Detailed seismic intensity distribution was re-evaluated from the data of damage wooden houses during the 1923 Kanto earthquake in Tokyo Metropolis. The seismic intensities of most blocks were less than 5+ in JMA scale on the Yamanote terrace. They were 6+ or 7 in the east side of Sumida River in the Shitamachi lowland, while they were less than 6- in the west side even in the Shitamachi lowland because there is a buried diluvial terrace under this region. The other areas where seismic intensity was 6+ or 7 were located along the line of Kanda-Zinbo-cho, Otemachi, and Hobiya. According to the old map before more than 500 years, this line was corresponding to the old creak of Kanda River and the Hibiya inlet, where a valley was buried under the ground and alluvial soil was accumulated very thick.

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Very severe damages and disasters have been suffered from the Hyogo-ken Nanbu earthquake of January 17, 1995, and been encouraged to re-examine the earthquake proof design method on all the civil engineering structure. Taking into account for the complicated circumstances on the structure situations such as the soil conditions and the nonlinear response characteristic, it is very important to clarify these effects on the seismic response evaluations in order to enhance the safety and performance of the structure. In the present study, for the continuous pier-girder system with soil-foundations, the seismic performance evaluation is examined using the results from the nonlinear seismic response. It is shown that in order to carry out the reliable evaluations on the structure performance after severe earthquake, it is essential to clarify the structure damages by means of the seismic evaluations on multi-degrees-of-freedom system with dynamic soil-structure interaction.

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Nonlinearity of site amplification is examined by using the ground motion records of the 2001 Geiyo earthquake and subsequent smaller events. Comparisons of the site amplifications calculated from the weak and strong motion records show the nonlinear soil behavior during the main shock. The analysis of the amplification factors derived from the records of the Geiyo earthquake together with those of the 1989 Loma Prieta and 1994 Northridge earthquakes indicates that the effect of nonlinearity on peak ground acceleration becomes significant with the strain level in surface soils being larger than approximately 3×10^-4 however the nonlinear effect on peak ground velocity is not apparent up to the strain level of about 1×10^-3.

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The variance of peak horizontal accelerations and velocities of the Japanese strong-motion data set is examined. The standard errors of the data from the empirical attenuation relationships are calculated. The standard error decreases with increasing magnitude, with decreasing the distance, and with increasing the amplitude. The amplitude dependence of the error seems much stronger than the magnitude and distance dependences. The distance dependence can be caused by the effects of scattering and absorption of seismic waves in the path. The strong amplitude dependence can be interpreted by multiplying of the effects of the maginitude and distance dependences.

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