A map from Metrolink’s Commuter Railway Seismic Interface digital interface marks the location of all Metrolink trains at the time of the earthquake.
On Monday, April 14, a 5.2 magnitude earthquake struck near the city of Julian in San Diego County initiating a real-world response from Metrolink’s cutting-edge Early Earthquake Warning (EEW) system. The first-of-its-kind innovation integrates our onboard Positive Train Control (PTC) system with U.S. Geological Survey ShakeAlert technology, enabling earthquake detection sensors to communicate real-time, location-based data directly with our trains.
The ShakeAlert-powered EEW system also has the ability to stop or slow trains automatically when dangerous conditions are present. On April 14, three trains on Metrolink’s San Bernardino Line were halted by automated PTC braking, marking the first time this capability has been used to bring trains to a full stop. Additional trains on the Orange County, Inland Empire-Orange County and 91/Perris Valley lines received informational alerts or were directed to reduce their speed based on the severity of the shaking in their area. The system continued to feed relevant information to trains operating across Metrolink’s service network throughout the initial earthquake and a series of aftershocks of various magnitudes.
The unique interface between ShakeAlert and PTC adds a critical layer of protection by reducing the time between detection and response and ensuring responses are customized for each Metrolink train. Furthermore, PTC’s ability to automatically slow or stop trains when ground motion exceeds a specific threshold significantly reduces the risk of derailments or injury to passengers and crews.
Earthquakes are a part of life in Southern California, with more than 10,000 seismic events recorded each year, hundreds of which exceed a magnitude of 3.0. That constant threat is exactly why Metrolink has prioritized earthquake preparedness through innovation and planning. Thanks to a $4.8 million Caltrans grant awarded in 2019, we were the first railroad in the nation to implement an operational ShakeAlert-integrated braking system, which fully launched in 2023. We also test our safety protocols regularly and take part in large-scale emergency simulations like the annual Great California ShakeOut. These efforts ensure both staff and riders are ready to respond when the ground moves—just as they did during the recent San Diego County quake.