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Tsunamis are among Earth's rarest hazards. But, even though tsunamis do not occur very often, and most are small and nondestructive, they pose a major threat to coastal communities, particularly in the Pacific. A tsunami can strike any ocean coast at any time. There is no season for tsunamis. We cannot predict where, when or how destructive the next tsunami will be. However, while tsunamis cannot be prevented, there are things you can do before, during and after a tsunami that could save your life and the lives of your family and friends. Read these pages to learn about tsunamis and what you can do to keep yourself and your loved ones safe in the event of a tsunami.

A tsunami is one the most powerful and destructive natural forces. It is a series of waves (not just one) caused by a large and sudden disturbance of the sea. Tsunami waves radiate outward in all directions from the disturbance and can move across entire ocean basins. Most tsunamis are caused by undersea earthquakes, but can also be caused by landslides, volcanic activity, certain weather-related phenomena and meteorites. Not all earthquakes cause tsunamis.

Tsunami Risk

Tsunamis are among the rarest of Earth's natural hazards. Each year, there are approximately two tsunamis that cause damage near their source. Destructive, ocean-wide tsunamis are more infrequent.

Tsunamis can strike any U.S. coastline, but the risk is greatest to coasts that border the Pacific. Low-lying coastal areas such as beaches, bays, lagoons, harbors and river mouths and areas along rivers and streams that lead to the ocean are at greatest risk. Tsunami waves can wrap around headlands, islands and sand spits, so coasts facing away from the tsunami source may also be at risk. Like earthquakes, tsunamis can happen at any time of the day or night, during any kind of weather and in all seasons.

Local, Regional and Distant Tsunamis

Tsunamis may be local, regional or distant. The type of tsunami depends on the location of the source of the tsunami and where it may strike land.

  • Local tsunami: The source of a local tsunami is close to the coast. It may reach the coast in less than one hour. There may not be time for an official tsunami warning, and you may only have a few minutes to get to safety. Since tsunamis are usually most dangerous near their source, it is important to recognize and respond to natural tsunami warnings, could be your only warning.
  • Regional tsunami: The source of a regional tsunami is generally between 60 and 600 miles away. Once generated, it takes a regional tsunami between one and three hours to reach the shore. There is time for NWS to issue an official tsunami warning. You should have a little more time to get to safety if told to do so. You may or may not feel the earthquake.
  • Distant tsunami: The source of a distant tsunami is far away, generally more than 600 miles away. Once generated, it takes a distant tsunami three or more hours to reach the shore. There is time for an official tsunami warning to be issued. You should have enough time to evacuate to a safe place if necessary.

What may be a local tsunami in one location may be a regional or distant tsunami in another. For example:

  • If an earthquake off the coast of Venezuela causes a tsunami that impacts both Venezuela and Puerto Rico, it is a local tsunami for Venezuela, but a regional tsunami for Puerto Rico.
  • If an earthquake off the coast of Alaska causes a tsunami that impacts both Alaska and Hawaii, it is a local tsunami for Alaska, but a distant tsunami for Hawaii.

Tsunami Characteristics

Not all tsunamis act the same. And, an individual tsunami may impact coasts differently. A small tsunami in one place may be very large a few miles away.

The speed of a tsunami depends on the depth of the ocean. In the deep ocean, tsunami waves are barely noticeable but can move as fast as a jet plane, over 500 mph. As the waves enter shallow water near land, they slow to approximately 20 or 30 mph. That is still faster than a person can run.

As the waves slow down, they can grow in height and currents intensify. Most tsunami waves are less than 10 feet high, but in extreme cases, can exceed 100 feet. When a tsunami comes ashore, it will not look like a normal wind wave. It may look like a fast-rising flood or a wall of water. Sometimes, before the water rushes on land, it will drain away suddenly, showing the ocean floor, reefs and fish like a very low tide. Tsunamis can travel up rivers and streams that lead to the ocean. A large tsunami can flood low-lying coastal areas more than a mile inland.

The series of waves that flood, drain away and then re-flood the land may last for hours or days. The time between waves ranges from five minutes to an hour. The first wave to reach the shore may not be the largest or the most damaging. It is not possible to predict how long a tsunami will last, how many waves there will be, or how much time there will be between waves.

