A Study on the Site Amplifications Estimated by Generalized Inversion Technique

Abstract

Strong ground motions are composed of source terms, path effects, and site amplifications. These are well known characteristics for strong ground motions. Generalized inversion technique (GIT) proposed by Andrews (1982) is an effective tool to evaluate the characteristics. In this study, first we collected the waveforms distributed by NIED (K-NET, KiK-net), JMA (87-type and 95-type), and CEORKA from 1988 to 2016 and performed GIT by using the Fourier amplitudes of their waveforms. We confirmed that the characteristics estimated by GIT were stable and match the theoretical model as shown in the previous study. As for the site amplifications, we found that we could explain the S-wave site amplifications estimated by GIT with 1D-theory, and that the full-wave site amplifications have some correlation with AVS10 (average S-wave velocity of top 10m), AVS30 (average S-wave velocity of top 30m), AVSz (average S-wave velocity of the sediments), and Tz (travel time of the sediments). We also found that the site amplifications recalculated by using the whole duration of the waveforms could explain the predominant period in sedimentary basins in Kanto and Kinki areas.