What is a Tsunami?
Tsunamis are a series of hazardous, large, long ocean waves caused by earthquakes or volcanic eruptions under the sea. You cannot swim or surf tsunamis because they flood the land like a rushing river (or fast-rising tide) rather than curling and breaking like a regular surfing wave. A tsunami picks up and carries debris, significantly increasing the chance of injury, property destruction, and death. Tsunami waves may keep coming for hours, every 10 minutes to one hour apart. The first wave may not be the largest.
Tsunamis strike with devastating force and quickly flood all low-lying coastal areas, threatening life and property. Tsunamis travel as fast as a jet airliner (approximately 500 mph) in the deep ocean with waves only a few inches high. As they approach the shore, they slow down but increase dramatically in height. Historically, locations in Hawaii have been flooded with water more than 30 feet deep. Since 1946, more than 220 people have died in Hawaii, including six on Oahu, due to tsunamis.
Tsunamis can occur at any time so knowing if you’re in an evacuation zone, recognizing the natural warning signs, and understanding how you will be alerted can make the difference between life and death.
There are two different types of tsunamis that could impact Hawaii. Learn more about each one by hovering over the boxes below:
Local Tsunami
Local Tsunami
Distant Tsunami
Distant Tsunami
Tsunami alerts are issued in Hawai’i by the Pacific Tsunami Warning Center (PTWC). There are four levels of tsunami alerts: warning, advisory, watch, and information statement. Each alert type is tied to a specific action for you to take. When an alert is issued, stay tuned to local radio/TV stations and official social media for more detailed or specific information.
Am I at risk where I live?
When there is a Tsunami Warning, the public will be advised which evacuation zone to leave. Don’t wait to evacuate. It can take time to clear an evacuation zone, so go as quickly and safely as possible. Homes and small buildings are not designed to withstand tsunami impacts. It is imperative to evacuate immediately when a Tsunami Warning is issued.
Use the Oahu Tsunami Evacuation Map to know if you are in a Tsunami Evacuation Zone (TEZ) or an Extreme Tsunami Evacuation Zone (XTEZ). If the map is slow or not responding, you can use the National Oceanic and Atmospheric Administration’s version of the map.
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- Tsunami Evacuation Zone (TEZ): TEZ is used for most tsunami warnings. This zone is based on the historical tsunami impacts on the State of Hawaii and the Island of Oahu over the past 100 years. These areas are shown in RED on the map. For this evacuation, you are considered safe when you have reached the YELLOW or GREEN Zones.
- Extreme Tsunami Evacuation Zone (XTEZ): If an earthquake happens in the Eastern Aleutian Islands with a magnitude 9.0 or greater, it will cause a rare, more extreme tsunami event that would result in much more extensive flooding throughout Oahu. In this rare case, officials may advise evacuating further inland beyond the TEZ. These areas are shown in YELLOW on the map. For this evacuation, you are considered safe when you have reached the GREEN Zone.
There are two different kinds along O’ahu’s roadways and in parks. The signs in this graphic were installed at extreme tsunami zone (XTEZ) entrances and exits, in coastal parks, and along major roadways around O’ahu to help residents and visitors “Know Your Zones”.
For the vast majority of tsunami warnings, only the standard tsunami zone will need to be evacuated. For those evacuations, you do not need to exit the extreme zone (pasted the signs). Tsunami Hazard Area signs serve both as marker for the extreme zone boundary and as a reminder of the tsunami hazard. Scan the QR code on the park signs to quickly find out the boundary of the tsunami zone.
Signs in Coastal Parks:
Signs along Roadways:
When a Tsunami Warning is issued, leave the evacuation zone as soon as possible. Anywhere outside the evacuation zone is considered a safe place. If possible, make plans to evacuate to a family member or friend’s home who lives outside the evacuation zone. During a Tsunami Warning, car traffic may be heavy and can cause delays, so plan to walk to a safe location if possible.
Immediately evacuating when the Warning is issued is critical for geographically isolated coastal communities requiring extended travel time to leave evacuation zones.
Vertical Evacuation If you are near the shore and cannot quickly walk or drive out of an evacuation zone, Vertical Evacuation is an option that could save your life. To vertically evacuate, proceed to the fourth floor or higher of a building that is 10 stories or taller.
Tsunami Evacuation Sites Public facilities with restrooms and parking may be made available if time permits. These will be announced on local television, radio, and official social media channels. These are not shelters and will not have other services. Shelters will only open, if needed, following a destructive tsunami wave arrival.
If you are not in a tsunami evacuation zone and a Tsunami Warning is issued, stay home and stay off the road. We want to keep roads and highways open for evacuees leaving the coastline and provide emergency access to first responders assisting with the evacuation.
How do I stay safe?
