evacuate, take that one bag, or just yourself.

Practice with a simulation

Reading a list is easy. Remembering it while the ground rolls and a loudspeaker blares in a language you don't understand is not. Shizuoka Tsunami: 5 Minutes to the First Wave is a free browser game where you make these decisions against the clock from Miho Beach, a hotel lobby or a harbor shopping street (the quake, characters and hotel are fictional). See the game guide.

Sources

• Japan Meteorological Agency (JMA): “Protecting yourself from tsunamis” (津波から身を守るために), tsunami warning and advisory explanations, tsunami flag guidance
• Cabinet Office of Japan (Disaster Management): tsunami evacuation guidance, Bousai magazine (tsunami tendenko), disaster-type evacuation pictograms (JIS Z 8210)
• Shizuoka Prefecture: 4th Earthquake Damage Estimate (Nankai Trough megaquake)
• Shizuoka City: tsunami disaster-prevention community plan and tsunami evacuation building program
• Aichi Prefecture: five disaster-prevention points (higher rather than farther)
• Japan Tourism Agency / JNTO: Safety tips
• Ministry of the Interior and Safety (Korea): national disaster safety portal, tsunami guidance
• Ministry of Foreign Affairs (Korea): overseas travel safety and consular call center
• Korea Fire Agency: first aid and water-rescue guidance

This article is general educational information, not official emergency guidance. In a real emergency, follow the local tsunami hazard map and instructions from the government and local authorities.

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▶ PLAY: SHIZUOKA TSUNAMI, 5 MINUTES TO THE FIRST WAVE