Tsunami Dangers

A tsunami can be very dangerous to life and property on the coast. It can produce dangerously strong currents, rapidly flood the land and cause great destruction. The flow and force of the water and the debris it carries can destroy boats, vehicles, and buildings and other structures; cause injuries; and take lives as the tsunami moves across the land. It only takes six inches of fast-moving water to knock over an adult and two feet of fast-moving water to carry away most vehicles. The water can be just as dangerous (if not more so) as it returns to the sea, taking debris and people with it.

Even small tsunamis can be dangerous. Strong currents can injure and drown swimmers and damage and destroy boats in harbors. And, beware, a tsunami is not surf able. Tsunami waves are not like wind waves. They do not have a face, do not curl and break like wind waves and are full of dangerous debris.

 

Understanding Tsunami Alerts

There are four levels of tsunami alerts issued by the tsunami warning centers for United States and Canadian coastlines:

  • Tsunami Warning: Take Action—Danger! A tsunami that may cause widespread flooding is expected or occurring. Dangerous coastal flooding and powerful currents are possible and may continue for several hours or days after initial arrival.
    Follow instructions from local officials. Evacuation is recommended. Move to high ground or inland (away from the water). 
  • Tsunami Advisory: Take Action—A tsunami with potential for strong currents or waves dangerous to those in or very near the water is expected or occurring. There may be flooding of beach and harbor areas. Stay out of the water and away from beaches and waterways. Follow instructions from local officials.
  • Tsunami Watch: Be Aware—A distant earthquake has occurred. A tsunami is possible.
    Stay tuned for more information. Be prepared to take action if necessary.
  • Tsunami Information Statement: Relax—An earthquake has occurred, or a tsunami warning, advisory or watch has been issued for another part of the ocean. Most information statements indicate there is no threat of a destructive tsunami.

Note: Tsunami warnings, advisories and watches may be updated or cancelled as information becomes available. Advisories and watches may be upgraded if the threat is determined to be greater than originally thought.

Tsunami warnings are broadcast through local radio and television, wireless emergency alertsNOAA Weather Radio and NOAA websites (like Tsunami.gov). They may also come through outdoor sirens, local officials, text message alerts and telephone notifications.

There may not always be enough time for an official warning, so it is important that you understand natural warnings. If you are at the coast and feel a strong or long earthquake, see a sudden rise or fall of the ocean or hear a loud roar from the ocean, a tsunami may follow. This is your warning. Take action and move to a safe place. Do not wait for official instructions.

Tsunamis are among Earth's rarest hazards. But, even though tsunamis do not occur very often, and most are small and nondestructive, they pose a major threat to coastal communities, particularly in the Pacific. A tsunami can strike any ocean coast at any time. There is no season for tsunamis. We cannot predict where, when or how destructive the next tsunami will be. However, while tsunamis cannot be prevented, there are things you can do before, during and after a tsunami that could save your life and the lives of your family and friends. Read these pages to learn about tsunamis and what you can do to keep yourself and your loved ones safe in the event of a tsunami.

A tsunami is one the most powerful and destructive natural forces. It is a series of waves (not just one) caused by a large and sudden disturbance of the sea. Tsunami waves radiate outward in all directions from the disturbance and can move across entire ocean basins. Most tsunamis are caused by undersea earthquakes, but can also be caused by landslides, volcanic activity, certain weather-related phenomena and meteorites. Not all earthquakes cause tsunamis.

Tsunami Risk

Tsunamis are among the rarest of Earth's natural hazards. Each year, there are approximately two tsunamis that cause damage near their source. Destructive, ocean-wide tsunamis are more infrequent.

Tsunamis can strike any U.S. coastline, but the risk is greatest to coasts that border the Pacific. Low-lying coastal areas such as beaches, bays, lagoons, harbors and river mouths and areas along rivers and streams that lead to the ocean are at greatest risk. Tsunami waves can wrap around headlands, islands and sand spits, so coasts facing away from the tsunami source may also be at risk. Like earthquakes, tsunamis can happen at any time of the day or night, during any kind of weather and in all seasons.

Local, Regional and Distant Tsunamis

Tsunamis may be local, regional or distant. The type of tsunami depends on the location of the source of the tsunami and where it may strike land.

