[7][8] When a P-wave is detected from two (or more) of the 4,235 seismometers installed throughout Japan, the JMA analyzes and predicts the approximate location of the earthquake's epicenter.

[9] 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.

[11] In April 2011, the Chilean Subsecretary of Telecommunications said that their country hoped to establish a similar early-warning system.

Measurement techniques have since been refined to ignore minor earthquakes, and the hit rate for FY2011 increased to 56 percent.

Although EEW (Earthquake Early Warning) 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 (IPF) and Propagation of Local Undamped Motion (PLUM) methods.

[21][22] On NHK television channels and other Japanese TV broadcasters (ISDB, including 1seg),[23] an alert is a message window on the screen with the earthquake epicenter (shown as a red X with a white outline) and areas affected by strong tremors.

Nippon TV and TBS shorten it to "Kinkyū Jishin Sokuhō desu" ("This is an Earthquake Early Warning").

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 at-risk areas.

[24][25] Japan's three major mobile phone carriers—NTT docomo, au (KDDI and Okinawa Cellular) and SoftBank Mobile—have developed Cell Broadcast systems to send multiple users an SMS of the EEW.

[26][27][28] 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.

KDDI and Okinawa Cellular began free EEW broadcasts via au's SMS, C-mail (ja:Cメール), on 25 March 2008.

Japan Cablenet (ジャパンケーブルネット) (JCN) rents a receiver which notifies the user of the estimated Shindo scale and the time remaining (0 to 5 seconds).

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.

A similar, free Windows program, SignalNow Express, was made available by the Strategy Corporation (ストラテジー株式会社) after the 2011 Tōhoku earthquake.