ESTIMATION OF SHEAR WAVE VELOCITYSTRUCTURE USING ARRAY OBSERVATION OFSHORT PERIOD MICROTREMORIN KOSHIGAYA CITY, JAPAN

摘要

In this study, Spatial Autocorrelation Method (SPAC Method) was carried out in Koshigaya City,Saitama Prefecture, Japan. Additionally, we applied H/V spectral ratio or Nakamura method to thesame area. We obtained that in the western part of the study area the engineering bedrock(Vs>400m/sec) is as shallow as 10-15 m, where as in the eastern part it is much deeper and reaches to50-60m. The former is categorized in Class D or Stiff Soil of NEHRP (2001) Ground Classification,and the latter in Class E or Soft Soil. We could obtain the same soil classification by implementing themethod proposed by Kon'no et al. (2007), which allow us to skip the inversion of the dispersion curve. Finally, H/V spectral ratio could not show any correlation of its predominant period withthe underground velocity structure determined by SPAC method. Furthermore, with the providedinformation from Nakamura method it is difficult to obtain the ground classification at a site.