A Study on an Empirical Formula for Amplification Factor Based on Fundamental Peak Frequency and Amplitude of Microtremor H/V

Abstract

We propose an empirical formula expressed by using indices of microtremor H/V in order to easily evaluate an amplification factor for peak ground velocity in consideration of an effect of input motion spectra for bedrock. Firstly, an empirical formula model for an amplification factor consisting fundamental peak frequency and peak amplitude is derived based on a theoretical model proposed by authors. It is found that the empirical formula can accurately evaluate the amplification factors. Next, a formula for amplification factors evaluated from observation records is obtained by using parameters of site effect. The observed amplification factors show strong correlation to the ones evaluated by the formula. Finally, we develop an empirical formula by using a microtremor H/V instead of the site effect. Consequently, it is clarified that the empirical formula can evaluate the observed amplification factors more accurately than the formula model in the past studies.