"Your Guide to Earthquake Safety"

Earthquake Early Warning

The Earthquake Early Warning is a prompt announcement about the arrival time of the principal shocks and seismic intensity on the basis of the estimated place of the hypocenter and the magnitude analyzed by the observation nearest the hypocenter.

This was jointly developed by Japan Meteorological Agency, Railway Technical Research Institute and National Research Institute for Earth Science and Disaster Prevention.

If we receive the Earthquake Early Warning, we can control the train and elevator quickly and get out of danger in the factory, office and home.
This warning system makes it possible to avoid the expected danger and reduce the damage.

But the time interval from the prompt announcement of the warning till the arrival of the principal shock is more than ten to scores of seconds.
At the place near the hypocenter, the preliminary tremors and principal shocks arrive nearly simultaneously, and the prompt announcement may be too late.

Further the estimated seismic intensity sometime includes some error, because it is estimated by the data collected for very short time.

You have to understand the demerit and merit for practical use.