Characterization of a Reclaimed Site and Its Seismic Vertical Amplification

Abstract

In this paper an analysis is presented for the field observation of large amplification in vertical motion at a reclaimed site subjected to the 1995 Kobe earthquake. The observation is considered to be associated with the amplification of P-waves caused by incomplete saturation of shallow soils. Saturation effects of soils on P-wave velocity and Poisson's ratio are discussed to show evidence of partial saturation in shallow layers at the array site. An analytical study is described to demonstrate substantial influence of saturation on the amplification of a soil layer to vertical earthquake excitation. Furthermore, a numerical simulation of the vertical motion at the realistic site considered and is performed by incorporating saturation effects of shallow soils. The present study indicates that vertical motions may significantly be affected by saturation of surface soils, suggesting that one may need to carefully examine this soil condition in the study of vertical site amplification.