Santa Rosa’s earthquake gave the Bay Area its first real test of the nation’s new ShakeAlert system, and it was a qualified success, warning thousands of residents on Tuesday night with a loud alarm and instructions to seek cover.
“The moment the wave hit the house, my watch and phone went off. It’s a miraculous technology — a definite win,” said Robert Stephens, who was sitting at a table at his home on Sonoma Mountain, about five miles from the quake’s epicenter.
In downtown Sonoma, the alarm sent journalist Sarah Stierch diving under her dining room table for protection. “Very impressed with the alert — it’s my first experience with it,” she wrote on Twitter.
But many residents at greatest risk did not receive an alert until after the shaking started because they were so close to the epicenter. The system gives longer warnings to those who are farther away from the rupture.
After more than a decade in development, the ShakeAlert system is finally a reality for over 50 million West Coast residents. Created by the U.S. Geological Survey, it is 81% complete, with more than 903 buried sensors in California that can mobilize cellphone users who are at risk. When complete, it will have 1,115 sensors and quicker transmission time.
“The good news is that we’re going in the right direction,” said USGS’s Robert de Groot, the national coordinator of outreach and education for ShakeAlert.
“The ShakeAlert system behaved as we expected it would last night,” he said, “and it shows that we’re continuing to improve earthquake early warning on the West Coast.”
The system initially overestimated the earthquake’s magnitude, calling it a 4.9; later, the quake was downgraded to a magnitude 4.4. But it identified the site of the quake’s rupture with extreme accuracy, pinpointing the epicenter 2.4 miles north of Santa Rosa.
In some spots, it was overenthusiastic, puncturing the serenity of a seismically uneventful evening. “The alert scared me to death,” wrote Anna Boucher, of San Rafael, who said she did not experience any shaking.
In other places, it worked just as planned. At a youth soccer game in Rohnert Park, “everyone’s phones went off with emergency alerts — and then we felt the quake about 20 seconds later,” tweeted Matthew Valkovic. “It was pretty wild!”
Sometimes it came too late. By the time Santa Rosa resident Kathy McMorrow got the alarm, she and her dog had already felt the temblor and were down the porch stairs. Spectators at the town’s Montgomery High School basketball game heard the alert after the main shock but before the aftershock.
Alexa Chipman heard the clamor after the earth finally stood still. “I was like ‘so helpful…I noticed, thanks!’” she joked on Twitter.
While there were few reports of damage or injury, the city has dispatched public works employees to assess possible damage to essential services and city infrastructure.
ShakeAlert’s performance has been a disappointment in some previous earthquakes, especially in rural regions where there are few sensors. While fast, it wasn’t accurate.
But Santa Rosa’s 4.4-magnitude shaker and a 4.3-magnitude aftershock — which struck about two miles northeast of downtown, causing some bottles and other items to topple off store shelves — triggered a near-perfect alert for residents of densely populated communities in Sonoma County, as well as some adjacent towns in Napa, Marin, Contra Costa, Alameda and Mendocino counties, even San Francisco’s Presidio.
At least 20,000 people got the apps’ messages, with more getting notice from FEMA and Google, said de Groot.
USGS has prioritized high-population areas, especially those located near major faults, in its ‘build up’ strategy. Businesses and public agencies such as BART are already acting on alerts from the system.
Communities on the distant edge of Tuesday’s “shake zone” received an alarm well in advance, up 30 seconds before the shaking.
ShakeAlert relies on cell phones — so residents who weren’t near their phones, or who hadn’t downloaded the app, missed the message.
For the system to send an alert, the earthquake must be recorded as having a magnitude of 4.5 or more. Although the final magnitude was lower, the quake initially registered at 4.9.
Shake Alert does not predict earthquakes, but it detects an earthquake’s initial waves. These waves, which travel quickly, are weaker than the more damaging second set of waves.
When the system’s sensors detect these first waves, it enlists high-speed telemetry to send that ground motion information to processing centers in Seattle, Menlo Park and Pasadena. Within about five seconds, computer algorithms analyze the data to rapidly identify the epicenter and strength of the earthquake and publish a data package, called a ShakeAlert message.
The ShakeAlert message is picked up by government and private partners. FEMA may issue a Wireless Emergency Alert, like an AMBER Alert.
An alert may also be issued by two different apps: the MyShake app, developed by the UC Berkeley, or the QuakeAlertUSA app, a product of Early Warning Labs. Alerts are also delivered though cell phones using Google’s Android Operating System.
The alert buzzes loudly and warns users, with text: “Drop, cover and hold on!”
It was a much more effective message than what was issued during Santa Rosa’s catastrophic 2017 wildfires, said Stephens, the founder of Best Buy’s Geek Squad.
When alarms sounded during those fires, residents “were walking in circles and did not know what to do, did not know what to pack,” he recalled. “People can’t think during the moment that they’re in crisis.”
“It was very reassuring to be told, ‘This is what’s happening. This is what you do,’ ” he said.
“And the speed at which it came through,” he said, “gives me great confidence in the whole sensor array that they’ve set up.”
How to get a USGS ShakeAlert message:
• Wireless Emergency Alerts, such as an AMBER Alert, are delivered by FEMA’s Integrated Public Alert and Warning System. It is not necessary to sign up for alerts but make sure you didn’t turn off the option. For questions, contact your cell phone service provider.
• The MyShake app is available for free in the Apple iTunes and Google Play stores. Learn more: https://myshake.berkeley.edu/
• The QuakeAlertUSA app is available for free on the Apple iTunes and Google Play stores. Learn more: https://earlywarninglabs.com/mobile-app/.
• Google provides a ShakeAlert-powered earthquake alert feature that is integrated into the Android Operating System. Go to Safety and emergency option in Settings on your phone and select “Earthquake alerts.”