On the 30th anniversary of the Loma Prieta earthquake, California plans to introduce an early-warning earthquake system with the ambitious agenda of buzzing the cell phones of anyone in a danger zone.

The first-in-the-nation program, to begin Thursday, taps an emerging network of motion sensors across the state to identify a major quake before people feel any movement. Then, it sends out a text-message notice in the affected areas, similar to an Amber Alert, as much as 20 seconds before serious shaking begins.

Scientists have long dreamed of having the technology to provide advance earthquake notice, even if it’s just a few precious moments, so people can step out of an elevator, stop a surgery or duck under a desk. While state officials say the new warning system is still a work in progress, they say it’s evolved to the point where it can save lives.

“Now is as good of a time as any to make this live,” said Ryan Arba, chief of the Seismic Hazards Branch of the California Office of Emergency Services. “We’re committed to doing everything we can to protect people from the dangers of earthquakes.”

How to get the MyShake a pp The early-warning earthquake app can be downloaded for free at Apple’s App Store and Google Play. It will be operable starting Thursday.

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The warning system is the result of a years-long partnership among the state, UC Berkeley, the California Institute of Technology and the U.S. Geological Survey.

In addition to providing Wireless Emergency Alerts, which are currently used not only for Amber Alerts but notices about wildfires and extreme weather, the partnership is launching a statewide mobile app that delivers similar earthquake warnings with more detailed information.

Titled MyShake, the app will be available for download Thursday and will also provide notifications of earthquakes of lesser danger.

Cell-phone alerts will be issued only when the system’s sensors detect a quake with a magnitude greater than 5.0 and a complex set of algorithms projects the shaking will cause significant damage. Just a couple such temblors hit California each year.

Alerts via the MyShake app will go out for earthquakes that exceed 4.5 magnitude and to areas projected to have minor shaking, about what would be felt in a building struck by a truck, said Richard Allen, director of UC Berkeley’s Seismological Laboratory and one of the architects of the warning system.

“That’s been a question. What should the thresholds be?” Allen said, noting that the app is a good option for people wanting knowledge of a quake even if it’s not a major threat. “We’re trying to strike the right balance.”

The amount of notice people get, either on the app or by cell phone, depends on their distance from the earthquake’s epicenter. The developers say that if the Loma Prieta earthquake were to hit today, as it did in the Santa Cruz Mountains 30 years ago, San Francisco residents would get about 15 seconds of advance warning. Marin County residents would get 17 or 18 seconds.

The 1989 temblor, which had a magnitude of 6.9, caused major infrastructure damage, including the collapse of part of the Bay Bridge, and famously interrupted the World Series between the San Francisco Giants and Oakland A’s at Candlestick Park.

The warning system, the developers say, can help prevent such losses, allowing, for example, fire stations to open their doors before they might get stuck, energy companies to shut off high-risk equipment and BART to slow down trains.

Scientists say there’s a 2 in 3 likelihood of another 6.9-magnitude quake hitting the Bay Area over the next 30 years.

“We have to be ready for an earthquake like Loma Prieta tomorrow,” Allen said.

The new warning system has been tested over the past several years, with increasingly positive real-world results. The developers have been able to generate advance notices for several recent earthquakes, including the 2014 Napa quake.

Since June, the California Office of Emergency Services has provided about $1.5 million for the project, piggybacking on five years of startup funds from state and private foundations. An additional $7.6 million will be spent to promote the app, state officials said.

“Nothing can replace families having a plan for earthquakes and other emergencies,” Gov. Gavin Newsom said in a prepared statement. “And we know the big one might be right around the corner. I encourage every Californian to download this app and ensure your family is earthquake ready.”

Kurtis Alexander is a San Francisco Chronicle staff writer. Email: kalexander@sfchronicle.com Twitter: @kurtisalexander