The study on standard of rock reference site

The method of rock reference site spectral ratios is commonly used to analysis site effects, and it is facing an issue on how to select rock reference site. Generally, the average shear-wave velocity has become a standard parameter for quantifying site response at a site. However, soil site effect shows uncertainty with V_s³⁰ criterion, due to amplification effect of rock reference site itself. The present article suggests various selection standard of rock reference site, such as two parameters, V_s³⁰ and the site predominant frequency (f₀) are used to select rock reference site. Using strong motion recorders from the KiK-net Japanese database and based on each site horizontal-to-vertical spectral ratios and surface over depth spectral ratio, the variability of the estimated rock reference site response for five different categories, according to V_s³⁰ and f₀ values, are compared. The results demonstrate that with selection standard of rock reference site of V_s³⁰ or f₀ can lead to a corresponding wide variety in site amplification, and with V_s³⁰ and f₀ two parameters it significantly reduces the variability to the amplification and the amplified frequency band of the rock response. In the end, this criterion is thus proposed as selection standard of rock reference site.