Abstract
Empirical relationships are evaluated to predict site amplification factors due to deep underground structure beneath engineering bedrock based on the characteristics of strong motion data which are observed in Kanto plain. As the result of estimation regarding the characteristics of strong motion data, amplification factors almost agree with the theoreti cal amplification factors estimated from the deep underground structure by Yamada (2000) in the case of coincident source and site basin locations (CBL). On the contrary, amplification is much larger than th e theoretical one in case of distinct source and site basin locations (DBL). For the difference of charact eristics between CBL and DBL, it's the reason that the mechanisms of seismic basin response de pend on the location of earthquake sources.
The relationship between the corrected factor and the basin depth is compared with the apparent incident angle of seismic motion to include the effect of the locations of the sources. The corrected factor is defined as the ratio of the amplification of the observation records divided by the theoretical amplification. The variation between the amplificati on factors and basin depth is decreased by including apparent incident angle. The equations for estimating the amplification factors which are considered from the amplification factor at the vertical incident, the basin depth and the apparent incident angle. For the validation of the evaluation, the equations are applied to Osaka Plain. The result shows that ground motion spectrums which are estimated by this study almost agree with the observed ones.