  • Local tsunami: The source of a local tsunami is close to the coast. It may reach the coast in less than one hour. There may not be time for an official tsunami warning, and you may only have a few minutes to get to safety. Since tsunamis are usually most dangerous near their source, it is important to recognize and respond to natural tsunami warnings, could be your only warning.
  • Regional tsunami: The source of a regional tsunami is generally between 60 and 600 miles away. Once generated, it takes a regional tsunami between one and three hours to reach the shore. There is time for NWS to issue an official tsunami warning. You should have a little more time to get to safety if told to do so. You may or may not feel the earthquake.
  • Distant tsunami: The source of a distant tsunami is far away, generally more than 600 miles away. Once generated, it takes a distant tsunami three or more hours to reach the shore. There is time for an official tsunami warning to be issued. You should have enough time to evacuate to a safe place if necessary.

What may be a local tsunami in one location may be a regional or distant tsunami in another. For example:

  • If an earthquake off the coast of Venezuela causes a tsunami that impacts both Venezuela and Puerto Rico, it is a local tsunami for Venezuela, but a regional tsunami for Puerto Rico.
  • If an earthquake off the coast of Alaska causes a tsunami that impacts both Alaska and Hawaii, it is a local tsunami for Alaska, but a distant tsunami for Hawaii.

Tsunami Characteristics

Not all tsunamis act the same. And, an individual tsunami may impact coasts differently. A small tsunami in one place may be very large a few miles away.

The speed of a tsunami depends on the depth of the ocean. In the deep ocean, tsunami waves are barely noticeable but can move as fast as a jet plane, over 500 mph. As the waves enter shallow water near land, they slow to approximately 20 or 30 mph. That is still faster than a person can run.

As the waves slow down, they can grow in height and currents intensify. Most tsunami waves are less than 10 feet high, but in extreme cases, can exceed 100 feet. When a tsunami comes ashore, it will not look like a normal wind wave. It may look like a fast-rising flood or a wall of water. Sometimes, before the water rushes on land, it will drain away suddenly, showing the ocean floor, reefs and fish like a very low tide. Tsunamis can travel up rivers and streams that lead to the ocean. A large tsunami can flood low-lying coastal areas more than a mile inland.

The series of waves that flood, drain away and then re-flood the land may last for hours or days. The time between waves ranges from five minutes to an hour. The first wave to reach the shore may not be the largest or the most damaging. It is not possible to predict how long a tsunami will last, how many waves there will be, or how much time there will be between waves.

Tsunami Dangers

A tsunami can be very dangerous to life and property on the coast. It can produce dangerously strong currents, rapidly flood the land and cause great destruction. The flow and force of the water and the debris it carries can destroy boats, vehicles, and buildings and other structures; cause injuries; and take lives as the tsunami moves across the land. It only takes six inches of fast-moving water to knock over an adult and two feet of fast-moving water to carry away most vehicles. The water can be just as dangerous (if not more so) as it returns to the sea, taking debris and people with it.

Even small tsunamis can be dangerous. Strong currents can injure and drown swimmers and damage and destroy boats in harbors. And, beware, a tsunami is not surf able. Tsunami waves are not like wind waves. They do not have a face, do not curl and break like wind waves and are full of dangerous debris.

 

Understanding Tsunami Alerts

There are four levels of tsunami alerts issued by the tsunami warning centers for United States and Canadian coastlines:

  • Tsunami Warning: Take Action—Danger! A tsunami that may cause widespread flooding is expected or occurring. Dangerous coastal flooding and powerful currents are possible and may continue for several hours or days after initial arrival.
    Follow instructions from local officials. Evacuation is recommended. Move to high ground or inland (away from the water). 
  • Tsunami Advisory: Take Action—A tsunami with potential for strong currents or waves dangerous to those in or very near the water is expected or occurring. There may be flooding of beach and harbor areas. Stay out of the water and away from beaches and waterways. Follow instructions from local officials.
  • Tsunami Watch: Be Aware—A distant earthquake has occurred. A tsunami is possible.
    Stay tuned for more information. Be prepared to take action if necessary.
  • Tsunami Information Statement: Relax—An earthquake has occurred, or a tsunami warning, advisory or watch has been issued for another part of the ocean. Most information statements indicate there is no threat of a destructive tsunami.

Note: Tsunami warnings, advisories and watches may be updated or cancelled as information becomes available. Advisories and watches may be upgraded if the threat is determined to be greater than originally thought.

Tsunami warnings are broadcast through local radio and television, wireless emergency alertsNOAA Weather Radio and NOAA websites (like Tsunami.gov). They may also come through outdoor sirens, local officials, text message alerts and telephone notifications.

