COMPARISON BETWEEN SPECTRAL CHARACTERISTICS EVALUATED FROM STRONG MOTIONS AND MICROTREMORS AT STRONG-MOTION SITES IN YOKOHAMA

Abstract

Spectral characteristics of strong motions and microtremors are compared at the dense strong-motion network sites in Yokohama. From strong motions, spectral ratios are evaluated by dividing Fourier amplitude spectra in the horizontal component by reference spectra which are obtained from strong motions on exposed soft rocks (SMSR). From microtremors, horizontal-to-vertical spectral ratios are obtained (HVSR). Good correlation is found between the fundamental periods of SMSRs and HVSRs especially on the condition that less site-amplification sites are excluded. Good correlation is also found between the spectral peak amplitudes of SMSRs and HVSRs (As and Ap, respectively) and the relationship is regressed as As=0.87Ap.