It's still beyond the reach of science to predict exactly when an earthquake will strike, but Japan will soon get the next-best thing — televised warnings that come before the shaking starts.

In an ambitious attempt at protecting large populations from seismic disaster, the Meteorological Agency and NHK are teaming up to alert the public of earthquakes as much as 30 seconds before they hit, or at least before they can bring their full force down on populated areas.

The system — the first of its kind in the world — cannot actually predict quakes, but officials say it can give people enough time to get away from windows that could shatter, or turn off ovens and prevent fires from razing homes.

And in one of the most earthquake-prone countries in the world, every second counts.

"If we can give people enough time to take even a few steps to protect themselves before the shaking starts, it could help reduce injuries and damage," agency spokesman Makoto Saito said.

The warnings, to begin in October, will be based on data provided by the Meteorological Agency, which maintains an intricate network of sensors deep underground that estimate the intensity of a quake as soon as the ground ruptures.

Alarms can go out before the shaking starts because there is a lag between the time it takes for different seismic waves to travel to the surface.

Japan, which sits atop four tectonic plates, has been hit by 83 temblors strong enough to cause injury since March 1996, including one last month that killed 11 people and caused a fire and small radiation leak at the world's largest nuclear power plant.

The warning system works by detecting primary waves, which spread from the epicenter of a quake and travel faster than the destructive shear waves. When waves of a certain intensity are detected, the alarms are set off. NHK will relay them almost instantaneously to its television and radio audience.

The agency started issuing warnings last August to more than 500 organizations, including power companies and railways.

The system is not perfect.

Lightning or other interference can cause it to transmit false alarms, for example, and early warning won't work for areas directly above the ruptured fault because the two waves it detects are nearly simultaneous.

Residents who are not watching television or listening to the radio when an alert goes out will not hear it.

Still, the agency says the system helped it issue a tsunami alert for a magnitude-6.9 earthquake in northern Japan in March two minutes faster than its old early warning system would have. The agency was also able to put out a warning ahead of last month's magnitude-6.8 quake that hit Niigata Prefecture.

How the larger public will react has been a concern.

"Chaos and injuries could result, for example, if an urgent earthquake warning is sent to a facility with large numbers of customers and a crush forms at the exits as people rush to get out," an agency study group wrote in a report last year.

The warnings, it was decided, must come with explanations of what viewers can do — stop cars and elevators, get away from things that can fall and, most of all, protect their heads.

"We realized the warnings won't work if confusion is the result," said the agency's Saito. "The public needs to be educated about how and how not to react."

Since early last month, NHK has begun preparing the nation for the alerts, running promotional spots accompanied by skits that show how to respond.

Officials say the system is unprecedented in scale, and may serve as a model for others.

"A lot of the injuries in an earthquake come from secondary damage, like fires started from open gas lines," said Barry Drummond, who oversees seismic monitoring for Canberra's Geoscience Australia. "If you've got enough time to shut the gas valve, you're that much farther ahead."

Small-scale warning systems exist in parts of Mexico, Taiwan and Turkey. In the United States, commercially available, battery-powered seismic gadgets can warn a limited region, while a group of seismologists at the University of California, Berkeley, is working on a system inspired in part by the one in Japan.

"The implementation in Japan is most important to us as a test of the concept," said Richard Allen, who heads the group. "We are particularly interested to see how the public reacts to the information and (who) starts to make use of the information and how."