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The Earthquake Early Warning (EEW) (緊急地震速報 Kinkyū Jishin Sokuhō) is a warning issued when an earthquake is detected in Japan. The warnings are mainly issued by the Japan Meteorological Agency (JMA), along with guidance on how to react to the warnings.
|The alarm of the Earthquake Early Warning on TVs or radios of NHK by ja:伊福部達|
|The sign sounds of the Earthquake Early Warning by REIC|
The JMA has two Earthquake Early Warning (EEW) systems, one for the general public and another for the National Meteorological and Hydrological Services. When a P-wave is detected 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. This allows the JMA to notify 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 warn the general public when an earthquake of lower-5 or higher on the Japan seismic scale is expected. An EEW forecast (緊急地震速報(予報)) is issued to the National Meteorological and Hydrological Services when an earthquake of 3 or higher on the Japan seismic scale or 3.5 or higher on the Richter magnitude scale is expected, or when a measurement of more than 100 gals is detected in the amplitude of P-waves or S-waves.
The Earthquake Early Warning system is developed to minimize damage caused by an earthquake and allow people to take shelter or evacuate dangerous areas. It is utilised by railway workers to slow trains, and by factory workers to stop assembly lines before the earthquake reaches them.
The effectiveness of the warning depends on the position of the receiver. After receiving a warning, a person may have a few seconds to a minute or more to take action. Areas near the epicenter may experience strong tremors before a warning is issued.
Following the 2011 Tōhoku earthquake and tsunami, the EEW system, along with Japan's tsunami warning system, were considered to have been effective. Despite the tsunami taking over 10,000 lives, it is believed casualties would have been much higher if not for the EEW system.
In April 2011, the Chilean Subsecretary of Telecommunications said they hoped to establish a similar early warning system.
The JMA announced the hit rate of the Earthquake Early Warning for the 2011 fiscal year on 31 May 2012. The hit rate is defined as the percentage occurrence of the warning issued immediately upon P-waves detected having a Japan Meteorological Agency seismic intensity scale (震度 shindo) number (range 0 to 7) that falls within plus-minus 1 Magnitude-Shindo Number of ten Magnitude-Shindo Numbers measured for that earthquake.
For the fiscal years of 2007 to 2009 the hit rate was over 75%. In the 2010 fiscal year, the hit rate came down to 28% due to the number of aftershocks following the 2011 Tōhoku earthquake and tsunami, which occurred near the end of the fiscal year of 2010. The hit rate for that year had been 72% until the Tohoku earthquake. Measurement techniques have subsequently been refined to ignore small scale earthquakes; the hit rate for fiscal year 2011 increased to 56%. The JMA aimed to increase the hit rate to over 85% in the 2015 fiscal year.
Although the precision has been increasing since the operation of the early earthquake warning, there have been false alarms. The following are examples:
Technical improvements are being made to increase the hit rate. These include the use of the Integrated Particle Filter (IPF) method and the Propagation of Local Undamped Motion (PLUM) method.
The IPF method was introduced on 14 December 2016. The IPF method is a method integrally using data and methods separately used conventionally, and efficiency is improved such as seismic source elements are quickly obtained using a particle filter.[clarification needed]
The PLUM method was introduced on 22 March 2018. This is a method of predicting the seismic intensity directly from the observed intensity without estimating the hypocenter and the scale. Therefore, even when a huge earthquake occurs, seismic intensity forecast can be obtained with high accuracy. Also, since we do not estimate the hypocenter, we can predict the seismic intensity even if the hypocenter is unknown.
On NHK television channels and other Japanese TV broadcasters (ISDB including 1seg), has an alert that consists of a message window that flashes on the screen showing the earthquake epicenter and the areas affected by strong tremors. At the same time, two sets of chimes sound, after which a voice announces in Japanese:
|“||"This is an Earthquake Early Warning. Please prepare for powerful tremors." (「緊急地震速報です。強い揺れに警戒して下さい。」 Kinkyū Jishin Sokuhō desu. Tsuyoi yure ni keikai shite kudasai.)||”|
The announcement above is used by the NHK, Fuji TV, TV Asahi and Tokyo MX, whilst Nippon TV and TBS simply shorten it to "Kinkyū Jishin Sokuhō desu," or "This is an Earthquake Early Warning." TV Tokyo sound a set of chimes, but do not use a voice announcement.
