Tsunamis are a series of large ocean waves generated by major earthquakes beneath the ocean floor or major landslides into the ocean. When the waves enter shallow water, they may rise to several feet or, in rare cases, tens of feet, striking the coast with devastating force. People on the beach or in low coastal areas need to be aware that a tsunami could arrive within minutes after a severe earthquake. The tsunami danger period can continue for many hours after a major earthquake. A tsunami can occur during any season of the year and at any time, day or night.
- A strong earthquake lasting 20 seconds or more near the coast.
- A noticeable rapid rise or fall in coastal waters.
The International Tsunami Warning System monitors ocean waves after any Pacific earthquake with a magnitude greater than 6.5. If waves are detected, warnings are issued to local authorities who can order the evacuation of low-lying areas if necessary.
The National Oceanic and Atmospheric Administration (NOAA)’s National Weather Service operates two tsunami warning centers:
- West Coast/Alaska Tsunami Warning Center (WC/ATWC), Palmer, Alaska. Serves Alaska, Washington, Oregon, California, the U.S. Atlantic and Gulf of Mexico coasts, Puerto Rico, the U.S. Virgin Islands and Canada.
- Pacific Tsunami Warning Center (PTWC), Ewa Beach, Hawaii. Serves Hawaii and the U.S. Pacific territories, and as an international warning center for the Pacific and Indian oceans and the Caribbean Sea.
- Find out if your home, school, workplace or other frequently visited locations are in tsunami hazard areas.
- 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.
- Plan evacuation routes from your home, school, workplace and other places you could be where tsunamis present a risk. If possible, 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. You should be able to reach your safe location on foot within 15 minutes.
- Find out what the school evacuation plan is. Find out if the plan requires you to pick your children up from school or from another location. Telephone lines during a tsunami watch or warning may be overloaded, and routes to and from schools may be jammed.
- Practice your evacuation routes. Familiarity may save your life. Be able to follow your escape route at night and during inclement weather. Practicing your tsunami survival plan makes the appropriate response more of a reaction, requiring less thinking during an actual emergency.
- 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.
- Drop, cover and hold on. You should first protect yourself from the earthquake.
- When the shaking stops, gather members of your household and move quickly to higher ground away from the coast. A tsunami may be coming within minutes.
- Avoid downed power lines and stay away from buildings and bridges from which heavy objects might fall during an aftershock.
- Use a NOAA Weather Radio or tune to a Coast Guard emergency frequency station or a local radio or television station for updated emergency information.
- Locate household members and review evacuation plans. Be ready to move quickly if a tsunami warning is issued.
- If you hear an official tsunami warning or detect signs of a tsunami, evacuate at once.
- Take your emergency preparedness kit. Having supplies will make you more comfortable during the evacuation.
- Take your pets with you. If it is not safe for you, it’s not safe for them.
- Get to higher ground as far inland as possible. Watching a tsunami could put you in grave danger. If you can see the wave, you are too close to escape it.
- Continue using a NOAA Weather Radio or tuning to a Coast Guard station or a local radio or television station for the latest updates.
- 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.
- 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 disabilities and large families who may need additional help in an emergency situation.
- Avoid disaster areas. Your presence might interfere with emergency response operations and put you at further risk from the residual effects of floods.
- Use the telephone only for emergency calls.
- 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.
- Watch animals closely and keep them under your direct control.