Never turn your back on the ocean least it swallow you up. - The Sailor

Tsunamis, also known as seismic sea waves, are a series of enormous waves created by an underwater disturbance such as an earthquake, landslide, volcanic eruption, or meteorite. A tsunami can move hundreds of miles per hour in the open ocean and smash into land with waves as high as 100 feet or more. Once the wave approaches the shore, it builds in height. The topography of the coastline and the ocean floor will influence the size of the wave. There may be more than one wave and the succeeding one may be larger than the one before. That is why a small tsunami at one beach can be a giant wave a few miles away.

Except for the largest tsunamis, most tsunamis do not result in giant breaking waves. Rather, they come in much like very strong and fast-moving tides (i.e., strong surges and rapid changes in sea level).

Areas are at greater risk if they are less than 25 feet above sea level and within a mile of the shoreline. Drowning is the most common cause of death associated with a tsunami. Tsunami waves and the receding water are very destructive to structures in the run-up zone. Other hazards include flooding, contamination of drinking water, and fires from gas lines or ruptured tanks.


  • Advisory - An earthquake has occurred in the Pacific basin, which might generate a tsunami and produce strong currents or waves dangerous to those in or near the water.
  • Watch - A tsunami was or may have been generated, but is at least two hours travel time to the area in watch status.
  • Warning - A potential tsunami with significant widespread inundation is imminent or expected.
  • Drawback - the first part of a tsunami to reach land is a trough called a drawback rather than a wave crest, the water along the shoreline recedes dramatically, exposing normally submerged areas.
  • Run-up - When the crest of the wave hits, sea level rises (called run-up). Run-up is usually expressed in meters above normal high tide.

Before a Tsunami

  • To begin preparing, you should build an emergency kit and make a family communications plan.
  • Know the height of your street above sea level and the distance of your street from the coast or other high-risk waters. Evacuation orders may be based on these numbers.
  • If you are a tourist, familiarize yourself with local tsunami evacuation protocols. You may be able to safely evacuate to the third floor and higher in reinforced concrete hotel structures.

During a Tsunami

  • Follow the evacuation order issued by authorities and evacuate immediately. Take your animals with you.
  • Move inland to higher ground immediately. Pick areas 100 feet (30 meters) above sea level or go as far as 2 miles (3 kilometers) inland, away from the coastline. If you cannot get this high or far, go as high or far as you can. Every foot inland or upward may make a difference.
  • Stay away from the beach. Never go down to the beach to watch a tsunami come in. If you can see the wave you are too close to escape it.

After a Tsunami

  • Listen to a battery-operated radio or television for the latest emergency information.
  • Return home only after local officials tell you it is safe. A tsunami is a series of waves that may continue for hours. Do not assume that after one wave the danger is over. The next wave may be larger than the first one.
  • Avoid disaster areas. Your presence might interfere with emergency response operations and put you at further risk from the residual effects of floods.