SUMMARYThis study clarified the effects of measurement noise on identification of soil properties from vertical array observation of seismic waves. In order to evaluate the sensitivity of the unknown parameter with respect to error caused by noise, the amplitude of a transfer function was used to formulate the evaluation function in the frequency domain. Also the logarithmic amplitude was used to formulate the evaluation function and compare the sensitivity between the two types of amplitude expressions. A numerical experiment, based on a simple-structured ground model, showed that these evaluation functions produced satisfactory results which were in good agreement with identified results obtained by the measurement data contaminated by artificially generated errors. The present theory, when applied to actual earthquake records, proved useful in evaluating the influence of the non-linearity of soil characteristics.