Abstract
We studied the spatial distribution of seismic motion characteristics at the engineering base layer of the Kanto Plain in Japan. As the index for seismic motion characteristics, the average ratio of 5% damped acceleration response spectra between the observed values and calculated values by an attenuation relation was used. By comparing the spatial distribution of the average ratios with topographical maps and geological maps, we classified the region into 8 zones. The main special features of the average ratios are as follows; (1) In the coastal lowlands, the ratios are approximately equal to 1. (2) In the loam terraces, the ratios in the short period range are large in Chiba and Ibaraki, while they are small in Tokyo and Saitama. (3) In the Sagami Plain, the ratios become large around a period of 1second by the effect of its basin structure. (4) In the areas, which are not classified into the quaternary geology, the ratios are small in the entire range of period.
