SPECTRAL FORECASTING OF EARTHQUAKE GROUND MOTION USING REGIONAL AND NATIONAL EARTHQUAKE EARLY WARNING SYSTEMS FOR ADVANCED ENGINEERING APPLICATION AGAINST APPROACHING MIYAGI-KEN OKI EARTHQUAKES

摘要

Application of earthquake early warning systems (EEWSs) mainly focuses on alerting or providing information to the public services such as the emergency, fire departments, and hospitals; however, next generation EEWS will provide information to control the structures equipped with active/semi-active devices or critical systems from the destructivity of earthquake ground motion. Providing consistent and continuous spectral representation of earthquake wave amplitude for the usage of advance civil engineering applications would definitely help to reduce seismic response. Numeric simulations have been proving that structural control can be effectively achieved if the content of propagating waves is known before arriving at the building of interest. It is therefore particularly valuable to forecast Fourier Amplitude Spectrum (FAS) in this respect for real time engineering applications. In this study it is proposed that FAS of earthquake ground motion can be forecasted in far-site ranges after detection of earthquake in terms of initial ground motion, source parameters, and site amplification in frequency domain which are provided by different EEWSs. For this purpose, the authors have developed a regional warning system in Miyagi Prefecture against Miyagi-ken offshore earthquakes and integrated with the JMA/NIED, national Japan EEWS. Our system is providing a real-time online waveform data from the nearest inland point to the Miyagi subduction area to the center located in Tohoku University, Sendai. Artificial neural network methodology is utilized to integrate the information from the hybrid configuration. 39 numerical simulations have been performed for verification in the Sendai city basin where four earthquakes were selected by blind prediction using the remaining 35 recorded earthquakes in the same basin. The results indicated that the methodology of FAS forecasting will provide great contribution to structural control considering non resonance phenomena with the usage of feed forward control algorithms.