Tsunamis, also known as seismic sea waves (mistakenly called "tidal waves"), are a series of enormous waves created by an underwater disturbance, such as an earthquake, landslide, meteorite, or volcanic activity. 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.
Earthquake-induced movement of the ocean floor most often generates tsunamis. If a major earthquake or landslide occurs close to shore, the first wave in a series could reach the beach in a few minutes, before a warning can be issued. Areas are at greater risk if they are less than 25 feet above sea level and within a mile of the shoreline.
Tsunami waves can be very destructive. Other hazards include flooding, contamination of drinking water, and fires from ruptured gas lines or tanks. A tsunami can strike anywhere along most of the U.S. coastline. The most destructive tsunamis have occurred along the coasts of California, Oregon, Washington, Alaska, and Hawaii.
During a Tsunami:
- Turn on your radio to learn if there is a tsunami warning if an earthquake occurs and you are in a coastal area.
- Move inland to higher ground immediately and stay there. If there is no high ground, find a strong, multi-story structure, like a parking garage, and go to the highest level.
- CAUTION - If there is noticeable recession in water away from the shoreline this is nature's tsunami warning. Move away from the shore immediately.
After a Tsunami:
- Stay away from flooded and damaged areas until officials say it is safe to return.
- Stay away from debris in the water; it may pose a safety hazard to boats and people.