Abstract
An optimization technique under the unconstrained condition was introduced into earthquake engineering for the purpose to elucidate dynamic characteristics of the ground and building during an earthquake. In this report a main effort was paid for the estimation of the underground structure at SMAC site in Hachinohe city, where a very strong motion had been recorded at 1968 Tokachi-oki earthquake. Known quantities are a couple of seismic records at the free surface and at 50m in depth. Structural parameters to be optimized are S wave velocities and Q values. Flows of optimization procedure are illustrated in Figs. 5 and 6. Optimal spectral ratio between two seismometer positions shows a good agreement to that by the observation (see Fig.7). Physical meaning of the results by this technique was also investigated.
