New tsunami simulations paint dire picture for WA coast

SEATTLE - The Washington State Department of Natural Resources is renewing its warning that devastation could hit our coastlines and flow inland should the "big one" hit.

New tsunami wave simulations show the impacts of a Cascadia Subduction Zone magnitude 9.0 earthquake and the resulting tsunami that will follow.

"The warm colors in the simulation, the deep waves are high tsunami waves of 10 feet or greater," explains Corina Allen, Chief Hazards Geologist with the state's Department of Natural Resources.

The Cascadia Subduction Zone quakes every 300-600 years and it's been 320 years since the last "big one" which means we are due for another earthquake.

"There is no earthquake season. It could happen today, it could happen tomorrow or 50 years from now," said Allen.

The new simulations paint a dire picture for Washington's coastal communities. In the event of a large Cascadia Subduction Zone event, as soon as the quake starts, the ground ruptures and generates a tsunami wave.

The wave can hit the outer coast in 15 to 20 minutes. Geologists produced localized simulations for 8 coastal communities and says Grays Harbor and Willapa Bays will be the hardest hit with significant inundations in low lying coastal communities.

"We recommend people plan their evacuation routes and know where high ground is and how to get there, but also if you don't have a vertical evacuation structure, some of the only options is getting to a roof or tallest structure nearby and hoping that building can survive the earthquake and tsunami," said Allen.

Allen said tsunami waves can continue hitting the coast for multiple hours and even an entire day in some cases and spread inland. That's why it's not safe to leave your safe place after the first wave.

"You'll see continuous wave action along the outer coast and then you can see the wavefront propagate down the Strait of Juan De Fuca and it splits at around Port Townsend and heads north into Bellingham and the San Juan Islands and then it heads south down the Hood Canal into Seattle, Tacoma and down into Olympia," warns Allen.

Wave arrival time after the quake for Seattle is 2 hours and 20 minutes. It can reach Tacoma in 2 hours and 40 minutes, and in Olympia in 4 hours after the quake. The quake itself can also cause extensive damage to buildings, powerlines, and bridges.

The drive home message is to prepare: have a way to get alerts and if you feel the earth-shaking, drop, cover and hold on.