After 4.6 Earthquake Jolts Santa Cruz, Seismologists Double Down on MyShake Alerts

A blaring alarm woke Cian Dawson early Thursday morning. It was the MyShake phone app, alerting him to a 5.1 magnitude earthquake about to rock the region.

Dawson stayed in bed, thinking he wouldn’t have enough time to get under a table.

A few seconds later, the Berkeley resident’s room began to shake. “It made more sense to me to stay where I was,” Dawson told KQED.

The tremor near Boulder Creek prompted the MyShake phone app and local agencies to alert hundreds of thousands of residents across the greater Bay Area and Central Coast. The USGS later downgraded the quake to a 4.6. More than 10,000 people reported the quake in the app, saying they felt light to moderate shaking, and there were two reports of destroyed buildings.

In light of the relatively moderate-sized quake and a false alarm issued by the app last year, some Bay Area residents have questioned whether agencies issue too many warnings and whether these alerts really make us safer. But seismologists argue they are important for protecting the public in the long run.

Dawson said there needs to be more outreach about how seriously to take the messaging, because people are beginning to train themselves to ignore the alerts.

“The ‘boy who cries wolf’ is a great way to describe people’s response when they don’t understand what the alert actually means,” Dawson said.

Angie Lux, a scientist specializing in earthquake early warnings at the UC Berkeley Seismological Laboratory, said she thought the alert worked well, as it reached its ultimate goal of protecting lives and reducing injuries. Lux said that the farther someone is from the earthquake’s source, the longer it will take to receive a warning.

“For the people that are right next to the epicenter, they’re not going to receive much warning,” Lux said.

Evan Hirakawa lives in Scott’s Valley, just a few miles away from the source of Thursday’s quake. The USGS research geophysicist said he felt the quake first, then his phone pinged.

“It was pretty intense at my house,” Hirakawa said. “The shake alert kind of worked, but it was too close for it to really benefit me.”

Hirakawa said there’s evidence that indicates the earthquake likely took place on a fault that hasn’t ruptured in a long time — the Zayante Fault in Santa Cruz County, which sits roughly between two major fault systems: the San Andreas and the San Gregorio.

“We have [Zayante] labeled in our databases as maybe it’s inactive now,” Hirakawa said. “It was active thousands of years ago, but we haven’t seen a lot of historical earthquakes on it.”

While this shaking may seem like an outlier, Hirakawa said he doesn’t think Thursday’s quake “is a foreshock to something bigger.” But, he said, it’s still worth paying attention to early warning messages, because doing so might just be “life-saving.”

“The fact that so many people who felt the earthquake got the alert this morning is a good sign that the early warning stuff is at least working,” Hirakwa said. “It will be unfortunate when it happens, but the system will only be tested when there’s a large, destructive earthquake. That’s when it’s going to matter.”

San Francisco resident Anthony Costello slept through the alert but woke to the jostling.

“I was just like, ‘Oh, girl, shut up, and just rolled over,’” Costello said, who has lived in the region for eight years. “I think my sensitivity to quakes is starting to increase a little bit and also my general anxiety with quakes.”

Even still, Costello said early warnings are so important because the larger the quake, the more time you’re going to need to make sure you’re safe.

Menlo Park resident Stephanie Lucianovic also went back to sleep after a local warning prompted her phone to go off. In the morning, she discussed the quakes with her kids. She’s considering downloading the MyShake app, she said.

“I’m interested in knowing all the information, but I don’t think I’d want to have it be a loud warning every time there was some minor earthquake,” Lucianovic said.

Luckily, MyShake alerts users when there’s a 4.5-magnitude earthquake or higher, which doesn’t discount the experience of people who feel smaller quakes, like in San Ramon, where a swarm of smaller quakes has been occurring for months.

“We can’t make everybody happy,” Lux said. “Some people are going to feel it, some people may not, but we’re there to help.”