Tsunami


What is a tsunami?

The Pacific Coast, Strait of Juan de Fuca, Puget Sound, and large lakes are at risk from tsunamis, which are a series of extremely long waves that threaten people and property along shorelines. Sudden raising or lowering of the earth’s crust during earthquakes are usually the main cause of a tsunami, although landslides and underwater volcanic eruptions also can generate them. Movements of the sea floor or lakebed, or rock fall into an enclosed body of water, displace the water column, setting off a series of waves that radiate outward like pond ripples.

In the deep ocean, tsunami waves are relatively harmless. Only as a tsunami approaches land does it become a hazard; in shallow water, it gains height as its waves slow and compress. Tsunamis do not resemble their usual icon, a towering wave with a breaking crest. Instead, they come onshore resembling a series of quickly rising tides, and they withdraw with currents much like those of a river. Swift currents commonly cause most of the damage from tsunamis. A Pacific Ocean tsunami can affect the entire Pacific basin, while a tsunami in inland waters can affect many miles of shoreline.

Tsunamis typically cause the most severe damage and casualties near their source. There, waves are highest because they have not yet lost much energy. The nearby coastal population often has little time to react before the tsunami arrives. Persons caught in the path of a tsunami often have little chance to survive - debris may crush them or they may drown. Children and the elderly are particularly at risk, as they have less mobility, strength and endurance.

Check out mil.wa.gov/preparedness to learn about how you can prepare yourself and loved ones for all of Washington’s hazards, including tsunamis.

Tsunami Evacuation and Inundation Maps

Partnering with local communities, Washington’s Emergency Management Division (WA EMD) and the Department of Natural Resources (WA DNR) develop maps based on tsunami modeling data. These maps include Pedestrian Evacuation Walk Time maps, Tsunami Inundation maps, and Tsunami Current Velocity maps. You can find these maps, along with additional area-specific information, at our Tsunami Resources page.

Tsunami Alerts

The U.S. National Weather Service (NWS) operates two Tsunami Warning Centers which are staffed 24 hours a day, 7 days a week. The main mission of the warning centers is to help protect life and property from tsunamis. The National Tsunami Warning Center (NTWC) in Palmer, Alaska is responsible for monitoring and alerting the coastlines of Alaska, Canada, the continental United States, Puerto Rico, and the Virgin Islands. To do this they monitor observational networks, analyze earthquakes, evaluate water-level information, issue tsunami alerts, conduct public outreach, and coordinate with government, academic, and international organizations.

Tsunami messages are issued by the Tsunami Warning Centers to notify emergency managers and other local officials, the public, and other partners about the potential for a tsunami following a possible tsunami-generating event. Initial tsunami messages include alert level(s), preliminary information about the earthquake, and an evaluation of the threat. If a tsunami is already suspected, the message may also include wave arrival times, recommended life safety actions, and potential impacts. Subsequent messages, both updates and cancellations, are based on additional seismic analysis and results from the tsunami forecast models and may feature more refined, detailed, and targeted information.

For the United States, Canada, and the British Virgin Islands, these messages include alert levels. There are four levels of tsunami alerts: warning, advisory, watch, and information statement.

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  • 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, but there is no threat or it was very far away and the threat has not been determined. In most cases, there is no threat of a destructive tsunami.

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

Official tsunami warnings are broadcast through local radio and television, marine radio, Wireless Emergency Alerts (WEA), NOAA Weather Radio and NOAA websites like Tsunami.gov. They may also come through outdoor sirens, local officials, text message alerts and telephone notifications.


Natural warning signs: 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 you…

  • 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 very soon. This is your warning! Take action immediately and move to a safe place (to high ground or inland) immediately. Do not wait to receive an official alert or instructions.


Receiving Tsunami Alerts

The U.S. National Tsunami Warning Center issues tsunami information for the continental U.S. and Canada. They have a Twitter account where they post official notices at https://twitter.com/NWS_NTWC. To receive notifications when a tweet from @NWS_NTWC is sent, you must choose to be notified within the Twitter app on your mobile device and/or through the twitter.com website. For instructions on how to set up tweet notifications (also known as “push” notifications) to your device, check out this help menu.

