Introduction
The JMA has two Earthquake Early Warning schemes; one is for advanced users, another for the general public. Upon P-wave detected by any two or more out of 4,235 seismometers installed throughout Japan (as of 1 April 2010), JMA automatically analyzes and predicts the rough area of epicenter and warns people in prefectures through TV and radio if strong shaking is expected.
Earthquake Early Warning (alert)(緊急地震速報(警報)) is issued to general public when Japan seismic scale 5-lower or more is expected. Earthquake Early Warning (forecast)(緊急地震速報(予報)) is issued to advanced user when Japan seismic scale 3 or more, or magnitude 3.5 or more is expected, or 100 or more gal is detected in amplitude of P-wave or S-wave.
The timing of a warning depends on conditions when a warning can be issued and received. After receiving a warning, a person may have a few seconds or in some cases significantly longer to take action, but if the epicenter is very close there may be cases in which strong tremors come ahead of any warning.
The Earthquake Early Warning is set up to enable people to mitigate damage from an earthquake: people may protect themselves at home, at the office, and near cliffs. Railway workers may use this warning to slow down trains, and factory workers may use it to stop assembly lines prior to an earthquake.
Following the 2011 Tōhoku earthquake and tsunami, the early warning system, along with Japan's tsunami warning system, was considered effective by Indian scientist Dr. Shailesh Nayak, who helped develop India's warning system, though the tsunami nonetheless killed over 10,000 people.
In April 2011, the Chilean Subsecretary of Telecommunications will disclose to implement similar Earthquake Early Warning system utilized in Japan through ISDB-T.
Read more about this topic: Earthquake Early Warning (Japan)
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