J-Alert

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title: "J-Alert" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["emergency-management-in-japan", "emergency-population-warning-systems", "2007-establishments-in-japan", "2007-introductions"] description: "Japanese disaster alert system" topic_path: "geography/japan" source: "https://en.wikipedia.org/wiki/J-Alert" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Japanese disaster alert system ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/6/66/J-ALERT_Image3-en.svg" caption="Diagram of the J-Alert system"] ::

J-Alert (; full name ) is the early warning system used in Japan. J-Alert was launched in February 2007. The system is designed to quickly inform the public of threats and emergencies such as earthquakes, severe weather, and other dangers. The system was developed in the hope that early warnings would speed up evacuation times and help coordinate emergency response.

System

J-Alert is a satellite based system that allows authorities to quickly broadcast alerts to local media and to citizens directly via a system of nationwide loudspeakers, television, radio, email, and cell broadcasts. According to Japanese officials, it takes about one second to inform local officials, and between four and twenty seconds to relay the message to citizens. An enhanced version of the J-Alert receivers were installed by the end of March 2019. The new models can automatically process the information within two seconds, compared to the older models that can take up to twenty seconds.

J-Alert broadcasts via both ground systems and the Superbird-B3 communication satellite.

When there is a civil emergency such as a ballistic missile heading towards Japan, a siren called Civil Protection Siren sounds across loudspeakers.

Information transmission capabilities

::figure[src="https://upload.wikimedia.org/wikipedia/commons/0/0a/J-Alert_Message.jpg" caption="North Korean missile launch over Japan"] ::

• Earthquake
  • Earthquake Early Warning
  • Quick updates on hypocenter, magnitude, and precautions of possible tsunami
  • Information of hypocenter, magnitude, intensities of various areas, and the presence of tsunami
  • Earthquake prediction warning for the Tōkai earthquakes
  • Earthquake prediction advisory information of the Tōkai earthquakes
  • Earthquake prediction information of the Tōkai earthquakes
• Tsunami
  • Major tsunami warning
  • Tsunami warning
  • Tsunami advisory
• Volcano eruption
  • Emergency warning of volcanic eruption and the possibility of eruption
  • Warning of volcanic eruption and the possibility of eruption
  • Volcanic crater forecast
• Severe weather
  • Emergency warnings for heavy rain, heavy snow, gale, snowstorm, waves, and storm surge
  • Warnings for heavy rain, heavy snow, gale, snowstorm, waves, and storm surge
  • Weather advisory
  • Information of the risk of landslides
  • Advisory information for tornado
  • Information of violent heavy rain
  • Flood forecast
• Special emergency threats
  • Information of ballistic missiles
  • Information of airstrikes
  • Information of guerrilla and special forces attacks
  • Information of large-scale terrorism
  • Other information for civil and national defense

Adoption rate

Many prefectures and urban areas were slow in adopting the system. Upon its introduction, the Japanese government hoped to have 80% of the country equipped with the J-Alert system by 2009. However, by 2011, only 36% of the nation had been covered. Cost had been a major factor; the initial installation is estimated to be around 430 million yen, and the yearly maintenance is estimated to be around 10 million yen.

By May 2013, 99.6% of municipalities nationwide were covered.

Notable instances

• On 13 April 2023, a North Korean missile launch warning led residents to take cover from debris that most likely fell into the sea hundreds of miles away. The alert, just before 8 a.m., triggered sirens on Hokkaido and sent automated messages to mobile phones in J-Alert urging the northern island's more than five million residents to seek immediate shelter, after Pyongyang fired a new type of ballistic missile.

References

References

1. "J-Alert: disaster warning technology in Japan – Centre for Public Impact".
2. "Japan Launches Alert System For Tsunamis And Missiles".
3. "Jアラートの概要".
4. (7 August 2017). "Disaster agency urges municipalities to upgrade J-Alert receivers".
5. (2021-04-17). "東京都地域防災計画".
6. "Protecting Ourselves against Armed Attacks and Terrorism".
7. (31 October 2013). "J-alert to serve as early warning system during weather emergencies". The Japan Daily Press.
8. Kelly, Tim. (2023-04-13). "Japan stands by cancelled missile alert sent to millions of residents". Reuters.

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::