Tsunamis and the Cascadia Subduction Zone

The Cascadia Subduction Zone (CSZ) is a 1,000 kilometer fault where the Juan de Fuca and North American plates meet. Located off the Pacific Northwest coast, this plate runs from central Vancouver Island, B.C. to northern California. The CSZ has a history of producing large earthquakes and will produce 8.5M earthquakes or larger in the future. Aside from the ground shaking, liquefaction, and aftershocks that would result from an earthquake of this magnitude, coastal lands are threatened by the tsunami that may follow. 

Tsunami wave height and extent of inundation will vary depending on a complex set of factors. However, one of the most important factors is the distance between land and the epicenter of the earthquake. With Bellingham being tucked into the Puget Sound, it is expected than a tsunami caused by a CSZ earthquake would take just over 2 hours to reach the shore. Although there is little to no warning before an earthquake occurs, there are multiple types of warning systems for tsunamis and it is essential to identify and use as many as are available to you.

There are both natural and technological warning systems for tsunamis. One of the first and most important warning signs is a large earthquake. If the ground shakes for an extended period of time or it is difficult to remain standing, it is likely a tsunami will follow. If you are on or near the coast you should evacuate inland or to high ground immediately. Bellingham currently has one tsunami siren located in Squalicum Harbor, however it is not guaranteed you will hear this siren go off. Therefore, it is important you know the natural warning signs so you can evacuate in time.

Bellingham had tsunami inundation and evacuation maps updated with the latest modeling in 2019. These maps should guide your evacuation plan. However, it is important you practice your evacuation plan and be aware of alternative routes as the earthquake may damage bridges or roads, ultimately blocking your path. If you live or work in the inundation zone, talk to your employer about evacuation plans and resources.

 

Frequently Asked Questions

What is a tsunami?

A tsunami is a series of waves most commonly caused by an earthquake beneath the sea floor. As tsunamis enter shallow waters, such as Bellingham Bay, they increase in height causing potential for great loss of life and property damage as they reach the shore. Research suggests tsunamis have struck the Washington coast on a regular basis. Tsunamis can happen regardless of time of day, weather conditions, or time of year.

How will Bellingham be impacted?

There is no definite answer to this question. Impacts will depend on other conditions such as tides, wave height/depth, and number of waves. The best things you can do to prepare are to know the possible evacuation routes and be prepared to leave the inundation zone for an extended period of time. If you permanently reside in the inundation zone, you should establish a plan with family members or friends that live nearby outside of the inundation zone.

Where should I evacuate?

If a tsunami is imminent, you should evacuate inland or to high ground immediately. If a tsunami has been caused by a local earthquake, it is likely that roads will be damaged and cell phone signal will be lost. Therefore it is important you establish a meeting place with your family, household, or close neighbors in the event of an evacuation.

If you feel the ground shake, evacuate inland or to high ground immediately! Although walk times are indicated on the map, they may vary depending on road or weather conditions. Know your abilities, as well as alternative routes not indicated on the map, for an earthquake can damage infrastructure such as bridges and roads.

What do I do after evacuating?

Once you have evacuated the inundation zone, you should not return until an official all clear has been issued. Tsunami waves can last for hours and will likely cause extensive damage in the inundation zone posing risk to life and safety. Once an all clear has been issued, the area may be restricted to authorized personnel. Therefore, it is important to have a plan beforehand and evacuate with any critical supplies, documentation, or proof of ownership.

Where can I find more information?

For more information please visit:

WA Department of Natural Resources Tsunami Page

Bellingham Tsunami Evacuation Walk Times (PDF)‚Äč

Bellingham Tsunami Evacuation Map-North (PDF)

Bellingham Tsunami Evacuation Map-South (PDF)


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