A simialr wanring system is also When the magnitude 9.0 earthquake was detected in Japan, automatic systems sent an earthquake early warning alert to the public. When two seismometers detect the P-waves from an earthquake, the Japan Meteorological Agency immediately analyzes the readings and distributes the warning before the arrival of S-waves.
The Japanese earthquake early warning alerts are widely broadcast over radio, television, Internet, text messages, mobile phone apps, and other devices. The alerts interrupt any programs to let people know how strong the shaking will be, the count down until the shaking starts, and the current estimate of the size of the earthquake. This provides people time to duck under a solid object (like a desk) and to hold on before the shaking starts.
Around the San Francisco Bay Area in California, the San Francisco Bay Area Rapid Transit (BART) has installed a similar earthquake early warning system. This system will automatically brake trains when an earthquake is detected to allow trains to slow down before the ground starts to shake.
Watch these videos to learn more about Earthquake Early Warning - ShakeAlert: Earthquake Early Warning System; Earthquake Early Warning: Pacific Northwest subduction zone