Not Forecasting: How Japan's Earthquake Early Warning System Works

When a major earthquake strikes, every second is precious for saving lives. Japan, one of the world’s most earthquake-prone nations, has successfully developed advanced technology known as the Earthquake Early Warning System (EEWS). The technology can send alerts to citizens’ mobile phones and automatically halt high-speed trains even before the main seismic waves reach the surface. How does the science behind this rapid system work? Mitsuyuki Hoshiba, a researcher from the Meteorological Research Institute of the Japan Meteorological Agency (JMA), explained the details. When tectonic plates shift and trigger an earthquake, two primary types of seismic waves are generated. This is where technology steps in. Because electronic communication signals (such as the internet and mobile networks) travel at the speed of light—far quicker than seismic waves moving through the ground—the system can alert the public several seconds before the major shaking (S-waves) arrives at their location. “Communication travels much faster than seismic waves. That’s why warnings can be sent ahead of strong shaking,” Hoshiba stated during the Geohazard 2026 webinar on Monday, 18 May 2026, according to BRIN. Although the warning time is only a few seconds, this brief period is crucial for citizens to take cover under a table or evacuate their homes. The key to Japan’s system success lies in its extensive infrastructure. The country has approximately 4,400 seismic monitoring stations spread across various regions. This sensor network operates 24/7 to detect real-time vibration activity. Once sensors detect the initial waves, data is instantly processed by computers to estimate the earthquake’s epicentre and the expected intensity of shaking. Notably, the alert system appears on television screens, radios, citizens’ phones, and public address systems, and is also directly integrated with industrial machinery and public transport sectors. One of the most successful applications is in the Shinkansen high-speed rail network. “When sensors detect an earthquake, the system automatically cuts power and activates emergency brakes before the major shaking reaches the tracks. All processes occur automatically without waiting for operators,” Hoshiba explained.