Abstract
For years, earthquake ground motion has been observed at 6 stations in Kamakura city, Japan. Among them, two stations of NMD and ONR have been found to show larger vertical motion. Especially at NMD, a maximum acceleration ratio between vertical and horizontal motions is sometimes exceeds 1, with a constant predominant period of about 0.25sec for both vertical and horizontal motions. A 2-D BEM is applied to characterize ground motion at both stations, with a result showing that steep slopes of bed rocks under the surface layers play important but different roles for both cases.
