First-Year Performance of a Nationwide Earthquake Early Warning System Using a Wavefield-Based Ground-Motion Prediction Algorithm in Japan

The propagation of local undamped motion (PLUM) algorithm is a wavefield-based method that predicts ground motions using direct observations. In March 2018, the Japan Meteorological Agency (JMA) implemented PLUM into its nationwide earthquake early warning (EEW) system, in order to enhance system robustness for complex earthquake scenarios in which traditional source-based algorithms fail to provide accurate and timely ground-motion predictions. This was the first nationwide EEW system to implement a wavefield-based methodology. Here, we evaluate the performance of PLUM during its first year of implementation in the JMA EEW system, using earthquakes that occurred between March 2018 and March 2019; these include 13 earthquakes that satisfied the public warning issuance criteria. Our analysis shows that PLUM predicted ground motions without significant errors and reduced the number of missed warnings. These findings indicate that introducing the wavefield-based methodology benefits EEW users with high tolerance of false alarms, including the general public.