Evaluation of Magnitude, Hypocenter Distance and Subsurface Soil Effect to Spatial Variability of Ground Motions between Adjacent Sites

Abstract

Effects of magnitude, hypocenter distance and subsurface soil structure on the spatial variability of ground motions between adjacent sites are examined using observed records from the Chiba array and pairs of the K-NET and the KiK-net which are adjacent to each other. The statistical analysis of coherence and standard deviation of Fourier spectrum ratio of the ground motion show that the spatial variability of ground motion depends on magnitude, distance and subsurface soil structure. In particular, subsurface soil structure has the most significant influence on the variability. The decrease in S-wave velocity of subsurface soil causes a reduction of spatial coherence. And we also found that the longer the distance between observation sites, the deeper the soil properties effects to the spatial variability of ground motions.