地震動のアレー観測に基づく不整形地盤の震動特性とその同定

Abstract

Powell's method to minimize a function of several variables without calculating dervativesis applied to identify the ground characteristics with irregular profiles from its recorded earth-quake motion on the ground surface. The influence of the initial values on the convergence isstudied by evaluating the square error between the given response function of one degree offreedom system and the calculated one by using the identified parameters. The identification isperformed by selecting the shear wave velocity, depth and width of irregular surficial ground asunknown parameters to obtain a least square fit over a specified frequency band between theamplitude of transfer function of two observation sites on ground surface obtained from therecorded accelerogram and the corresponding transfer function calculated from the response ofthe ground model. The discrete wave number method is used for the response analyses of theirregular ground. The dispersive trend in observed accelerograms is also explained by thecalculated response using the irregular ground model.