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| | Abstract | | We installed seismometers at two sites in the intermediate and the terminal points on Miyazaki maglev test line by RTRI, and several nature earthquake data were obtained. The Miyazaki maglev test line is faced on a coastline of Hyuga-nada, and is located in the flat plain. However seismic motions observed at two sites were significantly different, nevertheless the separation distance of two sites is approximately 4km. Therefore we tried to estimate the S-wave velocity structures at these sites. To obtain the phase velocity of the Rayleigh waves, we carried out surface wave exploration and array micro-tremors observation. In addition, to improve the S-wave velocity structures, we used the predominant frequency of H/V spectral ratios. As a result, the ground conditions of the terminal site have strong contrasts of S-wave velocity in deeper layer than those of the intermediate site. It is conceivable that the significant difference of earthquake ground motions at two sites is caused by this discrepancy of site conditions. |
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