Predominant period for surface waves based on the Osaka basin model

We estimated the predominant period of surface waves from the dispersion curves of the Love and the Rayleigh fundamental mode, calculated from 1-D verlocity structure models extracted from the Osaka basin model.The estimated predominant period is from 1 to 10 s for the Love waves and 1 to 6 s for the Rayleigh waves in the Osaka plain. The linear relationships between the predominant period of surface waves and the bedrock depth are confirmed. Predominant period is proportionality to the bedrock depth. Coefficient proportionality approximately equals 5 s/Km for Love waves and 2 s/Km for Rayleigh waves. We compared the estimated predominant periods with the observed ones at strong ground motion observation stations maintained by CEORKA (Committee of Earthquake Observation and Research in the Kansai Area)for the main shock(M_J7.4)and aftershock(M_J6.5) of the 2004 off the Kii peninsula earthquake. Except for some CEORKA sites, where the depth of the bedrock is deeper than 1.5 Km, the estimated predominant period of surface waves is consistent with the observed one. This result is the first approximation,effective for the predominant period of surface waves in the Osaka plain. However,there is a possibility of a variation of the predominant period for the surface waves coming from a different direction.