On an earthquake early warning system (EEW) and its applications

It is clear that the basic countermeasure against earthquake strong motion is to reinforce buildings and other structures. Realtime earthquake disaster prevention is a countermeasure during the earthquake itself and is different from realtime seismology. An EEW, earthquake early warning system, is required to trigger realtime earthquake disaster prevention. It is important to avoid too much trust in EEW for the disaster prevention. This paper describes the concept of an EEW and gives a brief history, which eventually led to the development of the UrEDAS, the urgent earthquake detection and alarm system, the first operational P-wave early warning system. A real-world example of disaster prevention by this system is described. Finally, the role of national or public organizations in earthquake disaster prevention will be discussed, with special emphasis on the situation in Japan.