Blue and white warning signs going up on the Peninsula’s Pacific coast beaches infer a simple message:
In the event of a major earthquake or tsunami, turn around and run to high ground.
Massive waves known as tsunamis are a phenomenon most people — including Clallam County residents — associate with far-flung places, not with the ocean that reverberates just miles from their back yards.
“Tsunamis are a series of very long waves generated by any rapid, large-scale disturbance of the sea.
“Most are generated by sea floor displacements from large undersea earthquakes.”
So states a Clallam County Emergency Management Department information pamphlet.
So far, quakes in our region have been slow, devoid of the rapid motion that generates tsunamis.
‘Slow slip’
A recent long-term “slow slip” — a silent quake that Vancouver Island seismologists discovered on the deep part of the Cascadia subduction zone under the North Olympic Peninsula and slowly traveled north — raises the specter of a catastrophic quake and tsunamis on the Peninsula.
The slow slip, which ended more than a month ago, was so subtle that it went mostly undetected by Peninsula residents, though it had lingered for weeks.
Scientists call it an ETS, for “episodic tremor and slip.”
A silent ETS started July 8 beneath the North Olympic Peninsula — roughly under the western edge of the Dungeness Valley to the eastern shores of Clallam Bay and north-central Olympic National Park.
The Cascadia subduction zone, a 750-mile-long fault, extends offshore from northern Vancouver Island to Cape Mendocino, Calif.
The zone includes the Olympic Peninsula and Puget Sound areas to the Cascade Mountains.
Scientists now believe tension is building in the zone, which marks the boundary between the North America continental plate and the Juan de Fuca oceanic plate that dives beneath the North America plate.
That could cause the jolt that, in turn, stirs a tsunami on the coast and up the Strait of Juan de Fuca.
This is in great part why county emergency operations employees are conducting a special slate of meetings next week — to get the word out that tsunamis can occur along Clallam County’s many miles of coastline.
