Lesson · Coastal & Marine Hazard Dynamics

Natural Tsunami Warnings and Immediate Response

Why a near-field tsunami arrives before any official warning can, which natural signs constitute the warning themselves, and why the first wave is rarely the largest.

  • General Public
  • Teacher
  • Student
  • Visitor
  • Responder

Learning objectives

  • Identify the three natural tsunami warnings: strong shaking, sudden sea withdrawal, and a loud roar.
  • Explain why a near-field tsunami leaves no time for an official bulletin.
  • Describe why the first wave is often not the largest and why the sequence lasts hours.
  • State the vertical and horizontal evacuation targets for your own stretch of coast.

In the field

Ordered, and meant to be workable under pressure. Numbered because the sequence matters.

  1. Treat strong or long shaking near the coast as the warning itself and move immediately.
  2. Move inland and upslope on foot; roads jam and vehicles become traps.
  3. Aim for high ground rather than a fixed distance, and keep going past the first rise.
  4. Do not return to the shore for at least several hours, and only when authorities declare it clear.
  5. Walk the evacuation route to high ground once, in daylight, before you ever need it.

Sources · 3

The tag under each source states what was actually checked. “Authority named · URL not re-resolved” means the issuing body and document are named, but the link was not re-resolved for this lesson. It is not a claim of verification, and the authority’s own current bulletin always supersedes anything here.