Development of Two-State Nonlinear Site Amplification Model for Japan Dependent on Vs30 and Fundamental Period of Soil

Session: Near-Surface Effects: Advances in Site Response Estimation and Its Applications [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

We present a two-stage nonlinear site amplification model that considers both time-averaged shear wave velocity down to 30 m depth (V_S30) and fundamental period (T₀) of soil. Adopting a non-reference site approach, empirical site amplification ratios for 1,591 Kyoshin and Kiban Kyoshin network sites are developed. This process involves analyzing 92,025 surface ground motion recordings from 305 earthquakes occurred between 1997 - 2012. The model is developed in two stages: first, we regress the total empirical site amplification ratios in terms of V_S30; second, we fit a functional form to the residuals from the first stage using T₀ of the site. We validate the model through residual analyses and statistical methods. We found that the first stage site term reduces the error at mid-to-long period ranges (> 0.1s) by 0.11 from the error of the initial site term without any constraints. The second stage site term reduces the error further as 0.06. We observe that soil nonlinear effects increaseT₀ and decrease the peak of amplification with increase of equivalent shear strain (I_γ). We discuss the model limitations and applicability range of the predictor variables.

Presenting Author: Dong Youp Kwak

Authors