U.S. West Coast remains ill-prepared for tsunami, says science report

More than six years after the Indian Ocean tsunami shocked the world with its deadly power, communities along the West Coast of the United States remain ill-prepared for a similar event, concludes a report from the National Academy of Sciences.

An earthquake on the offshore fault called the Cascadia subduction zone could send waves crashing to the shores of Washington, Oregon and Northern California within minutes — not enough time for local authorities to issue warnings or evacuate, said review leader John Orcutt, of the Scripps Institution of Oceanography.

"That's what happened to Banda Aceh (in Indonesia), and the disquieting thing is that it could happen to us," he said.

The only way to prepare people for such a fast-moving disaster is to deeply ingrain a simple message, Orcutt said: When the ground shakes or the water pulls back from the shore, move uphill as quickly as possible.

States and local communities have undertaken education programs to spread that message, but results are uneven and approaches vary widely. In some towns, local residents removed tsunami-evacuation signs because they didn't want to scare off tourists, Orcutt said. The quality of offshore mapping and computer models to predict how far the water will reach also differs across states.

The report recommends a more uniform approach in terms of signs, warning messages, educational approaches and risk assessment.

"You need good coordination to deal with tsunamis," added Oregon State University civil-engineering professor Harry Yeh, who served on the review committee. "These kind of events are not local business — they're everybody's business."

The analysis was requested by Congress, which boosted funding for ocean buoys and tidal gauges after the 2004 Indian Ocean tsunami. Today, a network of 39 buoys stretches from Alaska to South America, capable of detecting tsunami waves as they pass.

The high-tech instruments are mainly useful for tsunamis generated by distant earthquakes — off the coast of South America, for example. In that case, several hours of warning time would allow for the evacuation of coastal communities, Orcutt said.

But nearly a third of the buoys are out of service at any time because of malfunctions, Orcutt said. "That's a very, very large number." The report recommends the National Oceanic and Atmospheric Administration (NOAA), which runs the buoy network, beef up maintenance or design hardier instruments.

Once the buoys and gauges detect a tsunami, there needs to be a "flawless" system for alerting residents and evacuating vulnerable communities — but that doesn't exist in many places, Orcutt said.

The committee called on NOAA's Tsunami Warning Centers in Hawaii and Alaska to better coordinate their efforts. The centers issue initial warnings based on earthquake signals. Each center uses different computer systems and different software, so they're not able to back each other up, Orcutt said.

After an offshore earthquake in 2005, the centers issued conflicting and confusing warnings that led to evacuations in some West Coast communities and complacency in others.

Tsunami awareness has increased tremendously since the Indian Ocean disaster, Yeh, the OSU profession said. But with federal funding already dropping, it's not clear how long that awareness will last.

"Tsunamis are rare events," Yeh said. "What's going to happen 20 years from now? One hundred years from now?"

The last major earthquake and tsunami from the Cascadia fault occurred 300 years ago.

Japanese communities help keep tsunami awareness high by building memorials to earlier disasters, Yeh said.

The Oregon town of Cannon Beach is considering construction of an earthquake- and tsunami-resistant building that could serve both as a city hall and a refuge. On Washington's Long Beach Peninsula, where there's very little high ground, leaders are mulling the idea of building berms where people could gather to escape a tsunami surge, Yeh said.

Sandi Doughton: 206-464-2491 or sdoughton@seattletimes.com