Japan-France Joint Project on Strong Motion Prediction

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After the Hanshin-Awaji disaster in 1995, we strongly re-recognized the necessity of the precise prediction of strong motions by earthquakes occurred active faults beneath the high-populated cities. There are many numbers of active faults both in Japan and France, and the aim of this Japan-France joint project is how to predict strong motions during inland earthquakes both of theorctical and semi-empirical methods. To check the validity of strong motion prediction methos, we share the strong motion database about the 1995 Hyogoken-Nanbu (Kobe) earthquake, which is one of the most complete data set about not only strong motion records but source and underground structure models. We also shared several dense strong motion networks deployed at Ashigara valley, Kushiro area (Japan), and Volvi valley (EUROSEISTEST,Greece). Using those same data, we tried strong motion predictions (actually, post-diction) by several methods, compared those results, discussed about the ability and limitations of applications of those methods. As the prediction methods, we used the theoretical method (complete numerical simulations of wavefields), and semi-empirical method (empirical Green function method). To estimate site effects, we compare several methods such as traditional spectral ratio, microtremor data analysis, etc.On January, 1997, we had a small symposium about the prediction of strong ground motions at Grenoble, France. We and many rescarchers conceming to this study attended and presented their works and discuss together to get the consensus of the strong ground motion prediction now in detail and where we will go from here in the future. We made the reports which contain our works for two years and the brief report which the attendance wrote down.