ESTIMATES OF LOCAL SITE EFFECTS BY A GENERALIZED INVERSION SCHEME USING OBSERVED RECORDS BY “SMALL-TITAN”

A generalized inversion scheme to separate the effects of source, propagation path and local site from S-wave spectra was applied to “Small-Titan” records obtained in the Sendai region, North East Japan. Site amplification factors estimated from the generalized inversion scheme vary significantly, reflects the effects of soil characteristics at each site: strong site-dependency was found in the site amplification factors. Results from the generalized inversion scheme are compared with those obtained by the direct spectral ratio scheme, the H/V method and the bootstrap inversion. There is a good agreement in the amplification factors between them. The H/V method for estimating site amplification is found to extract the same predominant periods as the other methods. This paper especially emphasizes a good agreement in not only predominant periods but also amplification factors. Estimated source spectra and Qs-value were also in an agreement with results of previous studies by others.