MENDOCINO Co, CA, 3/4/23 — Last week, the National Weather Service (NWS) heavily promoted a Wednesday morning tsunami test in California’s North Coast region across Mendocino, Humboldt, and Del Norte counties. The test allows NWS Eureka to run its Emergency Alerts system as it would in the event of a real tsunami, warning residents about the natural disaster using television chyrons, commercial and weather radio announcements, and sirens.
Shortly afterward, NWS Eureka asked North Coast residents on social media to share whether they’d received a tsunami warning. Some in Mendocino County reported hearing sirens but were unsure what it meant; some did receive the warnings; and some (like this reporter) chased an in-person tsunami alert around town to no avail.
We wanted to know how these tests work and what we should know about tsunami preparedness in Mendocino County, so we turned to the experts. Ryan Aylward, a meteorologist with NWS Eureka, talked with The Mendocino Voice about how this year’s emergency alerts improved upon prior tests, which areas of our coastline are most vulnerable, and what to do if you’re in the danger zone with a tsunami on the way.
How did the North Coast test go this year?
NWS Eureka tested its notification systems via sirens, television, radio, and NOAA weather radio last Wednesday from 11 a.m. to 12 p.m. Tests are “the only way to know the live code is going to show up on TV and look like the real thing,” Aylward explained.
While receiving qualitative data on social media is helpful, Aylward explained that NWS Eureka has no way to quantify how many people receive the test notifications year-to-year. But they do learn how well the tests are working and can spot if any piece of the puzzle needs extra attention.
“This year the big thing that we saw was that the audio came across much more clearly compared to previous years, and we think that was because we got a brand new microphone here at the weather office,” he explained. Some background noise on commercial radio, possibly caused by overlapping channels, will require further investigation.
NWS Eureka operates a texting system as well, which was not part of this test as it’s the same system used for earthquake warning alerts. Humboldt and Del Norte counties also tested their reverse calling system; essentially, a robocall residents can sign up for that alerts them to a possible tsunami based on their address. Mendocino County opted not to test this system this year, but residents who’d like to receive these calls in the event of an emergency can sign up via the Office of Emergency Services’ website. (The system accounts not just for tsunamis but for many types of disasters, such as wildfires or active shooters).
Should I have heard a siren in coastal Mendocino County?
Mendocino County has just four tsunami sirens along its coastline, with two in Noyo Harbor, one at Pudding Creek, and one in Point Arena Harbor. Aylward explained that on a still, clear day, these sirens can sometimes reach a 10-mile radius, but more typically can be heard within about one mile. This means that alerting unhoused community members or those who may not receive a text or hear a radio announcement falls to local jurisdictions.
“A lot of different systems will be activated in a real event, and sirens are just one of them,” he said. “They really have a limited range on how far they can reach, so you have to really effectively utilize them and position them in places where they’re going to reach the most people.”
This year, the siren at Pudding Creek didn’t go off and was not working as intended, Aylward said.
“If you were relying on that siren specifically, you’d have a problem,” he said. “So [you’d want to have] the weather radio, the reverse calling sign-up from the county — having those multiple ways to receive [an emergency alert] is really critical.
How dangerous would a tsunami be for Mendocino County residents?
Much of Mendocino County is actually less vulnerable to tsunamis than other parts of California, — towns on cliffs are at an advantage should large waves roll in following an earthquake.
“The vast majority of the coastline where people live is above the tsunami zone,” Aylward explained. “All of Fort Bragg, all of Mendocino, the town of Point Arena — it’s not an issue.”
He recommends that Mendocino County residents know the hazardous areas of the coastline — typically low-lying places like Noyo Harbor or Van Damme State Park — and avoid them should they receive an alert. These zones are marked off with blue signs along Highway 1, and the Redwood Coast Tsunami Work Group and California Geological Survey provide detailed tsunami hazard maps online.
These maps were updated only a few years ago, as the North Coast was the first region in California to take a more detailed look at its tsunami hazard zones via the aforementioned work group, Aylward said.
“It actually used to be that the zone didn’t cover the entire coastline,” he explained. “[It] used to just be the populated areas, so [the maps] left out a lot of areas on the Mendocino coast.”
The maps now span the entire coastline, and model worst case one-in-1,000-years disaster events that could spring from a variety of locations in the Pacific Ocean. The work group also reviewed these maps with the county’s emergency manager at the time, creating models of some geographical features and adding a high buffer for error.
“It came down to the modeling and then a good dive into every detail, looking at the high resolution terrain to make sure we’re determining the correct hazards based on the models,” Aylward said. “We took into account a 9.2 on the Cascadia and also in Alaska, so huge earthquakes, and then everything that was learned from the 2011 tsunami in Japan.”
If I’m warned of a tsunami while in a low-lying area, what should I do?
There are a couple types of tsunami alerts residents can receive, Aylward explained. One comes in the form of a localized earthquake: if you’re in the coastal zone and you feel an earthquake or are notified that one has happened close by, make sure you get to high ground quickly. If you receive an alert that an earthquake has occurred at a distance, in the middle of the ocean, you have a bit more time but should still leave the tsunami zone.
“If you’re going to recreate [there], or if you work in the tsunami zone, or if you happen to be one of the people that live in a tsunami zone, you … don’t want to be making that plan in the moment,” he said. “So when I go to the beach, I’m always looking around like, where would be the place that I would go if suddenly a big earthquake were to happen right now [and] I need to make it out of the zone in 10 minutes? I look around and come up with my plan.”
He added, “Especially if you live in the zone, you want to be thinking about, how am I going to catch the cat?”
He also emphasized that in the event of an earthquake, especially one that “lasts for a long time” people should be prepared to stay away from tsunami hazard zones for around 24 hours.
“Tsunami waves last for hours and hours and hours,” Aylward said. “It’s not a one-and-done event. It keeps going and the first wave is very rarely the biggest one.”
Note: Kate Fishman covers the environment & natural resources for The Mendocino Voice in partnership with a Report For America. Her position is funded by the Community Foundation of Mendocino, Report for America, & our readers. You can support Fishman’s work with a tax-deductible donation here or by emailing [email protected]. Contact her at KFishman@mendovoice.com or at (707) 234-7735. The Voice maintains editorial control and independence.