The ShakeAlertLA app is an earthquake early warning system that detects significant earthquake activity and is supposed to alert residents 48 seconds before the shaking hits. But after Thursday’s 6.4 earthquake hit, many people who had downloaded the app were wondering why they didn’t receive a notification.
Seismologist Dr. Lucy Jones said the ShakeAlert computer system at Caltech’s seismic lab registered a 48-second warning that shaking had begun, but the warning signal did not go out to the public.
When the ShakeAlert system works correctly, sensors placed by the U.S. Geological Survey in certain fault lines detect the earthquakes. Alerts, that work much like an Amber Alert, are then sent to mobile phones across the area.
