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Capturing Epistemic Uncertainty in Site Amplification Models with Different Site Proxies, Including Geomorphological Sediment Thickness

Description: 

Local geological features can have a strong impact on earthquake ground shaking. Especially sites with softer sediments, which are expected to amplify the recorded ground motion. However, estimating this site amplification at new sites and sites without any direct geotechnical measurements of site parameters remains a large challenge in seismic hazard assessment. In this study we propose adopting a geomorphological model for inferred sediment depth (Pelletier et al., 2016), as an alternative site proxy to predict ground motion site-amplification on a regional or global scale. Though originally developed as an input for hydrology and ecosystem modeling, the global inferred sediment depth model is is based on a combination of data including topographic slope, geological maps and water table depth, which correlate with geotechnical soil conditions known to yield seismic amplification.

To test the suitability of the geomorphological model for ground-shaking prediction, we compare the ability of the new proposed proxy and common site proxies to predict site amplification using empirical site amplification derived for sites in Europe at regional scale. We find that the geomorphological sedimentary thickness performs better than or equally well as the traditional regional-scale proxies, such as VS30 inferred from topography. We therefore argue that the inferred geomorphological sedimentary thickness from the Pelletier et al. 2016 model is a promising new alternative for predicting site amplification on a regional or global level. Furthermore, the differences in the predicted site amplification maps from different proxies captures the epistemic uncertainty associated to the site amplification models used in large scale seismic hazard or risk studies. This result has important implications for the development of new generation of ground-shaking models used for shake maps and regional seismic hazard and risk models.

Session: Understanding and Modeling the Uncertainties in Earthquake Ground Motions [Poster]

Type: Poster

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Karina Loviknes

Student Presenter: Yes

Invited Presentation: 

Authors