Tsunamis, also known as seismic sea waves, are most common along the Pacific coast, but can strike anywhere along the U.S. coastlines. According to Your Survival Tsunami expert Stephanie Fritts, Pacific County Director of Communications and Emergency Management, “any area where volcanic or earthquake activity interfaces with an ocean or large bay is at risk.” These shifts are usually caused by earthquakes, but can also be caused by undersea landslides or slumps, volcanoes, or even meteor impacts. In deep ocean waters, the waves can travel hundreds of miles an hour with little surface indication. However, as the waves approach land, the shallow waters cause them to slow down and build up, sometimes to very significant heights. The December 2004 tsunami Sumatra had reports of wave heights as high as 60 feet. Wave heights of 100 feet have even been recorded in Japan in prior tsunami events throughout history. The waves can radiate out in all directions from the epicenter, and can travel great distances.

Know the Key Terms

AdvisoryAn earthquake has occurred which might generate a tsunami.

WatchA tsunami was or may have been generated, but is at least two hours travel time to the area in Watch status.

WarningA tsunami was, or may have been generated, which could cause damage; therefore, people in the warned area are strongly advised to evacuate.

How to Prepare

Develop a Family Disaster Plan.Tsunami-specific planning should include the following:

Learn about tsunami risk in your community. Contact your local emergency management office or American Red Cross chapter, to find out if your home, school, workplace or other frequently visited locations are in tsunami hazard areas. It is important to know the height of your street above sea level and the distance of your street from the coast or other high-risk waters.

If you are visiting an area at risk from tsunamis, check with the hotel, motel, or campground operators for tsunami evacuation information and how you would be warned. It is important to know designated escape routes before a warning is issued.

If you are at risk from tsunamis:Plan an evacuation route. If possible, pick an area 100 feet above sea level or go up to two miles inland, away from the coastline. If you can't get this high or far, go as high as you can. Every foot inland or upwards makes a difference. You should be able to reach your safe location on foot within 15 minutes.

Practice your evacuation route. Familiarity may save your life. Be able to follow your escape route at night and during inclement weather. Practicing your plan makes the appropriate response more of a reaction, requiring less thinking during an actual emergency situation.

Listen to a NOAA Weather Radio. A radio with a tone-alert feature to keep you informed of local watches and warnings. The tone alert feature will warn you of potential danger even if you are not currently listening to local radio or television stations.

Talk to your insurance agent. Many homeowners' policies do not cover flooding from a tsunami. Ask about the National Flood Insurance Program.

Discuss tsunami with your family. Everyone should know what to do in case all family members are not together. Discussing tsunamis ahead of time will help reduce fear and anxiety, and let everyone know how to respond.

How to Protect Your Property

Avoid building or living in buildings within several hundred feet of the coastline. These areas are more likely to experience damage from tsunamis, strong winds, or coastal storms.

Make a list of items to bring inside in the event of a tsunami. A list will help you remember anything that can be swept away by tsunami waters.

Elevate coastal homes. Most tsunami waves are less than 10 feet. Elevating your house will help reduce damage to your property from most tsunamis. This list should include items like children's toys, potted plants and lawn chairs.

Follow flood preparedness precautions. Tsunamis are large amounts of water that crash onto the coastline, creating floods.

Have an engineer check your home and advise about ways to make it more resistant to tsunami water. There may be ways to divert waves away from your property. Improperly built walls could make your situation worse. Consult with a professional for advice.

Tidal Waves vs. Tsunami Waves

Throughout history, people have often confused tsunami waves and tidal waves. However, these two types of waves are in fact very different.  Although a tsunami's impact upon a coastline is dependent upon the tidal level at the time a tsunami strikes, tsunamis are unrelated to the tides. Tides result from the unbalanced, extraterrestrial, gravitational influences of the moon, sun, and planets. Unlike tidal waves or wind-generated waves, tsunami's have long wavelengths which come ashore more like a flood wave, rather than the breaking surf usually seen generated from wind and tidal waves.