Micro-tremor measurement is an easy and economical survey to know the ground vibration behavior. It was known that predominant periods estimated from micro-tremor records partially included the seismic ground characteristics. Micro-tremors were measured at 75 points in Kusatsu city of southwestern Shiga Prefecture. The predominant periods were estimated from micro-tremor records by analyzing H/V micro-tremor spectrum. And they were verified by comparing to those estimated by the conventional estimated equation and those estimated from the amplification ratio in the seismic response analysis results. The predominant periods estimated from micro-tremor records agreed with those estimated by the conventional equation and those calculated using the seismic response analysis. A zoning map of the predominant period in Kusatsu area was made on the basis of the predominant periods. A distribution of the predominant periods agreed with geological and topographical characteristics in southwestern Shiga area. Consequently, the ground seismic characteristics and the ground conditions in southwestern Shiga area were estimated.
It is very important to know the ground seismic characteristics because geotechnical damages in the earthquake are collated to the ground seismic characteristics. To investigate ground seismic characteristics, PS logging investigation using boring holes and an estimation of Swave using N-values of the Standard Penetration Tests (SPT) were performed. Recently, a micro-tremor measurement is carried out to investigate the ground seismic characteristics (Bour et al., 1998; Teves- Costa et al., 1996) because of the easiness and economical reasons. It is well known that predominant periods estimated from micro-tremor records partially included the seismic ground characteristics.
In this study, micro-tremors are measured at 75 points in Kusatsu city of southwestern Shiga Prefecture. The predominant periods are estimated from micro-tremor records by analyzing H/V micro-tremor spectrum.
