Concept of the Spectrum Conversion Factor (SCF), the ratio of the equivalent velocity (total energy input to structures) and spectral velocity (peak response velocity), is introduced and relationships between the standard deviation of phase difference (σ) and SCF are investigated. With damping, σ-SCF relations always have a positive slope, and the slopes are steeper in higher frequency band or higher damping ratio cases. In the final part of this study, three artificial ground motions compatible to design response spectra and the expected design energy spectra were demonstrated.

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Current Japanese earthquake early warning system uses data from two seismic networks: Japan Meteorological Agency (JMA) accelerometer network and high sensitive velocity-type seismometer network (Hi-net). These two datasets are processed in the different scheme and the results are merged to issue a warning. Combining these two datasets and processing in the same framework should improve the accuracy and speed of the warning. In this study, we tried to develop a method to use these two dataset in the same framework. We applied time-domain recursive filters to correct instrumental response of Hi-net sensors and adjust them to the response of mechanical seismometers. We evaluated the saturation of the Hi-net data with the data in 2 month after the Tohoku earthquake, and found the variation due to the saturation was smaller than the variation of attenuation relationship. Therefore, the Hi-net data includes important information when other data are not available yet. Speed of the warning improved by 3.6 seconds in the average for the inland earthquake by combining these two networks.

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The sheet pile wall method, a countermeasure against house subsidence and tilting induced by liquefaction, is proposed in this paper. The method is intended to prevent the house foundation ground movement due to liquefaction by installing sheet pile wall around the house foundation. The shaking table model tests, under the gravitational and the centrifugal field, were conducted, and the results indicate that it is able to reduce the house subsidence and tilting by using the sheet pile wall. In addition, effective stress analyses were conducted under various ground conditions and sheet pile length. According to these results, the effectiveness of the sheet pile wall is also confirmed.

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[in Japanese]

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