2009 年 61 巻 Supplement 号 p. 471-477
Recent studies on ground motion attenuation relations in the United States and Japan are reviewed. In the United States, the Next Generation of Ground Motion Attenuation Models (NGA) Project was initiated to develop the updated relations. In the proposed models for peaks and response spectra, effects of faulting style, hanging wall, fault top depth, nonlinear site amplification and basin depth are incorporated. In Japan, owing to recent development of strong motion instrumentation such as the K-NET, many updated attenuation relations not only for peaks and spectral response but also for instrumental seismic intensity and energy spectra have been individually developed. The terms considered in the relations are similar to those for the models of the NGA project. The variance of ground motion in the attenuation relations is also being discussed earnestly because the variance controls the results of seismic hazard analyses. Further efforts should be continued to improve the attenuation relations in response to increasing near-filed ground motion recordings and progress of theoretical studies on strong ground motion.