ShakeAlertLA also has LA-specific information about how to prepare for and get help after a major quake.

ShakeAlertLA deploys a warning to smartphones when shaking is expected anywhere in Los Angeles County

Los Angeles has become the first city in the U.S. to deploy an earthquake early warning system for the public.

The app, called ShakeAlertLA, uses a network of seismic sensors distributed throughout the region to detect earthquakes and deploy a warning to smartphones when shaking is expected anywhere in Los Angeles County.

It was developed by Mayor Eric Garcetti’s office in partnership with the U.S. Geological Survey, AT&T, and the Annenberg Foundation.

More details are expected Thursday, when Garcetti will make an official announcement about the app at City Hall. But the app is already available to download in the Apple and Android app stores.

In addition to the warning, the app features maps of recent local earthquakes and LA-specific information about how to prepare for and get help after a major quake.

Screenshots from the ShakeAlertLA show how Angelenos will receive advance warnings for earthquakes.

In last year’s State of the City address, Garcetti promised that an early warning app would be in the hands of Angelenos by the end of 2018. A handful of local organizations like Metro, NBCUniversal, and LAUSD have already been using the real-time ShakeAlert data. In Metro’s case, the agency conducts regular drills where trains are slowed or stopped, which could prevent derailments in large earthquakes.

Other countries like Mexico and Japan have had similar systems in place for years. These apps have been credited with preventing serious injuries and deaths in advance of major quakes.

For more than a decade, the USGS has worked with a group of universities and research institutions to secure funding and build out the sensor network for the Shake Alert program, which distributes the seismic data to the City of LA’s app. The initial goal of the Shake Alert system was to create an early warning system for the entire West Coast, but federal dollars to pay for development were repeatedly zeroed out during budgeting.

Hunter Owens, the city’s data scientist, noted on Twitter that the app’s code has been made open-source for other cities or states to use.

Another early warning app in development by Santa Monica-based Early Warning Labs which also uses Shake Alert data has been shared with a group of beta-testers, some of whom have received up to 30 seconds of warning for recent earthquakes.

That beta app, named QuakeAlert, features a customized, location-based countdown depending on how far away the user is from the earthquake’s epicenter. The ShakeAlertLA app does not appear to have a countdown feature.

After the state’s most devastating wildfire season, where evacuation notices and other wireless alerts intended to save lives did not reach people who were in danger, early warning systems have been heavily scrutinized by officials who worry that only some people will get the alerts. Even established earthquake early warning systems like Japan’s have issued false alarms.

One of the biggest challenges for an app like ShakeAlertLA is relying on existing smartphone carriers to quickly deliver the warning using cell networks which are easily overwhelmed. Last year, the city of LA partnered with AT&T to allow more than 48,000 city employees to test the beta alerts locally.