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.
The 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.
- 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 National Tsunami Warning Center has 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.
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.
The National Weather Service also 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, latitude/longitude, 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.
- WA EMD Facebook and Twitter
- WA DNR Facebook and Twitter
- NWS Seattle Facebook and Twitter
- NWS Portland Facebook and Twitter
*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.
WA EMD maintains a network of 121 state-of-the-art All-Hazard Alert Broadcast (AHAB) tsunami sirens 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 map shows the locations for tsunami sirens as of Oct. 15, 2020.
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
- WA DNR Tsunami Evacuation Maps
- The Great Washington ShakeOut
- National Weather Service Tsunami resources
- WA DNR interactive geology portal
- WA DNR geologic hazard maps
- Materials to Download
- Tsunami Basics (English, PDF)
- Tsunami Basics (Spanish, PDF)
- 2013 WA State Hazard Profile: Tsunami (PDF)
- Tsunami All-Hazard Alert Broadcast brochure (PDF)
- Tsunami All-Hazard Alert Broadcast Siren brochure (PDF)
- Tsunami Trivia (PDF)
- Disaster Response Guidebook - For Hotels and Motels on Washington's Coast (PDF)
- Surviving a Tsunami - Lessons from Chile, Hawaii, and Japan (USGS)
- Sobreviviendo a un Tsunami (USGS)
- Tsunami webinar slides
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 at-risk communities, tsunami vertical evacuation structures (VES) are a 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 or berm. 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. 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 State, 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.
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.
- Clallam County
- Grays Harbor County
- Pacific County
- Four Select Vertical Evacuation Site Estimated Costs - Appendix C (PDF)
- Tsunami Vertical Evacuation On The Washington Coast (PDF)
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