This paper discusses the characteristics of amplification in subsurface layers, based on records on earthquakes observed at three locations on filled ground in the Osaka Bay area, with different ground conditions. In analyzing and determining the amplification characteristics, earthquake scale and propagation route were taken into consideration, referring to earthquake motions in the base rock of mountains surrounding Osaka Plain, and those in the diluvial layer 60 m under the surface of the filled ground. It was found that the amplification characteristics of eathquake motions in the filled ground vary conspicuously according to the structure of subsurface layers, up to approx. 60 m under the surface. It is particularly noteworthy that the damping effect of the Hedoro layer, between relatively hard layers, is very strong.
