抄録
Accelerograms from the 1993 Noto-hanto-oki earthquake (MJMA=6.6) are simulated at four sites with different ground conditions by using a semi-empirical method for modeling the earthquake faulting stochastically. Seismic moment M0 and fault plane for the main shock are determined from a tsunami source model. Two element events, whose focal mechanisms are similar to that of the main shock, are selected among four large aftershocks of MJMA=5.0-5.1. Source spectra of these events follow the ω-2 model and their corner frequencies fCE are equal to or higher than those expected from the M0-fC relation by BOORE (1986). Synthesized records are in good agreement with observed ones in both cases of using these element events on the condition that standard deviations SD of displacement on the fault plane are assumed to be about five times as large as those for other large events whose source spectra follow the ω-2 model. The higher value of SD suggests that high frequency components of seismic waves were strongly excited due to some large heterogeneity of displacement on the fault plane of the main shock. This result is also supported by the fact that maximum accelerations from this event observed at stations within an epicentral distance of 200km are systematically larger than those from the 1984 Nagano-ken-seibu earthquake (MJMA=6.8), which has almost the same seismic moment as this event.