The Northwest Association of Networked Ocean Observing Systems provides the NVS Tsunami Evacuation App, available to download for free in the Apple App Store and on Google Play. The NVS Tsunami Evacuation App provides an at-a-glance view of where the tsunami hazard zones are along the Oregon and Washington coast, and allows you to map whether your home, work, school, etc. is located in a tsunami evacuation zone or not. To help you develop and plan your own evacuation routes, the Tsunami Evacuation App enables you to save your current position or points of interest via GPS or address look-up. It also pushes tsunami alert notifications directly to your phone.

NOAA Weather Radio All Hazards (NWR) is a nationwide network of radio stations broadcasting continuous weather information directly from the nearest National Weather Service office. NWR is an "All Hazards" radio network, making it your single source for comprehensive weather and emergency information. In conjunction with Federal, State, and Local Emergency Managers and other public officials, NWR also broadcasts warning and post-event information for all types of hazards – including tsunamis. To learn more about purchasing a NOAA Weather Radio receiver, check out the National Weather Service here.

Do you have a Reecom weather radio model 1630? This is the model WA EMD and many local jurisdictions utilize and distribute to the public. If so, we have created a video to help you program your radio. Check it out!

The United States’ National Weather Service provides InteractiveNWS (iNWS), an application suite able to send NWS products to local partners in multiple ways, including as emails and texts. Visit https://inws.ncep.noaa.gov/ to learn more or to sign up for the service. Once your registration has been accepted you can go onto the site and set up text alerts by county/parish, lat/long, or street address. You can also draw a polygon on the map provided to set up a custom alerting area.



Be sure to also check out www.mil.wa.gov/alerts and sign up for your local alerts system, as tsunami warnings may come through these avenues also. In addition, you can follow WA EMD, WA DNR, and NWS Seattle and Portland* on social media at the links below to ensure you get updated and accurate event information as quickly as possible. Because we never know when or where disaster will strike, it’s important to have multiple ways of receiving alerts.

*NWS Seattle is responsible for all inner coast Washington counties, as well as Clallam, Jefferson and Grays Harbor counties. NWS Portland is responsible for Pacific County.

Tsunami Sirens

The Washington Emergency Management Division maintains a network of 122 state-of-the-art All-Hazard Alert Broadcast (AHAB) tsunami sirens (PDF) in high-risk locations throughout the inner and outer coasts. These sirens are intended to act as an OUTDOOR alerting method for people and communities on/near the beach who may not otherwise have access to other official alerting methods. They have an audible range of approximately 1 mile, though this varies depending on environmental factors like topography, wind direction, and physical barriers (trees, buildings, etc). The sirens are not intended to be heard indoors. This outer coast siren map shows the locations of AHAB tsunami sirens located on Washington’s outer coast and this inner coast siren map shows the locations of AHAB tsunami sirens located on the inner coast.

Upon the issuance of a TSUNAMI WARNING, the sirens play a wail sound (click here to listen to what it sounds like) followed by a voice message in English and Spanish instructing listeners to evacuate immediately to high ground.

During a routine TEST of the AHAB tsunami siren system, which is conducted on the first Monday of every month at noon, the sirens play the Westminster Chimes (click here to listen to what it sounds like). The sirens are also tested once a year with the actual wail sound on the third Thursday in October in conjunction with the Great Washington ShakeOut. For this yearly test, the wail sound is followed by a voice message in English and Spanish explaining that it is only a test.

Tsunami Resources and Education Materials

Maritime Guidance

Tsunamis are a risk for all of the coastal communities in Washington state, yet nowhere is this risk more evident than at port and marina facilities located along the shoreline. These facilities are central to the maritime community and are an integral part of the Washington economy. As part of its work to help mitigate tsunami risk to the maritime community, Washington Emergency Management Division is excited to announce the completion of Washington State’s first Tsunami Maritime Response and Mitigation Strategy for the Port of Bellingham. This strategy was built upon established maritime guidance from the National Tsunami Hazard and Mitigation Program that has been used to create maritime strategies in California, Oregon, and Alaska. WA EMD has expanded these existing strategies to create a maritime strategy that is not only tailored to the Washington coast’s unique tsunami threat, but also includes detailed, actionable recommendations for both tsunami response and mitigation and site-specific tsunami mapping. The strategy was designed to be used as a template for other Washington maritime communities to develop strategies to help improve their tsunami response and mitigate tsunami risk. We hope this strategy will help the maritime communities in Washington more fully understand the tsunami risk they face and assist them in their tsunami planning efforts in the future.

