Abstract
Strong ground motions higher than 1G were recorded at HKD020 located near the source region of the 2004 Rumoi earthquake. We checked a difference of the peak periods of horizontal to vertical spectral ratio of S-waves among the main shock and the aftershocks in order to confirm frequency range affected by non-linearity of soil behavior. We compared shapes of particle motions of the accelerograms and showed good agreements between synthetic and observed particle motions at HKD020. But synthetic waveforms at the other stations were underestimated for the observed motions for the components of which amplitude are low. We conducted the parametric study for the source model and a simulation with heterogeneous propagation media to interpret a cause of the discrepancy. As a result, earthquake motions relatively far from the source region were affected by scattering of seismic wave but those near the source region can be mostly reproduced with homogeneous media.
