Abstract
S-wave records for 17 earthquakes observed by a dense accelerograph array (Chiba array) are analyzed to investigate the source, path and site effects on polarization of strong ground motion. The polarization characteristics averaged over the array do not agree with those expected from the focal mechanism because of the wave scattering effect along the path. The direction of the average polarization varies with frequency, and the degree of the average polarization decreases with increasing in the earthquake magnitude and the hypocentral distance. Each of the observation points shows its own local site effect on polarization of strong ground motion. It is suggested that the local site effect is caused by some anisotropic property of the surface layers at the Chiba array site.