There may not always be enough time for an official warning, so it is important that you understand natural warnings. If you are at the coast and feel a strong or long earthquake, see a sudden rise or fall of the ocean or hear a loud roar from the ocean, a tsunami may follow. This is your warning. Take action and move to a safe place. Do not wait for official instructions.

Before a tsunami

Before a tsunami

Even though tsunamis are rare, it is still important to prepare for one if you live, work or play on the coast. Many of the things you need to do to prepare for a tsunami are the same as those you need to do to prepare for the other hazards that may impact your community. But some actions are unique to tsunamis since response time may be limited. It is not hard, and it is not expensive. Here are some things you can do now to help protect yourself and your loved ones in case a tsunami ever strikes your community.

Know Your Risk

  • Find out if your home, school, workplace or other frequently visited places are in a tsunami hazard or evacuation zone and if your community has had tsunamis in the past. Your local emergency management office, your state's geologic or tsunami hazard website and your local National Weather Service Weather Forecast Office are good resources for information about your risk.
  • Find out if your community is TsunamiReady. Communities recognized by the National Weather Service as TsunamiReady are better prepared for tsunamis.

Understand the Warnings

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. Be prepared to respond immediately to whatever you hear or see first.

  • An official tsunami warning will be broadcast through local radio and television, wireless emergency alertsNOAA Weather Radio and NOAA websites (likeTsunami.gov). It may also come through outdoor sirens, local officials, text message alerts and telephone notifications.
  • There may not always be time to wait for an official tsunami warning. A natural tsunami warning may 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. Or, it could drain away suddenly, showing the ocean floor, reefs and fish like a very low tide. If you experience any of these warnings, even just one, a tsunami could be coming.

Practice All-Hazards Preparedness

  • Get a battery-operated NOAA Weather Radio to receive official alerts and other hazard information 24 hours a day, 7 days a week.
  • Sign up for email and text message alerts from your local emergency management office and make sure your mobile devices are set to receive wireless emergency alerts.
  • Make an emergency plan and a family communication plan and put together a portable disaster supplies kit that is easily accessible and contains basic items you and your family may need in any emergency. Include your pets in all your preparedness efforts. Since you do not know where you will be when disaster strikes, prepare kits for work and your car, too.
  • Meet with your family to discuss the plan and why you need to prepare for a disaster.
  • Practice your plan and keep it up to date.
  • Be a role model. Share your knowledge and plans with friends and neighbors so they can prepare themselves and their loved ones.

Plan for Evacuation

Your emergency plan should include evacuation plans.

  • Find out from your local emergency management office if there are evacuation routes and assembly areas identified for your community and if a map is available.
  • If assembly areas are not identified, plan to evacuate to a safe place that is on high ground or inland (away from the coast) and outside the tsunami hazard or evacuation zone. You may need to identify more than one safe place, depending on where you may be when you get a tsunami warning (e.g., home, work, etc.). You should plan to be able to reach your safe place on foot if you can because of possible road damage, closed roads and traffic jams. If you are concerned that you will not be able to reach a safe place in time, ask your local emergency management office about vertical evacuation. Some strong (e.g., reinforced concrete) and tall buildings may be able to provide protection if no other options are available.
  • Map out evacuation routes to your safe place(s) from your home, workplace or any other place you visit often that is in a tsunami hazard or evacuation zone.
  • Practice walking your evacuation routes, including at night and in bad weather. Familiarity with the routes will make evacuation quicker and easier if you ever need to evacuate for real.
  • If you have children that go to school in a tsunami hazard or evacuation zone, find out about the school's plans for evacuating and keeping the children safe. Find out where the assembly area is and where you should pick up your children after the danger has passed.
  • If you are a visiting an area at risk for a tsunami, find out about local tsunami safety. Your hotel or campground may be able to provide you with tsunami warning and evacuation information. It is important to know this information before a warning is issued. You may not have a lot of time after a warning. You do not want to waste it figuring out what to do.

Plan for Safe Boating

If you are on a boat and you get a tsunami warning, your response will depend on the size of the tsunami, the currents it produces, where you are, how much time you have before the first wave arrives and the weather at sea. If you are a boat owner or captain:

  • 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.
  • Find out how to respond to a tsunami warning and what to do if you are at sea when a damaging tsunami strikes your coast. Your harbor master, port captain, the U.S. Coast Guard and local and state emergency management offices are the best sources for tsunami safety information and regulations for boaters in your area.
  • 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.

