California's earthquake early warning system alerted 3 million residents ahead of Humboldt County quake

SACRAMENTO -- California's earthquake early warning system notified about three million people about Tuesday's 6.4 magnitude earthquake in Humboldt County seconds before it struck, state officials announced Wednesday.

The California Governor's Office of Emergency Services (Cal OES) said the system, described as the nation's first, provided up to 10 seconds of notice to an estimated three million Android smartphones as well as to an additional 270,000 MyShake app users. 

Android users received the alert without using an additional app because of the state's partnership with Google to incorporate the technology on all Android smartphones. Cal OES said that since Tuesday's earthquake, there have been more than 71,000 new downloads of the MyShake app.

The early warning system is designed to allow residents a few seconds to take protective action ahead of an earthquake with a magnitude of 4.5 or greater. The technology takes data from seismic sensors and sends warnings to potentially affected areas if the projected shaking at a particular location is at a certain level of intensity.

"The single biggest threat we face to life and property in our state is a sizeable earthquake in one of our major metropolitan areas," said Cal OES Director Mark Ghilarducci in a prepared statement. "This earthquake was another important reminder for Californians to be earthquake prepared for the next big one."

Tuesday's earthquake off the Humboldt County coast struck at 2:34 a.m. southwest of Ferndale and was followed by dozens of sharp aftershocks. About 12 people were reported as suffering injuries, including a broken hip and head wound, the Humboldt County Sheriff's Office said at a news conference interrupted by a jarring aftershock. Two people died — an 83-year-old and a 72-year-old — because they couldn't get timely care for "medical emergencies" during or just after the quake.

Cal OES said the alert system's underlying technology is also being used to automate protective actions such as slowing trains, opening firehouse doors, recalling elevators, shutting off water and gas valves as well as closing bridges and gates and notifying personnel in school and medical settings.

The system was introduced in 2019, on the 30th anniversary of the deadly Loma Prieta earthquake. To date, more than 2.2 million users have downloaded California's MyShake App. More information on the earthquake early warning and earthquake preparedness can be found at earthquake.ca.gov.