Port of Bellingham

Public Education Materials

Tsunami Vertical Evacuation

Coastal communities that lack sufficient natural or artificial high ground are particularly vulnerable to tsunamis because residents, employees and visitors will have limited time to evacuate to safety. For Washington’s at-risk outer coast communities, tsunami vertical evacuation structures (VES) are a vital way to save lives. Evacuation structures are designed to withstand an earthquake, aftershocks, liquefaction and multiple tsunami waves. They can be included as part of a new building or be a standalone tower. Evacuation structures have performed successfully in Japan and have also been built in New Zealand.

Ocosta Elementary School near Westport, Washington, was completed in 2016 and is the first tsunami VES in North America. Washington’s second VES in Tokeland, WA is currently under construction thanks to the Shoalwater Bay Tribe.

Tsunami vertical evacuation structures are unique and complex. Planning, modeling, designing and constructing these structures is different from your typical building project. Strong community involvement and leadership are needed to evaluate the need for evacuation structures, plan for potential locations, locate funding and follow through to the end of construction and beyond. Partnerships with local, state and federal agencies, universities and various experts are also key to success. In Washington, planning, funding and design work for additional structures are currently underway. These exciting efforts provide inspiration for communities along the Washington coastline and for coastal communities elsewhere in the United States and around the world.

2021 Outer Coast Tsunami Vertical Evacuation Assessment

The Washington Emergency Management Division recently had an assessment done on tsunami vertical evacuation structure needs for Pacific, Grays Harbor and Clallam counties. This assessment, conducted by the Institute for Hazards Mitigation Planning and Research at the University of Washington, analyzed potential sites for vertical evacuation structures using walk-time estimates based on a tsunami from a 9.0 magnitude earthquake along the Cascadia Subduction Zone. The research team used their findings to develop four vertical evacuation options for each community studied. These options range from no vertical evacuation structures to the highest number needed to attain total coverage.

The study is accompanied by maps showing proposed tsunami refuge locations, photos of the locations, the number of people within 15-25 minutes’ walk to high ground and graphics displaying the data in an easily readable format. Summary tables for each county identify the minimum number of structures needed for the entire county and the percent/number of people in the tsunami zone who would be within 15- or 25-minutes’ walking distance of high ground if all those structures were built.

Now that this assessment has been completed, Washington has a much more accurate idea of how much artificial high ground it will take to ensure the most vulnerable communities on the outer coast can quickly evacuate in the event of a Cascadia tsunami. Local jurisdictions can use these findings when they apply through WA EMD for grant funding through FEMA’s Building Resilient Infrastructure and Communities (BRIC) hazard mitigation grant program. Projects that design or construct tsunami evacuation structures have a good chance of being funded if their plan is realistic and feasible. If you’re interested in learning more about potential funding opportunities for your community, check out mil.wa.gov/hazard-mitigation-grants or email HMA@mil.wa.gov.

Compressed PDFs for each study county are available for download below:

Vertical Evacuation Structure Planning Resources

We are constantly working with local governments and tribes on grants for tsunami vertical evacuation structures. We can help you, too! Download our Tsunami Vertical Evacuation Manual to learn more about the process:

Our team also hosted a workshop that talked about tsunami vertical evacuation structures in Ocean Shores. Watch the presentation here, courtesy of TVW.

Project Safe Haven

Project Safe Haven is a grassroots, community-driven public process currently taking place on the Washington Coast to identify areas for future vertical evacuation structures. Partnering with local residents, its mission is to develop a community responsive vertical evacuation strategy along the Washington coast.


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