Tsunami

What is a Tsunami?

A tsunami is one of the most powerful and destructive natural forces. It is a series of extremely long waves (multiple waves tens-to-hundreds of miles between crests) caused by a large and sudden displacement of the ocean. Tsunamis radiate outward in all directions from the point of origin and can move across entire ocean basins. When they reach the coast, they can cause dangerous coastal flooding and powerful currents that can last for several hours or days.

Before a Tsunami: Preparedness Tips

Although tsunamis cannot be prevented, there are things you can do before a tsunami that could save your life and the lives of your family and friends. Importantly, find out if your home, school, workplace, or other places you visit often are in a tsunami hazard zone.

If you live or spend time in a tsunami hazard zone:

  • Educate yourself about tsunami warnings (official and natural) and ensure you have multiple ways to receive official warnings. In the United States, get a NOAA Weather Radio, sign up for text message alerts from your local government, and verify that your mobile devices receive wireless emergency alerts.
  • Make an emergency plan that includes plans for family communication and evacuation.
  • Map out routes from home, work, and other places you visit often to safe places on high ground or inland (away from the water) and outside the tsunami hazard zone. Your community may already have identified evacuation routes and assembly areas (if they have not, identify a safe place at least 100 feet above sea level or 1 mile inland). Plan to evacuate on foot if you can; roads may be impassable due to damage, closures, or traffic jams.
  • Practice walking your routes, even in darkness and bad weather. This will ease evacuation during an emergency.
  • Put together a portable disaster supplies kit with items you and your family (including pets) may need in an emergency. Prepare kits for work and cars, too.
  • Be a role model. Share your knowledge and plans with others.
  • If you have children in school in a tsunami hazard zone, find out the school’s plans for evacuating and keeping children safe. If you are visiting the coast, find out about local tsunami safety. Your hotel or campground should have this information.

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Staying Safe: During an Emergency

How will I know that a tsunami is coming?

There are two ways that you may be warned that a tsunami is coming: an official tsunami warning and a natural tsunami warning. Both are equally important. You may not get both.

  • In the United States, an official tsunami warning will be broadcast through local radio and television, marine radio, wireless emergency alerts, NOAA Weather Radio, and NOAA websites (like Tsunami.gov) and social media accounts (Facebook and Twitter). It may also come through outdoor sirens, local officials, emails and text message alerts from state and local opt-in systems, and telephone notifications.
  • There may not always be time to wait for an official tsunami warning. A natural tsunami warning may be your first, best, or only warning that a tsunami is on its way. Natural tsunami warnings include strong or long earthquakes, a loud roar (like a train or an airplane) from the ocean, and unusual ocean behavior. The ocean could look like a fast- rising flood or a wall of water (bore). Or, it could recede suddenly, showing the ocean floor, reefs, and fish like a very low, low tide. If you experience any of these warnings, even just one, a tsunami could be coming.

How should I respond to a tsunami?

How you should respond to a tsunami warning depends on where you are and the type of warning you receive (i.e., official or natural). Be prepared to respond immediately to whatever you hear or see first.

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ASHORE

If you are in a tsunami hazard zone and receive an official tsunami warning:

  • Stay out of the water and away from beaches and waterways.
  • Get more information from radio, television, or your mobile device (text or data) and continue to stay informed throughout the event.
  • If officials ask you to evacuate, implement your emergency plan and move quickly to your safe place. If you do not have a safe place or cannot reach it, follow evacuation signs to safety or go as high or as far inland (away from the water) as possible (at least 100 feet above sea level or a mile inland).

If you are in a tsunami hazard zone and receive a natural tsunami warning, a tsunami could arrive within minutes:

  • In case of an earthquake, protect yourself. Drop, cover, and hold on. Be prepared for aftershocks. Each time the earth shakes, drop, cover, and hold on.
  • Take action. Do not wait for an official warning or instructions from officials.
  • As soon as you can move safely, implement your emergency plan and move quickly to your safe place. If you do not have a safe place or cannot reach it, follow evacuation signs to safety or go as high or as far inland (away from the water) as possible (at least 100 feet above sea level or a mile inland).
  • If there is earthquake damage, avoid fallen power lines and stay away from weakened structures.
  • When you are in a safe place, get more information from radio, television, or your mobile device (text or data).

If you are on the beach or near water and feel an earthquake of any size and length, move quickly to high ground or inland (away from the water) as soon as you can move safely. Get more information from radio, television, or your mobile device (text or data).

If you are outside of the tsunami hazard zone and receive a warning, stay where you are unless officials tell you otherwise.

AT SEA

If you are on a boat and you get a tsunami warning, your response will depend largely on where you are.

In the United States, in general, it is recommended that:

  • If you are in a harbor and get a tsunami warning, you should leave your boat and move quickly to a safe place on land (high ground or inland, away from the water).
  • If you are at sea and get a tsunami warning, you should move to a safe depth* and stay away from harbors under warning until officials tell you the threat has passed.

*Safe depths vary by region, but the minimum safe depth is 30 fathoms (180 feet). Your harbor master, port captain, the U.S. Coast Guard, and local and state emergency management offices are the best sources for safe depth and other tsunami safety information and regulations for boaters in your area.

If you are a boat owner or captain, take extra steps to prepare for a tsunami:

  • Make sure you have a way to receive tsunami warnings when you are on the water. The U.S. Coast Guard will issue urgent marine information broadcasts on your marine VHF radio’s channel 16. Additional information will be available from NOAA Weather Radio.
  • Make a plan and put together a disaster supplies kit to keep on board your boat. Be aware that shore facilities may be damaged, so if you are at sea during a tsunami, you may not be able to return to the harbor you left. Be prepared to remain at sea for a day or more.

For your safety and others, always follow instructions from local officials and stay out of the tsunami hazard zone until they tell you it is safe. In the United States, to find out if you are in a tsunami hazard zone, visit the California Department of Conservation Tsunami Maps & Data Page.

Visit the NWS Tsunami Safety and International Tsunami Information Center websites to learn more.

Staying Safe: After a Tsunami

After a tsunami, local officials will assess the damage and tell you when it is safe to return. Even though the danger of the tsunami has passed, other dangers may remain. If there is a lot of damage, it may be days before it is safe to return (or before you are allowed to return) to affected areas.

  • Stay out of the tsunami hazard or evacuation zone until local officials tell you it is safe. The cancellation of a tsunami warning does not mean the danger has passed.
  • Follow instructions from local officials. It is their job to keep you safe.
  • Stay away from areas that have been damaged for your own safety and so emergency responders can have full access.
  • Stay out of any building that has earthquake or tsunami damage or has water around it until a professional or local official tells you it is safe to enter.
  • Avoid fallen power lines or broken utility lines and report those that you see.

More safety information about returning home after a disaster is available from the Federal Emergency Management Agency.

  • Keep listening to NOAA Weather Radio or local radio or television or using your mobile device (text or data) to get the latest updates about when it is safe to return, areas to avoid, the location of shelters (if available) and important safety instructions. Limit non-emergency phone calls to keep the lines open for emergency communications.

  • Let your close friends and loved ones know that you are okay. The American Red Cross’s Safe and Well website can help you do this. You can also use the website to find out if others have registered themselves as safe and well.

Los Angeles County residents and business owners, including persons with disabilities and others with access and functional needs may call 211 LA County for emergency preparedness information and other referral services. The toll-free 2-1-1 number is available 24 hours a day, seven days a week. 211 LA County services can also be accessed online by visiting www.211la.org.