Does Nonlinear Soil Behavior Affect Kappa Estimates?

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: 

The high-frequency attenuation parameter kappa was introduced by Anderson and Hough (1984) to describe seismic high-frequency attenuation from ground motion records. Current research and applications of kappa focus on the linear elastic regime and understanding the relationship between kappa and other attenuation descriptors such as material damping ratio. Because soil nonlinear behavior is often triggered at soft sites subjected to strong ground shaking, the investigation of the applicability of kappa in the nonlinear regime is important. To fill the identified gap, we use the Japanese Kiban-Kyoshin network (KiK-net) database that is rich with high quality records at various site conditions to evaluate the effects of soil nonlinear behavior on kappa estimates (including individual kappa values, kappa_r and the site-specific component kappa, kappa_0). Using PGA (peak ground acceleration) and shear-strain index as proxies to capture the in-situ stress-strain relationship, linear and nonlinear ground motions are identified at selected sites of interest. The acceleration spectrum approach is used to estimate individual kappa values. Based on the identified linear and nonlinear data sets, this work studies that (1) the site-specific dependency of kappa_r on soil nonlinear behavior (e.g., comparisons between kappa_r and shear-strain index) and (2) the relationship between soil nonlinear response and the estimated site-specific component, kappa_0.

Presenting Author: Chunyang Ji

Authors