NONLINEAR SEISMIC RESPONSE AND SOIL PROPERTY DURING STRONG MOTION

Abstract

During the 1995 Hyogoken-Nambu earthquake, strong acceleration records were obtained at several sites in and around Kobe city. At some of these recording sites, multi-level vertical arrays had to been installed, which demonstrated very peculiar nonlinear features of seismic amplification in reclaimed land areas and Holocene and Pleistocene deposits. The down-hole acceleration records on Port Island where one of the strongest accelerations was measured, have been analyzed with the inversion technique to estimate S-wave velocity and damping ratio corresponding to the main shock as well as a small aftershock. Records of three other down-hole sites with much different distances from the epicenter between them were also analyzed with the same technique. These studies disclosed effects of soil liquefaction and nonlinear soil properties on the peculiar seismic amplication mechanism at these sites.