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Testing Site-Proxy and Non-Linear Amplification Models Using Site-Specific Variability

Session: How Well Can We Assess Site Effects So Far? [Poster]

Type: Poster

Date: 4/21/2021

Presentation Time: 03:45 PM Pacific

Description: 

Variations in near surface geology have a strong effect on earthquake ground motions. Such site effects are restrained in ground-motion models (GMM) and seismic hazard assessments using site proxies. The most common site proxy is the time-averaged shear-wave velocity in the top 30m of a 1-D soil column, V_S30. We develop a GMM without any site term and only based on magnitude and distance. The site-specific variability term derived from the residuals between the prediction and observation therefore captures the local response at a site. We use this site-specific variability to evaluate site proxies and test non-linear site-amplification models. The non-linear site-amplification models are tested against a linear site-amplification model using data from the Japanese Kiban-Kyoshin network. Instead of grouping the stations by proxies, the amplification models are tested on single stations with a high number of records. The results show that site response varies greatly between sites, even within similar site proxy groups. This suggests that conventional site proxies, like V_S30, do not characterize non-linear site response sufficiently. Furthermore, for most of the stations used in the test, the linear amplification model performs better than the non-linear models. For the range of ground motions used in the test (peak ground acceleration < 0.2 g), including non-linear site amplification in ground-motion models and building codes may therefore not be justified.

Presenting Author: Karina Loviknes

Student Presenter: Yes

Authors