Empirical method for deriving horizontal site amplification factors considering nonlinear soil behaviors based on K-NET and KiK-net records throughout Japan

Based on the observed strong-motion records of K-NET and KiK-net, we utilized 1,065 earthquake observation stations installed throughout Japan, gathering more than 140,000 recordings for weak motions with a peak ground acceleration (PGA) less 100 cm/s2 5,300 strong PGA cm/s2. These sites detected at least one recording value greater were used to quantify horizontal-to-vertical spectral ratio (HVSR) difference between shakings. observations, discrepancy in HVSR shakings can be depicted as shift both frequency amplitude axes logarithmic coordinate system. This kind favorably interpreted by an established diffused field theory earthquakes. concept shifts, new empirical functions are proposed modify averaged linear cases order acquire nonlinear regimes. Subsequently, improved vertical amplification correction function, which considers time-averaged shear wave velocity down 30 m, was convert modified into horizontal site factor (HSAF) The methodology adopted this study, does not require detailed soil layer information, is convenient obtaining HSAF considering empirically obtained behaviors.