There are a few things you need to do in order to be prepared for and stay safe in the event of a tsunami warning. Take whatever actions you can now to be ready if there is a tsunami coming.
Before a Tsunami is Coming
Taking action today, before a tsunami is threatening our island, will help ensure you have all the plans and supplies you need. Don’t wait to prepare until a tsunami is coming because you will not have much time.
Every family is unique and so is every family’s emergency plan. Think about what special people, pets, or circumstances you should plan for. Do you have keiki or kupuna who might need extra help in an emergency? Do you have a pet that you need to pack food or a crate for? What about your power requirements? Do you need electricity for medical devices? Identify the needs and make a plan for each member of the family ahead of time so you can be confident you can take care of your family in an emergency.
Every emergency plan should include some essential things:
- Know if you will have to evacuate your home.
- A location where your family plans to meet if you need to evacuate or are separated.
- Contact information for family members, friends, workplaces, medical providers, and other important contacts. Establish an off-island or out-of-state contact that everyone in your family knows to contact in the event on-island communications are limited.
Learn more at honolulu.gov/dem/preparedness/make-plan.
Given the limited warning time for a local tsunami, natural warning signs may be your first alert that something is wrong. If you observe warning signs, don’t wait for guidance. Take action immediately. Suppose you are in a tsunami hazard, evacuation zone, or low-lying coastal area and feel an earthquake. In that case, the ocean acts strange, or a roar is coming from the sea, so a tsunami is possible and could arrive within minutes. Water movement may look like a fast-rising flood or a wall of water or drain away suddenly, showing the ocean floor like a shallow tide. If you observe these natural warning signs, evacuate the beach and move to higher ground immediately. Do not wait for official guidance. This could generate or be a sign of a local tsunami with minimal warning time.
Some disasters or emergencies like tsunamis require quick evacuation. This can occur with little warning, and there may not be enough time to take your entire family disaster supply kit with you.
A Go Bag should provide enough quick-access supplies to get you through the initial phases of an emergency and evacuation. You should have one bag for each member of your household.
Find out what to include in your Evacuation Go Bag at honolulu.gov/dem/build-a-kit.
Living on an island means that it is extremely important to have a 14-day disaster supply kit. Unlike areas in the continental US, Hawaiʻi residents don’t have the option to drive somewhere that hasn’t been impacted when a hurricane happens. We must be ready with food, water, and emergency supplies in case goods cannot be offloaded from ships, transportation on island is not available, or utilities are out.
Your 14-day disaster supply kit should include everything your household would need to survive for two weeks without utilities or access to outside supplies.
Find out what to include in your 14-day kit at honolulu.gov/dem/build-a-kit.
Check out the “Am I at Risk Where I Live” section of this page to find out if your home is in the a tsunami evacuation zone.
Check your insurance policies to determine what, if any, tsunami-related damage is covered by your policy. Standard homeowner and renters’ insurance do not include certain disaster hazard coverage.
When a Tsunami is a Threat
Once we know a tsunami is predicted to impact Hawaii, it is time to begin preparing your home and family for potential impacts.
When a Tsunami Warning is issued, leave the evacuation zone as soon as possible. Anywhere outside the evacuation zone is considered a safe place. If possible, make plans to evacuate to a family member or friend’s home who lives outside the evacuation zone. During a Tsunami Warning, car traffic may be heavy and can cause delays, so plan to walk to a safe location if possible.
Immediately evacuating when the Warning is issued is critical for geographically isolated coastal communities requiring extended travel time to leave evacuation zones.
Check the contents of your evacuation go bag to ensure you have everything you need.
- If you live outside the tsunami evacuation zone, stay off the roads unless there is a critical need. This will help reduce traffic and help ensure those who must evacuate have the ability to do so.
- Monitor local radio stations for emergency information and important updates.
After a Tsunami
After a tsunami is over, make sure you are staying safe while you assess damage or begin clean up efforts.
Continuously monitor TV and radio for instructions. Authorities will announce when it is safe to go outside and/or to return to your home.
A cancellation is different than an all-clear message. A cancellation is issued only after an evaluation of water-level data confirms that a destructive tsunami will not impact an area under a warning, advisory, or watch or that a tsunami has diminished to a level where additional damage is not expected.
Coastal tsunami impact areas could be flooded, debris from structures may block roads and highways, and major utilities disrupted for days to weeks or longer. Be aware that you may be unable to return to coastal areas for hours or days. The public cannot re-enter these areas until it is safe.
Following a Tsunami Warning or Tsunami Advisory, it may be unsafe to return to the beach for hours or even days.
Be aware of hazards, i.e. down power lines, broken gas lines, contaminated water, weakened structures, broken glass, etc. Debris on roadways will limit your ability to drive around.
When assessing damage, take photos to document your losses.
Once it is safe to return and you have photographed damage, begin cleaning immediately to avoid further hazards like mold growth.