不規則構造に対する地震波の挙動 : その2.1944年東南海地震による静岡県太田川下流域浅羽町付近の被害について

概要

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The distribution of damage due to the 1944 Tonankai earthquake at Asaba-Cho cannot be explained by the current vibration theory which inevitably assumes the horizontal parallel layers. We took into account the real subsoil structures and interpreted this problem from the viewpoint of elastic wave theory utilizing the finite element method. This area is apposite for our purpose, since the detailed data associated with the soil conditions and the damage are available. We considered the cases of vertically incident SH and SV waves. It was found from the calculated seismograms that the secondary generated surface waves from a part of the inclined layer were evident. These surface waves strongly affect the ground motion in addition to the body waves reverberating in a horizontal layer, especially near Toyozumi where the greatest damage was sustained in this area. A good correlation was found between the relative seismic energy obtained from the seismograms at each site and the relative damage percentage (percentage of totally destroyed wooden houses). After all, the difference of damage is explained by the level of the contribution of secondary generated surface waves at the irregular structures to the ground motions.
1982-03-31