Japan Tsunami Warning System; Present Status and Future Plan

Abstract

The Japan Meteorological Agency (JMA) monitors seismic activity 24 hours a day using various seismographs installed throughout Japan. Most of the seismic waveform data have been telemetered to the six Regional Tsunami Warning Centers (RTWCs) which are responsible for each announced region through the dedicated telephone lines on a real-time basis.

As soon as an earthquake occurs in and around Japan, the seismic data is quickly analyzed to estimate the hypocenter and magnitude. A number of tasks such as discrimination of earthquake, P-onset detection, hypocenter determination and so forth is performed by the fully automatic procedure. If the earthquake is big enough to generate a tsunami, and has a shallow depth of focus beneath the sea floor, tsunami forecasts are issued by the RTWC(s) to the responsible coastal area within 7–8 minute after the earthquake. These forecasts are disseminated to the related organizations, the local governments, the branch offices of JMA, and the broadcasting media via computer links and/or fax devices which can send information to 100 receivers simultaneously. The tsunami warning system of JMA has been and will continue to be renewed at suitable times as new technology becomes available.