Los Angeles County residents could be alerted to future earthquakes—potentially before shaking even begins—if they download the new ShakeAlertLA app that was released by the City of Los Angeles this week.

The app was released through a partnership between Los Angeles Mayor Eric Garcetti’s office, the city’s information and technology and emergency management agencies and is designed to work with a similar system developed by the U.S. Geological Survey and ShakeAlert, a coalition that includes the USGS and state and university partners.

ShakeAlertLA is available for download on Android and Apple smartphones. Developers say it could give users seconds or tens of seconds warning before shaking arrives at their location. Garcetti announced on Twitter that it would go live Thursday.

Earthquakes are a matter of when — not if. We're officially launching #ShakeAlertLA tomorrow, and today you can become one of the first to use our early warning technology. Download the app here → https://t.co/ePpzodn53p pic.twitter.com/XMc1aqUP90 — Mayor Eric Garcetti (@MayorOfLA) January 2, 2019

The ShakeAlert system works by using hundreds of seismometers installed up and down the West Coast that estimate the location and magnitude of a quake once shaking begins. Users of its beta system have been receiving alerts since 2012. The app is expected to be able to alert those in the affected areas before more violent shaking occurs.

The app states that users will receive a notification for earthquakes or aftershocks with magnitudes measuring over 5.0. In order to receive the alerts, users will have to allow their location services to be used by the app at all times.

It notes that users could get false or late alerts stemming from issues including being too close to the epicenter, shaking not originating from a seismic event or being too small to trigger an alert and alerts sent out due to technical errors.

The app includes features that let users see maps of recent earthquakes, including those not large enough to trigger alerts from the app, and tips for how to prepare for an earthquake and steps to take after an earthquake has occurred.

Long Beach has one prominent fault line running through it. The Newport-Inglewood fault caused the 1933 Long Beach earthquake that leveled hundreds of buildings and was responsible for over 100 deaths.

The span of destruction led state legislators to mandate stricter building codes, specifically for schools. Last year the same fault line led to the closure of Community Hospital after it was revealed that a significant earthquake could put patients at risk.