A fundamental study on 3D effects of irregular ground on seismic ground motions based on observation records and FEM analyses

抄録

In irregular ground where engineering bedrock is inclined, seismic ground motions are locally amplified due to interference between body waves and surface waves generated secondary. In irregular ground where bedrock inclined in multiple directions, seismic ground motions may be more significantly amplified not only by 2-D effects but also by 3-D effects. In this study, we obtained the seismic observation records on actual irregular ground and tried to clarify the 3-D amplification effect of seismic motions by FEM analyses. Although we observed in a narrow area of about

300 m, we found large differences not only in the duration and maximum acceleration of the seismic records, but also in the peak frequency and peak magnification of their spectral ratios (at each site / bedrock outcrop site). We compared the transfer function of the 1-D ground with spectral ratios evaluated from the 2-D or 3-D analyses and confirmed that the amplification of seismic motions due to the 3-D effect of the irregular ground is significant at the ground.