Earthquake Early Warning (Japan)


In Japan, an Earthquake Early Warning is a warning issued when an earthquake is detected. The warnings are primarily issued by the Japan Meteorological Agency, with guidance on how to react to them.

Introduction

The JMA has two EEW systems: one for the general public and another for the National Meteorological and Hydrological Services. When a P-wave is detected from two of the 4,235 seismometers installed throughout Japan, the JMA analyzes and predicts the approximate location of the earthquake's epicenter. This allows the JMA to notify people in affected prefectures by TV and radio if a strong earthquake is expected.
An Earthquake Early Warning is issued to warn the general public when an earthquake of 5 or higher on the Japan seismic scale is expected. An EEW forecast is issued to the National Meteorological and Hydrological Services when an earthquake of 3 or higher on the Japan seismic scale is expected, or when the amplitude of P- or S-waves measures more than 100 gals.
The system was developed to minimize earthquake damage and enable people to take shelter or evacuate dangerous areas before the arrival of its strong surface waves. It is used by railways to slow trains and by factories to halt assembly lines before the earthquake hits.
The effectiveness of the warning depends on the position of the receiver. After receiving a warning, a person has from a few seconds to a minute or more to take action. Areas near an epicenter may experience strong tremors before a warning is issued.
After the 2011 Tōhoku earthquake and tsunami, the EEW system and Japan's tsunami warning system were considered effective. Although the tsunami killed over 10,000 people, it is believed that the casualties would have been much higher without the EEW system. In April 2011, the Chilean Subsecretary of Telecommunications said that their country hoped to establish a similar early-warning system.

Hit rate

The JMA announced the Earthquake Early Warning hit rate for the 2011 fiscal year on 31 May 2012. The hit rate is the percentage of warnings issued immediately on the detection of P-waves with a Japan Meteorological Agency seismic intensity scale number within one shindo number of the measured earthquake.
For the fiscal years 2007–2009, the hit rate was 75 percent or higher. The 2010 hit rate fell to 28 percent, due to the number of aftershocks following the 2011 Tōhoku earthquake ; before the earthquake, the hit rate was 72 percent. Measurement techniques have since been refined to ignore minor earthquakes, and the hit rate for FY2011 increased to 56 percent. The JMA intended to increase the hit rate to over 85 percent by FY2015.

Inaccuracies

Although EEW accuracy has been increasing, the following erroneous alarms have been issued:
Technical improvements are being made to increase the hit rate, including the Integrated Particle Filter and Propagation of Local Undamped Motion methods. The IPF method, introduced on 14 December 2016, obtains seismic source elements with a particle filter. The PLUM method, introduced on 22 March 2018, predicts the seismic intensity directly from observed intensity without estimating the hypocenter and scale. Accurate seismic-intensity forecasts can be made for large earthquakes or those whose hypocenter is unknown.

Broadcast format

Television

On NHK television channels and other Japanese TV broadcasters, an alert is a message window on the screen with the earthquake epicenter and areas affected by strong tremors. Two sets of chimes sound, followed by a voice announcement in Japanese: "This is an Earthquake Early Warning. Please prepare for powerful tremors." In addition to NHK, the announcement is used by Fuji TV, TV Asahi and Tokyo MX. Nippon TV and TBS shorten it to "Kinkyū Jishin Sokuhō desu". TV Tokyo sounds a set of chimes, without a voice announcement.
The alerts also inform viewers of possible landslides or a tsunami caused by the quake in the affected area. If tsunami warnings are issued, the system utilizes 1seg to automatically turn on all radios and televisions with 1seg technology in at-risk areas. In addition to Japanese, the warnings are broadcast in English, Mandarin, Korean and Portuguese.

Mobile-phone networks

Japan's three major mobile phone carriers—NTT docomo, au and SoftBank Mobile—have developed Cell Broadcast systems to send multiple users an SMS of the EEW.
It is mandatory for 3G cell phones sold after 2007 to receive this service, although foreign manufacturers such as Nokia, Apple, HTC, LG and Samsung are exempt. In August 2011, Apple announced that its iOS 5 iPhone platform would support EEW notification.

NTT docomo

EEW is enabled by default on all models of the FOMA 905i series released after 26 November 2007, and on some FOMA high-speed models in the FOMA 705i series released after February 2008.

au

The system was enabled on all models in early 2008, including :ja:W61CA|W61CA, :ja:W61H|W61H, :ja:W61K|W61K, :ja:W61SA|W61SA, :ja:W61SH|W61SH, :ja:W62SA|W62SA and a few smartphone models, such as :ja:IS02|IS02. KDDI and Okinawa Cellular began free EEW broadcasts via au's SMS, C-mail, on 25 March 2008.

SoftBank Mobile

On 30 May 2007, SoftBank announced development of an EEW broadcast system similar to NTT docomo's and au's. Deployment of the system was originally planned for FY2008, but was postponed for two years. On 25 August 2010, EEW service began on Shikoku, in the Kansai, Tōkai, Tōhoku and Chūgoku regions, and portions of the Kantō region. The EEW broadcast network has covered the whole country since 7 December 2010. The :ja:SoftBank 831N|SoftBank 831N was the only model supporting EEW in March 2011, although more models had been expected to support the system after summer 2010.

Other

RC Solution Company developed Yurekuru Call for iPhone, a free iPhone application to receive EEW which is distributed on the Apple App Store; the application is also available for Android. Notification of an EEW might be delayed or blocked if communication lines are congested. The Japanese version of iOS 5 for iPhone has built-in EEW functionality.

Radio

A specific, common chime tone from FM stations is automatically detected and turns on the radio, sounding a loud chime and broadcasting an EEW message before the quake begins by detecting S-waves. When the S-wave has been analyzed, detailed information on the earthquake is announced.
The following radios receive EEWs from radio stations and are free of information or connection fees:
EEW broadcasts can be received in areas without broadband Internet access. Signal quality, speed and service area may vary from station to station.

Stations

Japanese cable TV stations offer EEWs. Japan Cablenet rents a receiver which notifies the user of the estimated Shindo scale and the time remaining. Some cable-TV stations also broadcast EEWs on FM community radio stations and provide free equipment to prefecture and municipal facilities.

Internet

, a weather-information company, began a paid EEW service on 15 October 2007. The service requires a computer running Windows 2000 or later with an always-on connection to the Internet. The EEW application can be configured to receive information on 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. The program announces the approximate location of the epicenter, the expected JMA seismic intensity and displays a countdown to expected major shaking.
ANET, a disaster-prevention technology company which is part of the Railway Technical Research Institute Group, released an application to receive ANET Alert on 7 July 2008. This deciphers and broadcasts EEW information on the epicenter, the estimated seismic intensity at the user's location, and the time remaining 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, intensity estimation and the arrival of the tremor on a pop-up map.
A similar, free Windows program, SignalNow Express, was made available by the Strategy Corporation after the 2011 Tōhoku earthquake.

EEW-capable devices

The Earthquake Early Warning logo used by the Japan Meteorological Agency is a. Many earthquake-preparedness activities in Japan use the catfish as a mascot; in Japanese mythology earthquakes were caused by a giant catfish, or seeing catfish foretold an earthquake.