Prepping for a tsunami (Part 2): The warning signs
The lifeguard who survived the 2004 wave in Southeast Asia learned the warning sign from a ten-year-old. The sea pulled back, the boats were left sitting on wet sand, and the tourists walked out to look. A girl on the beach started screaming the word her schoolteacher had taught her weeks earlier, a word she had learned in a two-minute geography lesson about a place she had never been. Her family ran. Dozens of people followed them because she screamed. The tourists who kept walking out to photograph the fish did not come back. One lesson, taught once, cleared a beach.
The ocean itself gives you a warning, if you know how to read it. The sudden recession of the sea, a loud roar from offshore, or a strong earthquake near the coast are all signals that a tsunami may be minutes away.
Caution: The “Official Warning” trap. In a local tsunami, the official warning may not arrive in time. The earthquake IS the warning. If you feel strong shaking near the coast, do not wait for a siren, move to high ground immediately.
Disclaimer: The information provided in this article is for general informational and educational purposes only. It is not intended as, and should not be considered, professional or emergency-response advice. Always follow the instructions of local authorities and tsunami warning centers.
The Readiness Audit
Would you recognize a tsunami warning if you saw one?
- Green: You know the three natural warning signs, receding water, strong shaking, and a loud roar, and you’d act on any of them immediately.
- Yellow: You’d wait for an official siren or alert before doing anything.
- Red: You’d walk down to the beach to look at the receding water.
If you are Yellow or Red, execute Phase 1 immediately.
Phase 1: The Receding Sea (The Classic Sign)
Goal: Recognize the most famous, and most deadly, warning sign.
When a tsunami approaches, the trough of the wave often arrives first, pulling the water dramatically away from the shore.
- The sign: the ocean suddenly recedes, exposing the seafloor, stranded fish, and rocks that are normally underwater.
- The trap: this is fascinating, and people walk down to look. This is exactly how people die. The water that receded is about to come back as a wall.
- The action: if you see the water pull back dramatically, a tsunami is coming. You have minutes. Run to high ground immediately.
The Takeaway: Receding water is not a curiosity. It is a countdown. When you see it, you run.
Phase 2: The Earthquake (The First Warning)
Goal: Understand that the shaking is the warning.
In a local tsunami, the earthquake that triggers the wave is your first and most reliable warning.
- The sign: strong ground shaking near the coast, shaking that makes it hard to stand, lasting 20 seconds or more.
- The action: drop, cover, and hold on during the shaking. The moment it stops, move to high ground on foot. Do not wait for an official alert.
- The reason: the tsunami may arrive in minutes. The official warning may not come in time. The earthquake is the warning.
The Takeaway: If you feel strong shaking near the coast, the clock has already started. Move to high ground the moment the shaking stops.
Phase 3: The Roar (The Audible Sign)
Goal: Recognize the sound of an approaching tsunami.
A tsunami makes a distinctive sound as it approaches, a sound survivors consistently describe.
- The sign: a loud roar, like a freight train or a jet engine, coming from offshore.
- The action: if you hear it, the wave is close. Move to high ground immediately. There is no time to investigate.
- The reason: by the time you can hear the roar, the wave is nearly on top of you.
The Takeaway: A roar from the ocean is not the wind. It is the wave. Run.
Phase 4: The Official Warning (The Backup)
Goal: Understand the role of official alerts.
Official tsunami warnings are valuable, but they are a backup, not a primary defense.
- The system: tsunami warning centers monitor earthquakes and issue alerts via sirens, radio, TV, and Wireless Emergency Alerts.
- The limit: in a local tsunami, the official warning may arrive after the wave. The natural signs are faster.
- The rule: treat official warnings as confirmation, not as your only trigger. The natural signs, shaking, receding water, the roar, are your primary triggers.
The Takeaway: Official warnings are a safety net. The natural signs are your first line of defense.
The Essential Kit Checklist
- The knowledge: teach every family member the three natural warning signs.
- The drill: practice the response, “if the ground shakes, we move to high ground.”
- The route: confirm your evacuation route and walk it once this season.
- The alerts: enable Wireless Emergency Alerts on your phone.
Scenario Planner (Contingencies)
“The water receded and everyone is walking out to look.” The trap: following the crowd toward the danger. The fix: be the one who runs the other way. Receding water is a countdown, not a spectacle. Move to high ground and warn others as you go.
“I felt shaking, but it was mild, so I stayed put.” The trap: underestimating a mild quake. The fix: even moderate shaking can trigger a tsunami if it’s offshore and long-duration. If you’re near the coast and feel shaking that lasts 20 seconds or more, evacuate. It’s better to be wrong on high ground than right at sea level.
Next Steps
- Enable Wireless Emergency Alerts on every phone in the house tonight, and say the three natural signs out loud at dinner, because the ten-year-old who knows the signs can clear a beach.
- Rewrite your family rule in one sentence (“if the ground shakes hard or long, we walk uphill”) and tape it inside a kitchen cabinet.
- Read Part 3: The evacuation next, for the foot race to high ground and the routes that get you there.
Originally adapted from public NOAA tsunami guidance (public domain).