How Confusion Over California's Tsunami Warning Shows the Limits of US Forecasting

After Thursday’s blaring tsunami alert sent out a wave of confusion across Northern California, authorities are using it as a lesson in preparing for future disasters.

But one expert in Humboldt said the day reveals just how much the country has to learn about forecasting tsunamis, calling it “deja vu all over again.”

According to Lori Dengler, an emeritus professor of geology at Cal Poly Humboldt, not much has changed about the U.S.’s tsunami warning system since a similar near-coast earthquake hit in 2005.

“The entire West Coast from San Diego up to the Canadian border was put into a tsunami warning and a tsunami did not materialize,” she said. “[The U.S.] is still in the relative infancy or maybe toddlerhood of the tsunami warning world in terms of having the kinds of instrumentation offshore, having the kinds of models to forecast [their] impacts.”

It wasn’t until the 1990s that many people realized that tsunamis don’t only come to the West Coast from far away, she said. They can actually originate as close as the Cascadia Subduction Zone, a fault that spans a long stretch about 100 miles offshore.

The U.S. officially began tsunami forecasting in 1949 and has opened two Tsunami Warning Centers in Alaska and Hawaii since. The centers’ notifications have three levels of ascending seriousness: watch, advisory, and what was issued Thursday: warning.

Dengler said there are a lot of shades of grey under that “warning” umbrella.

“In Japan, they have three levels of tsunami warnings,” she told KQED. “They have a small tsunami, a medium tsunami and a big tsunami. In the U.S., we just have one level. We just have ‘warning.’”

An earthquake that meets a prespecified set of standards based on magnitude, location and depth triggers a warning, no matter how close, or far, from the cut-off it is.

The map of at-risk zones and guidance for a local response, when there’s a warning issued, is based on a model researchers designed for a worst-case earthquake event on that underwater Cascadia fault — “the big one” — Dengler said.

Map by Matthew Green/KQED

The tsunami hazard area (shaded orange) represents the “maximum considered tsunami runup from several extreme, infrequent, and realistic tsunami sources,” according to the California Department of Conservation, which provided the geographic data for this map.

“We don’t have a ‘little’ tsunami evacuation zone,” Dengler said. “We can’t tell people, ‘This is only a tsunami ‘C,’ not a tsunami ‘B’ or ‘A,’ and so these are the only areas that are at risk because we don’t have the basic science or the instrumentation to be able to do that level of detail yet.”

That’s why Thursday’s tsunami warning — which many people have been tempted to deem an overreaction — was so far-reaching, and confusing for even city governments trying to decide how to keep their populations safe.

Berkeley probably took the warning most seriously, implementing an evacuation order for West Berkeley’s evacuation zone within about a half hour. Fourth Street businesses closed, Interstate 80’s onramp at University Avenue shut down and at least one day care asked parents to pick up their kids before the warning was called off less than an hour later.

Officials there say the decision was based on state guidance after the city received the blanket “warning” Dengler referenced.

“The message indicated that a ‘Warning-level’ tsunami of at least 3 feet would hit the shores of San Francisco by 12:10pm, implying that Berkeley would likely be hit shortly thereafter,” spokesperson Matthai Chakko wrote via email. “Pre-existing state guidance indicated that such a tsunami could reach as far east as portions of 7th Street” and “prompted the City to issue an evacuation order for the affected area.”

Other disruptions rippled throughout the bay: BART temporarily shut down service in its Transbay Tube, Salesforce Tower began an evacuation, and San Francisco warned coastal residents to move at least a block inland and avoid evacuation zones.

After the immediate threat had passed, San Francisco fire rescue captain Justin Schorr warned residents not to write off the day as a false alarm.

“If we weren’t prepared today to evacuate inland or to higher ground, this gives us a great opportunity to be prepared for next time,” he told KQED.

So how prepared is the Bay Area, and wider West Coast?

Delger said that refining the national Tsunami Warning System would require investment in offshore instruments and more personnel.

“There’s no way right now to pull the San Francisco Bay’s communities — Alameda, the Marin County part that’s on the bay — there’s no way to pull those communities out of the warning,” she told KQED. “The system is not set up now to do localized threats within Puget Sound, within San Francisco Bay, or really parsing the details of any of the coasts.”

Local cities also have kinks to work out.

Hours after its evacuation was called off, Berkeley sent out a survey requesting feedback about how it handled the morning.

In nearby Alameda, resident David Howard said he didn’t receive any of the city’s text messages until after the warning had passed, though it says it sent out multiple through its alert system. Traffic was also backed up at Posey Tube, the westernmost exit off the island.

In the event of a tsunami that does materialize, Howard worries the city isn’t prepared to safely evacuate everyone who could be in a risk zone.

“It’s about how do we evacuate people off the island? I don’t have faith in my government that we have a good plan,” he said.

A comment from the city of Alameda was not available by the time this story was published.

In San Francisco, there was a noticeable lack of blaring emergency sirens, which residents got used to hearing at lunchtime on Tuesdays before they were taken out of commission in 2019 for repairs. The system was expected to return to service after two years, but it remains offline.

Mary Ellen Carroll, the executive director of the San Francisco Department of Emergency Management, said that after initial assessments, the total cost to refurbish the system ballooned from about $2 million to over $20 million, and currently, the city has no money budgeted for these repairs.

She also said that the most effective channels of communication have evolved since the system was built in the 1940s.

“The Wireless Emergency Alert [WEA] yesterday is the way that we do alerting in this country for major events,” she told KQED. “The main thing is that it gave you information, whereas a siren does not. A siren just goes off, and then you have to figure out why is the siren going off. A WEA, a text alert, a phone call — those are ways that are much more effective.”

Dengler warned, though, that in the event of a really “big one,” these methods of communication might not be ironclad.

“When we have a magnitude 9 earthquake on the Cascadia Subduction Zone, people aren’t going to get an alert because our infrastructure is likely to be damaged,” she said. “They have to know on their own what to do and where to go.”

Still, Carroll said repairing the existing Outdoor Public Warning System isn’t a top priority. The DEM has been looking into other ways to provide the same value — reaching people without phones when cell service or power is out — with newer technology that sends more targeted messages.

This upgrade, and many others being discussed to prepare the Bay Area for “the big one” will require more investment than seems to be coming from the local or federal level.

“If we want a better tsunami warning system, we have to put resources into allowing our warning system to give us more quality, localized information,” Dengler said. “If we had done that, we probably would have seen a very different story in terms of the tsunami warning area for this particular event.”