Earthquake Early Warning (Japan)
 The alarm of the Earthquake Early Warning on TVs or radios of NHK by |
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The sign sounds of the Earthquake Early Warning by REIC |
The Earthquake Early Warning (EEW) (緊急地震速報 Kinkyū Jishin Sokuhō?) is a warning issued when an earthquake in Japan is detected. The warnings are issued mainly by the Japan Meteorological Agency (JMA), along with guidance on how to react to the warnings.
The JMA has two Earthquake Early Warning schemes. One is for the National Meteorological and Hydrological Services and the other is for the general public. When there is a P-wave detection from any two or more of the 4,235 seismometers installed throughout Japan, the JMA automatically analyzes and predicts the rough area of the earthquake's epicenter. These rough predictions allow the JMA to warn people in affected prefectures through TV and radio if strong shaking is expected.
An Earthquake Early Warning alert (緊急地震速報(警報)) is issued to the general public when an earthquake of Japan seismic scale "5-lower" or higher is expected. An Earthquake Early Warning forecast (緊急地震速報(予報)) is issued to the National Meteorological and Hydrological Services when an earthquake of Japan seismic scale 3 or higher, or magnitude 3.5 or more is expected, or when a measurement of more than a 100 gals is detected in the amplitude of P-wave or S-wave.
The Earthquake Early Warning is set up to help people in minimizing damages caused by an earthquake: people may take shelter or move away from dangerous areas such as cliffs. Railway workers use this warning to slow down trains, and factory workers may use it to stop assembly lines before the shaking reaches them.
The effectiveness of a warning depends on the position of the receiver. After receiving a warning, a person may have few seconds to a minute or more to take action. Areas near the epicenter may experience strong tremors before any warning.
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