Early-warning system sent alert before South Napa earthquake

PASADENA, Calif. (KABC) -- An experimental earthquake early-warning system for California worked as expected during the South Napa quake Sunday. The system sent out an alert 10 seconds before the ground started shaking.

The system works by measuring primary waves which move through the Earth at almost twice the speed of a quake's destructive S waves and actually shake the ground. The system sounds an audible alert, shows a countdown timer and estimates the intensity of an earthquake.

The notice all depends on how far away you are from the quake. It could be one second or up to a minute. Still, scientists say it would be a valuable tool to protect lives and property, giving people time to power down infrastructure and run for cover.

Seismologists say that once the technology advances, they should be able to faster determine a quake's magnitude and send that information out to the public before the strongest shaking waves reach your location.

California is working to implement a statewide system. The system is not fully operational because of a lack of funding and some technical kinks scientists are still working out. The system costs at least $32 million to build and $16 million a year to operate.

"It's not a public system right now, so only a small group of test users, about 150, get it, but if we were to turn this into a public system, then everybody could get it on their cell phones so they could duck, cover and hold on and reduce the amount of damage or injuries that occur during an earthquake," said Richard Allen, director of the University of California, Berkeley, Seismological Laboratory.

The alert was only sent to a few select amount of people Sunday, mainly scientists and researchers. Japan and Mexico have similar early-warning systems.

The Associated Press contributed to this report.