These alerts also inform viewers whether or not there is a risk of a landslide or tsunami caused by the quake in the affected area. If tsunami warnings are issued, the system utilizes 1seg to automatically turn on (and tune to NHK) all radios and televisions with 1seg technology in the areas at risk. All warnings are broadcast in five languages: English, Mandarin, Korean and Portuguese, as well as Japanese.
Japan's three major mobile phone carriers, NTT docomo, au (KDDI and Okinawa Cellular) and SoftBank Mobile, have developed simultaneous broadcast systems to allow multiple users to receive an SMS telling of the EEW ('Cell Broadcast').
It is now mandatory for 3G cellular phones that were put on the market after 2007 to be able receive this service, though overseas manufacturers (Nokia, Apple, HTC, LG, Samsung, etc.) are not covered. In August 2011, Apple announced that its iOS 5 iPhone platform would support early warning notification.
EEW is enabled by default on all models of the FOMA 905i series (FOMA 905iシリーズ) released on 26 November 2007, and on some FOMA High-Speed models of the FOMA 705i series (FOMA 705iシリーズ) released in February 2008.
EEW is enabled on all models from early 2008, including W61CA, W61H, W61K, W61SA, W61SH, W62SA and a few smartphone models, such as IS02 (TSI01). KDDI and Okinawa Cellular started EEW broadcast via au's Short Message Service called C-mail (ja:Cメール) for free on 25 March 2008.
On 30 May 2007, SoftBank announced development of an EEW broadcast system similar to those of NTT docomo and au. Deployment of this system was originally planned in the fiscal year 2008 but postponed for two years. On 25 August 2010, EEW service started in all areas of the Kansai region, Tokai region, Tohoku region (seven prefectures), Chugoku region, and Shikoku region as well as limited areas of the Kanto region. The EEW broadcast network covers the whole country since 7 December 2010. As of March 2011, ja:SoftBank 831N is the only model that supports EEW, although more models are expected to support EEW after summer 2010.
RC Solution Co. developed an iPhone application named "Yurekuru Call for iPhone" to receive EEW, which is distributed on the Apple App Store for free; the application is now also available for Android. Notification of an EEW might be delayed or blocked if communication lines are congested. The Japan-localized version of iOS 5 for iPhone has built-in EEW functionality.
The specific and common chime tone from FM stations is automatically detected internally and turns on the radio (if in sleep mode) and loudly sounds a chime tone and EEW message before shaking occurs by S-waves. Once the S-wave has been analyzed, detailed information on the earthquake, such as its seismic scale and the areas under threat, is announced.
The following receivers utilize EEW broadcast from radio stations and are free of specific information fees or connection fees:
EEW radio waves can be received even in areas where no broadband Internet access is available. The quality of service, rapidity, and service area may vary from station to station.
Japanese cable TV stations offer affordable EEW services. For example, Japan Cablenet (ja:ジャパンケーブルネット) (JCN) rents out a receiver that receives EEW for advanced users and notifies the user of the estimated Shindo scale and the remaining time (0 to 5 seconds). Some cable TV stations also broadcast EEW on community radio FM and provide equipment to prefectural and municipal facilities for free.
Weathernews Inc. (ja:ウェザーニューズ), a weather information company, started a paid service to broadcast EEW for advanced users, The Last 10-Second, used by people and businesses on 15 October 2007. This service requires a computer running Windows 2000 or later with an always-on connection to the Internet and offers an affordable alternative to a costly communication terminal used exclusively for EEW. The EEW application installed on the computer can be configured to receive information on all earthquakes with a JMA magnitude of 3.5 or higher or with a seismic intensity of 3 or higher. Newer versions of the program allow for the announcement of lower-intensity earthquakes. When an EEW warning is issued, the program announces the approximate location of the epicenter, the expected JMA seismic intensity and display a countdown of when major shaking is to be expected.
On 7 July 2008, ANET Co., Ltd. (ja:ANET アネット), a disaster prevention technology company of the Railway Technical Research Institute Group, released an application, EQMessenger, to receive ANET Alert, which ciphers and broadcasts EEW information on the epicenter, the estimated seismic intensity at the user's location, and the remaining time before the arrival of the S-wave. When the estimated seismic intensity exceeds the preset level, EQMessenger can sound a warning and display the epicenter, the intensity estimation point, and the arrival of the tremor on a pop-up map.
The current Earthquake Early Warning logo used by the Japan Meteorological Agency uses a yellow catfish known as a Namazu (鯰). Many earthquake preparedness activities in Japan use the catfish as a mascot, as Japanese lore suggested that earthquakes were caused by a giant catfish making tremors, or that the sight of catfish foretold of earthquakes.