| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1997: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1996: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
The forward prediction model of ground motion integrating source, site and propagation characteristics has been developed using wave propagation theory and source kinematics. The refined model of wave propagation path from source to site is expressed as the multi-layred half-space which consists of a surface layr overlying a semi-infinite random medium. The source rupture process is expressed as the summation of the slip functions to subevents which develop in compliance with a degree of the random heterogeneity on the fault surface. The physical laws and key parameters have been presented to describe essentially the waveform, spectral characteristics, site amplification, the effective mechanism radiating short period waves, and the directivity of the source radiation. In this paper, the prediction potential of the ground motion model is examined through a simultaneous simulation test against the recorded seismograms of ground motion at sites KBU(Kobe University, the Committee of Earth
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quake Observation and Research in the Kansai area), KEN(Kansai Electric Power Co. Inc.), and MAT(Matsumura-gumi Technical Research Institute)during the Hyogo-Ken Nanbu earthquake of January 17,1995. They are strongly conditioned by not only the site amplification but also by the source dynamics because these sites are located just above the faulting region. The soil sediment structures and geological structures of basement crust for these sites were investigated by a seismic reflection survey, observed weak ground motions, PS logging and boring data. The geological profiles in and around Kobe City are fan-shaped, consisting of thick surface layr with a fault-like irregular boundary, dipping from north to south, and overlying basement bedrock^4. In this prediction test, the surface soil sediment and basement bedrock beneath each recording site in Kobe City are idealized by a multi-layred half-space overlying a semi-infinite random medium. The Green's functions from the discrete source points on the fault surface to each site are calculated precisely according to the geological data. Seliguchi et. al. estimated the slip vectors distribution to describe the source rupture process by solving the inverse problem for the observed ground motion. In this study, the prediction potential of the ground motion model is investigated through a simultaneous simulation test using the seismograms at the KBU,KEN,and MAT sites. The synthetic ground motion at the three sites are expressed by their Green's functions of the multi-layred half-space and the single source function which is described by slightly modifying the slip vectors distribution by Sekiguchi et. al.. The synthetic ground motions agree well with the observed ones at all the sites in the waveforms and response spectra. Less
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