WASHINGTON — On the heels of a rare tsunami advisory for Washington’s coast, following a major volcanic eruption in Tonga last weekend, the state Department of Natural Resources has released maps and findings from a new study examining how severe — and how quickly — tsunami impacts affect the Olympic Peninsula in the wake of a major Cascadia earthquake.
The state released more than a dozen new tsunami maps to accompany its detailing of the study’s findings earlier this week. Those findings projected tsunami behavior after the “The Big One,” a magnitude 9.0 earthquake along the Cascadia subduction zone, which experts say could happen within in the next 50 years.
Should that happen, the tsunami impacts would be swift.
Researchers estimate the resulting tsunami would move quickly along the coast and the Strait of Juan de Fuca, with the first waves arriving in La Push within 10 minutes, followed by Moclips, Copalis Beach and Neah Bay in 20 minutes, Clallam Bay in 30 minutes and Port Angeles within an hour.
Researchers explain in the study’s abstract:
“The first modeled rising tsunami wave arrives at La Push within 10 minutes from the start of the earthquake shaking. However, localized flooding due to subsidence could occur within minutes of the earthquake. The crest of the first modeled tsunami wave exceeds 30 ft (9 m) and reaches many locations along the Pacific coast within ~30 minutes. Flooding depths on land also reach or exceed 60 ft (18 m) along most Pacific coastline beaches and campgrounds. The first modeled rising wave of the tsunami also travels into the Strait of Juan de Fuca and reaches Port Angeles in ~1 hour with a wave amplitude of ~20 ft (6 m). There is limited time to issue official tsunami warnings and any felt earthquake shaking should act as an immediate warning. Fast-moving currents from the tsunami waves locally exceed 9 knots off Washington’s Pacific coastline and within some areas in the Strait of Juan de Fuca, presenting a significant navigational hazard to the maritime community.”
The study projects flood depths would reach or surpass 60 feet along most coastal beaches, with inundation as high as 100 feet at Yellow Banks Beach. Researchers estimate inundation from tsunami waves would continue for about eight hours, and present hazards to mariners for at least 24 hours.
State officials said the study was designed to help inform and improve Washington’s tsunami response plans and help low-lying, coastal communities prepare for a significant natural disaster.
Source: Bellevue Patch