Five fast facts about earthquake early warning systems

Sensors detect fast P-waves while slower, more destructive S-waves are still traveling through the earth.

Alerts may arrive seconds before shaking, but those too close to the epicenter receive little warning.

These systems detect earthquakes that have already started and are not capable of earthquake prediction.

Networks use ground motion sensors like accelerometers and seismometers to measure vibrations across the landscape.

Automated responses can slow trains, open firehouse doors, and shut off gas lines before shaking arrives.