What to Do When You Receive a Tsunami Alert
1) Know what the alert means
2) Find yourself on the Oahu Tsunami Evacuation Map
3) Stay alert and informed
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. Since 1946, more than 220 people have died in Hawaii, including six on Oahu, due to tsunamis. 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.
View our multilingual tsunami resources.
Understanding Tsunami Alerts
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. Review the DEM Understanding Tsunami Alerts and know what each alert means to you and your family and what actions to take. You can also click on the image for a downloadable PDF version.
When You Need to Evacuate
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. 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. The Oahu Tsunami Evacuation Map illustrates two Tsunami Evacuation Zones:
How long do I have to evacuate?
Local Tsunami
If a tsunami is generated locally, you only have minutes to react. Local tsunamis originate from nearby sources, with waves arriving in as little as 30 minutes on Oahu. An earthquake on or near Hawaii Island is the most likely cause of a local tsunami on Oahu. Because there is minimal time to react and alert the public about a local tsunami, it is essential to understand the natural warning signs of a tsunami.
Distant Tsunami
Tsunamis generated far away from the coast of Hawaii are considered distant tsunamis. The following are the estimated times that waves will reach Hawaii for tsunamis generated in various locations worldwide.
Tsuami Warning and Evacuation; where do we go?
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 an Evacuation Zone
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.
School Evacuation
Make sure you know your child's school tsunami evacuation plan. In Hawai'i, public schools within tsunami evacuation zones conduct evacuation drills to train staff and students to quickly and safely evacuate. For more information on Hawaii Public School emergency plans, visit the Hawaii State Department of Education site.
Natural Tsunami Warning Signs
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.
What happens after a tsunami?
A tsunami may be destructive or non-destructive. If the tsunami were destructive, emergency search and rescue operations would immediately start on land and at sea. It is essential to wait for official messaging that an area is safe and re-entry is allowed. Following a tsunami or a Tsunami Warning, here are some things to be aware of:
- Tsunami waves may keep coming for hours, every 10 minutes to one hour apart. The first wave may not be the largest.
- 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.
- It's essential to stay informed. Check local radio/TV stations, HNL.info, or NOAA Weather Radio for emergency information regarding safety and disaster assistance.
More About Tsunami Threats
- 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.
- Tsunami events have no season like hurricanes. A tsunami can occur at any time of the day or night, at any time of the year.
- Shallow, undersea earthquakes, underwater volcanic eruptions, landslides, slumps, and meteorites usually cause tsunamis.
- Homes and small buildings are not designed to withstand tsunami impacts. It is imperative to evacuate immediately when a Tsunami Warning is issued.
- Learn more about tsunamis from the NOAA National Weather Service tsunami education and outreach website www.weather.gov/safety/tsunami-outreach
Tsunami Information, Education, and History Resources
NOAA Pacific Tsunami Warning Center (PTWC)
The NOAA Pacific Tsunami Warning Center (PTWC) is DEMs primary source of information whenever an earthquake occurs in the Pacific basin that could generate a destructive tsunami affecting the State of Hawaiʻi. PTWC's information guides us in making critical evacuation and population protection decisions.
To provide notifications as early as possible, PTWC uses preset criteria based on preliminary earthquake information before a tsunami is detected to help them decide when and for where to issue tsunami messages and what alert(s) to include. Subsequent messages and alerts are based on impact estimation resulting from additional seismic analysis, water-level measurements, tsunami forecast model results, and historical tsunami information.
Get real-time information from the PTWC and the NOAA US Tsunami Warning System here at https://tsunami.gov/
NOAA International Tsunami Information Center (ITIC)
Located on Ford Island in the NOAA Daniel K. Inouye Regional Center, the International Tsunami Information Center (ITIC) monitors international tsunami warning activities in the Pacific and other oceans to recommend improvements in information dissemination systems. ITIC is also a clearinghouse for developing educational and preparedness materials to support government and non-government organizations, schools, and the general public efforts in tsunami preparedness and awareness. Many of their resources are available online here www.tsunamiwave.info
Tsunami History
Knowing your tsunami history is essential to understanding the hazards these events create and the areas on our islands that tsunamis have impacted.
In Hawaiʻi, your best source for tsunami history is the Pacific Tsunami Museum (PTM) in downtown Hilo. Co-founded in 1988 by Dr. Walter Dudley and Jeanne Branch Johnston, the museum's mission and goals are to promote public tsunami education for the people of Hawai'i and visitors worldwide, preserve the social and cultural history of Hawai'i, and serve as a living memorial to those who lost their lives in past tsunami events.
The next time you visit Hilo, visit the Pacific Tsunami Museum. Learn more at their website http://tsunami.org/
DEM  | City and County of Honolulu | HI-EMA | American Red Cross of Hawaii |