Earthquake early warning system in Japan

Keiji Doi
1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan.
Tel. : +81-3-3212-8341 ext. 4505,
Fax: +81-3-3212-2857,
E-mail: keijidoi@met.kishou.go.jp

Abstract:
The Japan Meteorological Agency (JMA) is the unique agency in the government of Japan which is responsible for issuing earthquake information. Seismic intensity values measured automatically with seismic intensity meters and a location and a magnitude of an earthquake obtained by analysis of seismic data from the nationwide observation network are made public immediately after earthquake occurrence on a real-time basis 24 hours a day and seven days a week.

In order to enable proper and immediate emergency response of authorities of the national government and of municipalities in case of disastrous earthquakes the JMA issues the following successive information:

• about two minutes after the event: prompt report of seismic intensities with names of areas where the maximum seismic intensity is 3 or above;
• about five minutes after the event: information on a hypocentre and a magnitude of the earthquake;
• about ten minutes after the event: information on seismic intensities at stations where seismic intensities are one or above.