LOS ANGELES – A smartphone app launched Thursday by Los Angeles Mayor Eric Garcetti is the first publicly available app in the nation that can alert Los Angeles city and county residents if a major earthquake has struck, potentially granting precious seconds for people to evacuate and prepare.

The free app, called ShakeAlertLA, works in tandem with the United States Geological Survey’s earthquake early warning system.

The app can be downloaded on a smartphone under any carrier plan, although the early warning system works only for individuals who live in or are working in Los Angeles County when an earthquake strikes.

If an earthquake of 5.0 magnitude or greater strikes, the alert system sends a push notification, not a text message, to your phone.

Garcetti praised the app Thursday at a City Hall press event as a critical, life-saving tool in the city’s larger emergency-response plans.

“This is really about precious seconds,” Garcetti said. “We believe it will make Angelinos safer.”

But Garcetti urged residents to use the app in conjunction with analog disaster-preparedness plans, such storing food and water. He stressed that the app, which can send alerts either in English or Spanish, does not have a countdown feature to tell you when shockwaves will reach you.

A screenshot of the ShakeAlertLA smartphone application launched Thursday in Los Angeles shows the app’s emergency alert features, such as an epicenter map and a list of disaster aid resources. (Photo courtesy of the Office of the Mayor of Los Angeles.)