During A Tsunami

During A Tsunami

During a tsunami, dangerous coastal flooding and powerful currents are possible and may continue for several hours or days after initial arrival. The first wave may not be the last or the largest.

Respond to a Tsunami Warning

How you respond to a tsunami warning depends on where you are and how you receive the warning. As described in Understand the Warnings, there are two types of tsunami warnings, official and natural. Both are equally important and suggest the potential for a tsunami that may cause widespread flooding. You may not get both types of warnings. Be prepared to respond to whatever you hear or see first. For your safety and others, always follow instructions from local officials.

If you are outside of the tsunami hazard or evacuation zone and you receive an official or natural tsunami warning, a tsunami is possible or likely, but you are in a safe place. Stay where you are unless local officials tell you otherwise.

Official Tsunami Warning

If you are anywhere in a tsunami hazard or evacuation zone or a low-lying coastal area and you receive an official tsunami warning, a tsunami is likely. The warning will estimate the tsunami's arrival time, describe potential impacts and recommend actions to take.

  • Stay out of the water and away from beaches and waterways.
  • Get more information about the threat and what to do from NOAA Weather Radio, local radio or television or your mobile device (text or data). Limit nonemergency phone calls to keep the lines open for emergency communications.
  • If local officials ask you to evacuate, implement your emergency plan and move quickly to your safe place outside the hazard or evacuation zone unless officials tell you to go somewhere else. 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.

Natural Tsunami Warning

If you are in a tsunami hazard or evacuation zone or a low-lying coastal area and you feel a strong or long earthquake, the ocean acts strange (e.g., it looks like a fast-rising flood or a wall of water or it drains away suddenly, showing the ocean floor like a very low tide) OR there is a loud roar coming from the ocean, a tsunami is possible and could arrive within minutes.

  • In case of an earthquake, protect yourself. Drop, cover and hold on. Be prepared for aftershocks, which happen frequently after earthquakes. Each time the earth shakes, drop, cover and hold on.
  • Do not wait for an official tsunami warning or for instructions from local officials.
  • As soon as you can move safely, implement your emergency plan and move quickly to your safe place outside the hazard or evacuation zone. If you do not have a safe place or cannot reach it, follow evacuation routes to safety or go as high or as far inland (away from the water) as possible.
  • When you are in a safe place, get more information about the threat and what to do from NOAA Weather Radio, local radio or television or your mobile device (text or data). Limit nonemergency phone calls to keep the lines open for emergency communications.
  • If there is earthquake damage, avoid fallen power lines and stay away from buildings, bridges and piers because heavy objects may fall from them during an aftershock.
  • Follow instructions from local officials. It is their job to keep you safe.
  • Stay out of the tsunami hazard or evacuation zone until local officials tell you it is safe. A tsunami may last for hours or days. The first wave may not be the last or the largest.

Note: If you are on the beach or near the water and feel an earthquake—no matter how big or how long it lasts—move quickly off the beach to high ground or inland (away from the water) as soon as you can do so safely. Get more information from the sources noted above.

Stay Safe

  • If there is earthquake damage, avoid fallen power lines and stay away from buildings, bridges and piers because heavy objects may fall from them during an aftershock.
  • Follow instructions from local officials. It is their job to keep you safe.
  • Stay out of the tsunami hazard or evacuation zone until local officials tell you it is safe. A tsunami may last for hours or days. The first wave may not be the last or the largest.

Stay Informed

Keep listening to NOAA Weather Radio or local radio or television or using your mobile device (text or data) to get the latest updates. Limit nonemergency phone calls to keep the lines open for emergency communications.

Observe Other Tsunami Alerts

During a tsunami advisory:

  • Stay out of the water and away from beaches and waterways. A tsunami with potential for strong currents or waves dangerous to people in or very near the water is expected or occurring.
  • Get updates about the tsunami from NOAA Weather Radio, local radio or television or your mobile device.
  • Follow instructions from local officials.

During a tsunami watch:

  • Get updates about the potential threat from NOAA Weather Radio, local radio or television or your mobile device.
  • Follow instructions from local officials.
  • Prepare to take action if necessary.

After a Tsunami

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 impacted areas.

Stay Safe

  • 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 been damaged by the tsunami 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.

Stay Informed

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 nonemergency phone calls to keep the lines open for emergency communications.

Contact Your Close Friends and Loved Ones

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