New California earthquake alert system can warn you seconds before shaking starts

People across California can receive earthquake warnings seconds before they feel shaking through a new cell phone alert system starting Thursday, the 30th anniversary of the Loma Prieta earthquake.

State officials are scheduled to announce the new alert system Thursday morning at the Bay Bridge, which partially collapsed during the deadly 1989 quake.

The project has been in the works for years and relies on sensors buried throughout the state as part of the ShakeAlert system, a collaboration of researchers at UC Berkeley, the United States Geological Survey and the California Institute of Technology.

Californians can receive the notifications through the cell phone application MyShake, which has been available for download for months, although before Thursday was not equipped to transmit early warning alerts.

The farther a person is from the epicenter, the more time they’ll likely have before the shaking reaches them.

Californians right above the epicenter of an earthquake likely won’t receive advance warning, said Richard Allen, director of the UC Berkeley Seismological Laboratory. Those who are warned will have a short amount of time to move away from windows and brace themselves.

It takes about eight seconds for the ShakeAlert system to detect a quake and about four seconds to broadcast an alert to phones, Allen said. It will send alerts for earthquakes over magnitude 4.5, according to the state’s Office of Emergency Services.

Had the application been live during the Loma Prieta quake, which began near Santa Cruz, those at the World Series game in Candlestick Park would have had a 15-second warning before the stadium began to wobble, according to estimates from researchers.

This will mark the first time residents across California can receive earthquake alerts through their phones. Los Angeles residents were already able to get alerts through a different app, ShakeAlertLA. It comes several months after two big earthquakes originated in Ridgecrest, prompting Gov. Gavin Newsom to declare a state of emergency, and just days after a series of smaller earthquakes shook the Bay Area.

The MyShake app also collects shaking data from phones during quakes and transmits it back to scientists at Berkeley. It allows people to report about their experience during an earthquake, including how much shaking they felt and how much damage they observe.

Mexico and Japan have had early warning systems for earthquakes in place for years. Those countries are located near subduction zones under the ocean, where one of the earth’s tectonic plates is sliding below another, meaning most of those countries’ earthquakes originate offshore.

California’s earthquakes are caused by two plates sliding past one another. That means most California quakes originate beneath dry land where people are already living, making it more difficult to design an early warning system that gives residents adequate notice to take cover.

“That’s the key difference, and that’s the reason it’s taken longer,” Allen said.

About 25,000 people have already downloaded the application, but the state’s Office of Emergency Services aims to raise that number to 4 million over the next year. Newsom and the Legislature included $7.6 million in the budget for a public information campaign that will encourage Californians to sign up for the app and learn more about earthquake safety at

The early warning alerts are currently only available in English through the smartphone app. State officials are working on expanding early alerts to other platforms so people who don’t use smartphones can also receive advance warning, said Ryan Arba, chief of seismic hazards at the California Office of Emergency Services.

Making the alerts available in other languages is also a top priority, Allen said.

“I think we can feel pretty good about the fact that we have one of the most significant early warning systems in the world,” he said.

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Sophia Bollag covers California politics and government. Before joining The Bee, she reported in Sacramento for the Associated Press and the Los Angeles Times. She grew up in California and is a graduate of Northwestern University.
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