Outdoor tsunami warning sirens arrive in North Sound – Everett Post


A new outdoor tsunami warning siren system was recently installed on the Edmonds waterfront just off Dayton Avenue. The siren system is properly known as the All Hazards Alert Broadcast or AHAB, and joins the more than 70 that are found along the Washington coast, in the Strait of Juan de Fuca, and in Whatcom County. .

The Washington Legislature recently approved $ 2.7 million to be added to $ 150,000 in NOAA federal funds to add more AHABs which, when completed, will involve 122 outdoor siren systems.

The new Edmonds system can be found at the front of the new AHAB assembly being installed. In the North Sound, two more will be installed along the Everett waterfront, eleven in Skagit County and six in Island County. Others include five more in Whatcom County as well as additional AHABs along the coast and across the Strait to help fill in the gaps. The new Everett systems will soon be installed at the Port of Everett at 2900 Terminal Avenue and near the 10 Street boat launch.

The greatest tsunami threat in the Northern Strait comes from the Cascadia Subduction Zone, about 100 nautical miles off the Pacific Northwest and Vancouver Island. The last Cascadia earthquake occurred in January 1700 and scientists found it to occur roughly every 300 to 500 years, which means we are in the time window.

North Sound AHABs would provide a delay of approximately one hour before the arrival of the first tsunami wave carried by Cascadia. These tsunami waves shouldn’t be big angry Hollywood waves in the North Sound, but rather a flood of low lying areas. The Cascadia earthquake and tsunami would likely be similar to the Japanese event of March 2011 – the two to five minutes of tremors will be easily felt, and by far the biggest damage from the tsunami would be along the outer coast .

Yet there are significant seismic faults that cross Puget Sound. They include the Tacoma Fault, the Seattle Fault and, more importantly, the North Sound Fault, the South Whidbey Island Fault. Geological evidence shows that these seismic faults produced a local tsunami.

In the case of these local seismic faults, the shaking itself serves as a warning. Once the shaking has stopped, move to higher ground, away from the shores of Puget Sound. Snohomish County emergency authorities conducted an exercise in fall 2019 to better prepare for a South Whidbey Island fault event that involved a predicted magnitude 7 earthquake.

These AHAB outdoor siren systems will play both a loud siren as well as a verbal message indicating what the warning is and what to do. They also have a US Coast Guard light at the top of each AHAB to assist the hearing impaired. The AHAB system is also regularly tested to ensure that it remains fully operational. On the first Monday of each month at noon, the AHAB emits a Westminster chime.

These AHABs are exterior systems. Inside, residents, businesses, schools and other facilities should use a NOAA All Hazards Weather Radio (NWR) to receive not only tsunami warning messages, but also a variety of weather and other broadcast warning messages. by local emergency authorities as a key part of the Emergency Alert System (EAS). For more information on NOAA Weather Radio, visit the NWR website hosted by the National Weather Service. A NOAA weather radio receiver is a lifeline for the cost of a pair of shoes.

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