A tsunami (pronounced soo-ná-mees) is a series of ocean waves generated by an underwater disturbance such as an earthquake or landslide. In the deep ocean, the tsunami wave may only be a few inches high. The tsunami wave may come gently ashore or may increase in height to become a fast moving wall of turbulent water several feet high.
If a major earthquake or landslide occurs close to shore, the first wave in a series could reach the beach in a few minutes, even before a warning is issued.
Although a tsunami cannot be prevented, the impact of a tsunami can be lessened through community preparedness, timely warnings, and effective response.
Read about Japan tsunami marine debris
What to do before a tsunami
The following are things you can do to protect yourself, your family and your property from the effects of a tsunami:
- Identify your local tsunami hazard zones and routes by visiting the Oregon Department of Geology and Mineral Industries Oregon Tsunami Clearinghouse.
Here you can find:
What to do during a tsunami
Listen to local officials - Learn about the emergency plans that have been established in your area by your state and local government. In any emergency, always listen to the instructions given by local emergency management officials.
Local and distant tsunamis
Local tsunamis - A local tsunami can come onshore within 15 to 20 minutes after the earthquake - before there is time for an official warning from the national warning system. Ground shaking from the earthquake may be the only warning you have. Evacuate quickly!
Distant tsunamis - A distant tsunami will take 4 hours or more to come ashore. You will feel no earthquake, and the tsunami will generally be smaller than that from a local earthquake. Typically, there is time for an official warning and evacuation to safety.
Evacuation for a distant tsunami will generally be indicated by a 3-minute siren blast (if your area has sirens) and an announcement over NOAA weather radio that the local area has been put into an official TSUNAMI WARNING. In isolated areas along beaches and bays you may not hear a warning siren. Here, a sudden change of sea level should prompt you to move immediately to high ground. If you hear the 3-minute blast or see a sudden sea level change, first evacuate away from shoreline areas, then turn on your local broadcast media or NOAA weather radio for more information.
We distinguish between a tsunami caused by an undersea earthquake near the Oregon coast (a local tsunami) and an undersea earthquake for away from the coast (a distant tsunami).
What to do for both local and distant tsunamis
- Evacuate on foot, if at all possible. Follow evacuation signs and arrows to an Assembly Area. If your immediate safety is not at risk, take your animals with you.
- If you need help evacuating, tie something white (sheet or towel) to the front door knob. Make it large enough to be visible from the street. If the emergency is a distant tsunami, then help may arrive. In the event of a local tsunami, it is unlikely that anyone will help you, so make a plan and be prepared!
- Stay away from potentially hazardous areas until you receive an ALL CLEAR from local officials. Tsunamis often follow river channels, and dangerous waves can persist for several hours. Local officials must inspect all flooded or earthquake-damaged structures before anyone can go back into them.
- After evacuations, check with local emergency officials if you think you have special skills and can help, or if you need assistance locating lost family members.
What to do after a tsunami
- 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.
- Go to a designated public shelter if you have been told to evacuate or you feel it is unsafe to remain in your home. Text SHELTER plus your ZIP code to 43362 (4FEMA) to find the nearest shelter in your area (example: shelter 12345).
- Avoid disaster areas. Your presence might interfere with emergency response operations and put you at further risk from the residual effects of floods.
- Stay away from debris in the water; it may pose a safety hazard to people or pets.
- Check yourself for injuries and get first aid as needed before helping injured or trapped persons.
- If someone needs to be rescued, call professionals with the right equipment to help. Many people have been killed or injured trying to rescue others.
- Help people who require special assistance - infants, elderly people, those without transportation, people with access and functional needs and large families who may need additional help in an emergency situation.
- Continue using a NOAA Weather Radio or tuning to a Coast Guard station or a local radio or television station for the latest updates.
- Stay out of any building that has water around it. Tsunami water can cause floors to crack or walls to collapse.
- Use caution when re-entering buildings or homes. Tsunami-driven floodwater may have damaged buildings where you least expect it. Carefully watch every step you take.
- To avoid injury, wear protective clothing and be cautious when cleaning up.
Find additional information on how to plan and prepare for a tsunami and learn about available resources by visiting the following websites: