The objective of this study is to generate a nationwide map of the average shear-wave velocity in the upper 30m of the ground (AVS) from geomorphological data in order to create a more reliable groundshaking map for all over Japan. The integrated database, which consists of the AVS data obtained from borehole logs at 1,785 sites and the corresponding geomorphological data retrieved from the Digital National Land Information (DNLI) covering all over Japan, is constructed. Using the database, the relations between the AVS and the geomorphological condition are compared for three regions divided by major tectonic lines. A statistical hypothesis test for the relations reveals that the AVS in the central part of Japan tends to be lower than those in the northeast and southwest parts of Japan on several geomorphological conditions such as alluvial fan, delta and back marsh. Such regional difference of the AVS for each geomorphological condition is incorporated in a method for estimating the site amplification factor from the geomorphological data in the DNLI through the AVS. For comparison, the site amplification factor (ARV) for entire region of Japan is computed using the method proposed herein and existing methods. Consequently, the proposed method considering the regionality of the AVS can predict the AVS and the ARV in all the parts of Japan more accurately than the existing methods.
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