Japan Earthquake Early Warning Rang 37 Million Tokyo Phones Before Ibaraki Shaking Hit

Japan earthquake early warning system delivered alerts to 37 million Tokyo-area phones before destructive shaking arrived from a M5.9 Ibaraki quake on Aug. 23, 2026. Learn how Japan’s 4,235-seismometer Cell Broadcast network works, its limitations, and how it compares to the US ShakeAlert system