Abstract
　This paper presents the method for estimating the site amplitude amplification factors in terms of period by analyzing sufficiently large number of the JMA's low-magnification seismograph records observed during five earthquakes. The effects of earthquake factors and local soil conditions on velocity response spectra of 0.1% damping in the period range from 2 sec to 20 sec were clarified by using regression model. For regression coefficients, dummy variables representing soil condition at each site and component of records were introduced in addition to the epicentral distance. The observed spectra corrected for the geometrical spreading of surface waves and attenuation factor were compared with the predicted spectra. The statistical model presented here was confirmed to be an effective tool for predicting the velocity response spectra. It was found that the site amplification factors sometimes differ more than 10 times from the standard value and they depend strongly on period at some sites.

【キーワード】：長周期，増幅度，地域性，１倍強震計，応答スペクトル，回帰分折
Key words: long-period, amplification factor, low-magnification seismograph, response spectra, regression analysis.

*鳥取大学工学部社会開発システム工学科
Department of Social Systems Engineering, Faculty of Engineering, Tottori University