Earthquake Early Warning in Japan: 
Performance and improvements after the Tohoku earthquake

Masumi Yamada
Disaster Prevention Research Institute, 
Kyoto University

Current earthquake early warning (EEW) systems lack the ability to 
appropriately handle multiple concurrent earthquakes, which led to 
many false alarms during the 2011 Tohoku earthquake sequence in Japan. 
This paper uses a Bayesian probabilistic approach to handle multiple 
concurrent events for EEW. We improved the model to estimate earthquake 
parameters, i.e., hypocenter location, origin time, magnitude and 
seismic intensity, by using extra information which is not used before. 
Then, the sequential Monte Calro method is used to estimate the 
earthquake parameters. A real data example based on two months data 
(March 9 to April 30, 2011) around the time of the 2011 Tohoku 
earthquake is studied to verify the  proposed algorithm. Our algorithm 
results in over 90% improvement compared to the existing EEW system.