Edmonds tsunami warning siren gets first big test this week

Workers installed the Edmonds tsunami warning siren in June. While it has been regularly tested, Thursday’s Great Washington Shakeout will be its first time as part of a coordinated statewide drill. (Photo by Larry Vogel)

A new sound is coming to Edmonds, and you’ll get to hear it this Thursday, Oct. 21, at precisely 10:21 a.m.

No, the modulated wailing you’ll hear (click here to listen) is not a pre-Halloween arrival of ghouls, Valkyrie or banshees. It’s the first big test of the new tsunami warning siren installed on the Edmonds waterfront this summer at the foot of Dayton Street next to Olympic Beach Park.  Also called All Hazards Alert Broadcast (AHAB) sirens, the Edmonds siren is one of 121 installed or planned for our state. (See the accompanying map for locations of other Puget Sound area AHAB sirens)

This map shows locations of tsunami warning sirens in the Puget Sound area.

It’s all part of the Great Washington Shakeout, an annual event that not only tests warning systems, but helps raise awareness of the potential for natural disasters in our state, particularly earthquakes, and more importantly how to be ready when they strike.  Run by the Washington State Military Department, the Shakeout is held every year on the third Thursday of October. This year marks the tenth anniversary of the event.

A big part of the event is distributing information, raising awareness, and training citizens on how to prepare, what to expect in an earthquake, what to do when the earth starts shaking, and how to stay safe until the shaking stops. This information is summarized in the downloadable and printable Washington Shakeout Poster and in this video. Local groups, schools, churches, companies and individuals are urged to participate by registering and having their employees, friends and associates practice Drop, Cover, and Hold On. More information is in the Great Washington Shakeout FAQ here.

But back to tsunamis.

The purple line and blue shaded area show likely inundation in Edmonds in the event of a tsunami.

Despite being away from the ocean coast and mostly sheltered by the Olympic Peninsula, coastal areas in Puget Sound are in imminent danger of flooding in the event of a tsunami. For Edmonds, this means our waterfront beaches, parks, the railroad tracks, Harbor Square, Salish Crossing and more are at immediate risk of being hit and flooded by a tsunami wave (see inundation map above). It’s important to remember that this is not the kind of flooding we get from heavy rains that overcome stormwater systems and rise slowly. This is rapid, instant, one-minute-dry-and-the-next-under-rapidly-moving-deep-water events that literally knock you off your feet. It’s dangerous, and it can be deadly.

While earthquakes are difficult to predict and typically catch you by surprise, tsunamis generally give you time to prepare. This is because the epicenter of the earthquake that triggers a tsunami is usually far from coastal areas, and the tidal wave it generates moves from the quake epicenter through the water at a predictable pace.

The speed of a tsunami depends on the depth of the water it is traveling through. The deeper the water, the faster the tsunami. In the deep ocean, tsunamis can move as fast as a jet plane — over 500 mph — and can cross entire oceans in less than a day. As the waves enter shallow water near land, they slow to the speed of a car, approximately 20 or 30 mph. More information on tsunamis and their behavior is available on the NOAA/NWS FAQ here.

This map from NOAA shows the coastal areas in our section of Puget Sound that are at risk for inundation in a tsunami.

Depending on your distance from the epicenter, in almost all cases there’s enough time to evacuate low-lying coastal areas and head for high ground before the tsunami hits. This is where the tsunami warning siren comes in.

When NOAA and others who monitor earthquakes detect an event, they calculate how long it will take the tsunami to reach land and activate emergency warnings – like the Edmonds tsunami warning siren — for locations in its path.

You could be sitting on an Edmonds beach enjoying a sunny afternoon, deep into the latest Dan Brown thriller, when you hear the modulated siren followed by a message in English and Spanish to evacuate immediately to high ground. Don’t take time to fold up your chair and blanket – just go. Evacuation maps that include escape paths and even walk times to reach high ground have been made for many Washington communities likely to be hit hardest by tsunamis. None has yet been made for Edmonds, but new maps are being released all the time.

So listen up this Thursday morning! Because this is a drill and not an actual alert, the warning sound will be followed by a message in English and Spanish explaining that it is only a test.

Learn more on the Washington State Emergency Management Division’s tsunami website.

— By Larry Vogel

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