The effect of soil propertyies on seismic amplification is discussed with emphasis on soil nonlinearity based on vertical array records for the main shock and aftershocks of the 1995 Hyogoken Nanbu earthquake. Clear dependency f average spectral amplification is confirmed not only on the Vs-ratio between base and surface but also on the base acceleration probably due to soil nonlinearity effect. Soil nonlinearity affecting the site amplification tends to be very large within about 30m from the surface during a severe shaking and below that depth moderate nonlinearity is exerted down to about 100m. Equivalent linear analyses may still be applicable to such strng nonlinearity if appropriate equivalent properties cna be chosen. For a site with deep bed rock, reliable damping evaluation in a deep ground is of utmost importance for reliable site amplification evaluation.
展开▼
