ARI SHAPIRO, HOST:
Last week's earthquake off the coast of Humboldt County triggered a tsunami warning that urged people across a huge swath of California and part of Oregon to move to higher ground, regardless of how far above sea level they were. From member station KQED, Danielle Venton looks into why tsunami warnings still lack precision.
DANIELLE VENTON, BYLINE: First came the ShakeAlert from the U.S. Geological Survey. A large earthquake had been detected - drop, cover and hold on.
BILL CLERICO: And so our phones went off, you know, saying that there was an earthquake.
VENTON: Bill Clerico works in downtown San Francisco. Minutes later, he and 5 million others between Santa Cruz and Oregon received another alert, this one from the National Weather Service. It read in part, tsunami warning. You are in danger. Get away from coastal waters.
CLERICO: Being five blocks from the water here in San Francisco, that made me sit up straight in my chair.
VENTON: His wife works near the Waterfront as well, and his son goes to preschool nearby. The couple needed to decide if they should collect the family and get to higher ground. But the information he could find online - from cities, from counties, from the federal government, from schools - conflicted.
CLERICO: It was just generally quite confusing and concerning.
VENTON: He oscillated between thinking there was no problem and being really worried when...
CLERICO: Just as I was about to walk out the door, then the alert was canceled.
VENTON: For those who went to tsunami.gov, they saw huge sections of land - even miles inland and hundreds of feet above sea level - highlighted in red. Sites that listed tsunami hazard areas based on their topography were unavailable to some as worried people flooded the internet and media organizations scrambled to respond.
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UNIDENTIFIED REPORTER #1: And we do begin with breaking news because we have a 7.0 magnitude earthquake that has just hit northern California.
UNIDENTIFIED REPORTER #2: Now, this has actually triggered a tsunami warning.
UNIDENTIFIED REPORTER #3: You can see some of the cars there filling the local freeway and a lot of emergency responders as well.
VENTON: Some cities ordered evacuations. Schools called parents to pick up their kids. Transit agencies halted service. There were traffic jams. It was chaotic.
LORI DENGLER: One has to realize that we're still in the relative infancy, or maybe toddlerhood, of the tsunami warning world.
VENTON: Lori Dengler is professor emeritus at Cal Poly Humboldt. She's studied tsunamis for more than 40 years and is one of the scientists who advises the NOAA Tsunami Science and Warning program.
DENGLER: Part of the issue is that we don't put the resources into tsunami sciences like the Japanese do.
VENTON: Dengler also says we don't have as many offshore sensors or buoys. And another issue is with how these things are communicated.
DENGLER: In Japan, they have three levels of tsunami warnings. 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.
VENTON: The warning, triggered by provisional data gathered quickly, is based on the worst-case scenario - a massive 9.0 earthquake in the Pacific Northwest. But even in a worst-case scenario, more people would get the warning than would need to evacuate to safety. That's because the region's tsunami warning areas are borrowed from official weather forecast areas. They might share the same weather but not necessarily the same flood risk. That means people who need tsunami warnings get them, as well as a lot of people who don't, says Dengler. And then the public has to wait for officials to refine or cancel the warning. She feels this one took a long time to cancel.
DENGLER: We ended up being in a tsunami warning, I think most of us would agree, for a longer period than we were comfortable with.
VENTON: What would be great is something that could alert only those in tsunami hazard zones, says Dave Snider from NOAA's National Tsunami Warning Center in Alaska. They send out alerts for the whole country.
DAVE SNIDER: If we had something like that, it would change the game. We've been working on that for a long time.
VENTON: But NOAA doesn't have that technology yet. And, he says, officials need to be cautious and give warnings early as possible. A significant tsunami could have reached the Humboldt and Mendocino coasts in minutes. Largely, he thinks the alert was successful.
SNIDER: The most important part about what happened on Thursday is that the public responded in the way that we need them to respond.
VENTON: NOAA's tsunami advisory committee will be meeting this month and will discuss whether criteria for issuing alerts should be modified and if alerts could be more granular. To prepare for the next tsunami, you can check ahead of time if you're in a risky area at tsunamizone.org.
For NPR News, I'm Danielle Venton in San Francisco. Transcript provided by NPR, Copyright NPR.
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