SEATTLE — Washington’s coastlines experienced only minor surges Saturday from a tsunami triggered by a spectacular underwater eruption in the South Pacific.
Waves of 1 foot or less were measured at sites from Westport and Neah Bay on the outer coast, to Port Angeles on the Strait of Juan de Fuca. Neah Bay, at the state’s most northwestern corner, registered a 1.1-foot surge.
The impacts were more dramatic in a few places along the West Coast, especially Santa Cruz, Calif., where rushing water swamped boats in the harbor and flooded the surrounding area. Waves exceeded 4 feet at Port San Luis, south of Monterey. In some parts of Alaska’s Aleutian Islands the tsunami reached 3.3 feet.
Shortly after the early morning eruption off the coast of the Pacific nation of Tonga, the National Tsunami Warning Center issued a tsunami advisory for the entire U.S. West Coast, warning that waves of 1 to 3 feet would sweep northward for several hours.
The advisory for the Washington and Oregon coasts was canceled shortly before 5 p.m.
Some of the first waves to hit the Washington coast surged ashore on the Long Beach Peninsula at about 8:30 a.m., but Scott McDougall, emergency-management director for Pacific County, described them as “subtle.”
“To the best of my knowledge, we had no damage whatsoever,” he said late Saturday afternoon.
In a Facebook post, an observer at nearby Cape Disappointment State Park described rapidly breaking waves that were larger than usual. “The water seemed unsettled and almost jiggly.”
Sandra Hollenbeck, who has a home near the jetty in Ocean Shores, said the waves were a bit more fierce than usual — especially for a windless day. “It was definitely some pretty big, breaking waves,” but never posed a threat to roads or homes.
King County’s Emergency Management Department issued an alert warning residents to avoid beaches and waterfront areas because of the possibility of strong waves and currents. But impacts in Puget Sound proved to be minimal.
The event marked the first Pacific-wide tsunami warning from a volcanic eruption instead of an earthquake, said Harold Tobin, director of the Pacific Northwest Seismic Network at the University of Washington. In fact, the only other volcanic outburst to trigger such wide-ranging tsunamis was the 1883 eruption on the Indonesian island of Krakatau, he said.
And the submarine Tongan volcano that exploded Saturday may not be done, Tobin cautioned. “There’s a possibility it could have another bigger, small or similar-sized eruption in the coming days, weeks, months or years.”
Despite the unusual nature of the event, the tsunami-warning system worked well, Tobin added. The advisory was issued quickly and communicated widely.
At least some local alert systems also met the test. Pacific County sent out 17,000 reverse 911 messages via text, email and phones, to residents living closest to the shore, McDougall said. The messages explained that the impacts would be limited to the immediate beach area and advised people not to evacuate.
Many residents posting on the Eye of the Storm Pacific County Facebook page said the text and phone messages came through quickly, though others said they received no notification or experienced glitches.
While Washington was unscathed this time, the tsunami advisory is a reminder of the region’s vulnerable position and geologically volatile nature. “Events like this (advisory) really help us wake up and consider the possibility of a more locally generated earthquake event — the big one,” Tobin said.
An earthquake on the offshore Cascadia Subduction Zone could trigger massive tsunamis that crash into the coast within 10 to 15 minutes after the ground stops shaking.
People in areas with no high ground, like parts of the Long Beach Peninsula and Ocean Shores, would be hard-pressed to evacuate in time. A recent analysis by Washington’s Emergency Management Division estimates the state needs to build at least 58 vertical evacuation structures — either towers, berms or tsunami-resistant buildings — to ensure coastal residents can escape the high water.
At least 36 state school buildings are also in tsunami zones.
