DNR Prepares Tsunami Hazard Maps Of Guemes Island

Tsunami Hazard Maps

This modeling indicates the first tsunami waves will reach the Anacortes/Bellingham areas about 1.5 hours after the Cascadia earthquake, with inundation depths as high as 18 feet and current velocities in excess of 20 knots.

The Washington State Department of Natural Resources (DNR) published new maps showing the likely impacts to communities on the north Salish Sea mainland from a tsunami generated by a magnitude 9 earthquake on the Cascadia subduction zone.
 
These new maps are prepared by the Washington Geological Survey, a division of DNR, and are intended to help local officials prepare evacuation and recovery plans.
 
“Earthquakes and tsunamis are very real threats that we must be proactive in preparing for,” said Commissioner of Public Lands Hilary Franz. “That’s why DNR’s team of highly-trained geologists works each day to ensure our communities have the information they need to prepare and be safe.”
 
The new modeling uses a simulated magnitude 9 earthquake on the Cascadia subduction zone – an event that geologic history shows occurring approximately every 2,500 years. This modeling follows building code standards for critical facilities, and assumes greater inundation than previous modeling so communities can plan for worst outcomes.
 
Tsunami inundation is expected to continue for more than 8 hours.

Current Speed
The modeled current speed is shown in four ranges: 0–3 knots, 3–6 knots, 6–9 knots, and >9 knots... These ranges approximate hazards to ships and docking facilities, representing no expected damage, minor/moderate damage possible, major damage possible, and extreme damage possible, respectively. Modeled current speed locally exceeds 20 knots in the study area and is strongest in narrower waterway channels and nearshore where the tsunami–tide interactions are likely to be most significant. Key areas of strong currents are Guemes Channel, Burrows Pass, Clark Point, and Eliza Rock.

Model Results From A ~2,500-Year Cascadia Subduction Zone Earthquake Scenario:

This new study and maps are posted online at: http://www.dnr.wa.gov/publications/ger_ms2018-02_tsunami_hazard_anacortes_bellingham.zip


The Cascadia Earthquake and Tsunami
The Earthquake That Will Devastate the Pacific Northwest. When the Cascadia fault line ruptures, it could be North America’s worst natural disaster in recorded history.