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Quantifying Site Amplification for Seismic Hazard in a Complex Shallow Basin: Case Study of the Wellington Basin, New Zealand.

Description: 

A global challenge for the seismological community is the treatment of complex local site/basin effects in urban seismic hazard analysis. Gobal global ground motion models (GMMs) and associated Vs30-based site models have been shown to perform well overall in New Zealand, forming a robust foundation for the national seismic hazard model (NSHM). However, it is widely recognised that the treatment of site response based on the single site metric of Vs30 is limited. This is evident when such models are applied to basins where significant localised amplification effects occur, such as the Wellington Basin, New Zealand.

To further the goal of more fully capturing site/basin amplification in future iterations of NSHM, the New Zealand NSHM team are using the Wellington Basin as a case study to explore and compare different modelling methods. We will present an overview of the basin study including basin characterisation and exploration of (i) NSHM site models, ii) site-to-site residuals (site terms) with respect to NSHM GMMs (iii) HVSR/SSR analysis and iv) physics-based ground motion modelling techniques. Particular challenges are posed in the Wellington Basin due to small-scale and relatively complex local structure that generates significant, but spatially variable amplification in the 0.5 to 2s period range. Nonlinear effects may also be influential at the softest soil sites for larger earthquakes that dominate the hazard.

Session: Site-specific Modeling of Seismic Ground Response: Are We Quantitative Enough to Predict?

Type: Oral

Date: 4/19/2023

Presentation Time: 11:30 AM (local time)

Presenting Author: Anna E. Kaiser

Student Presenter: No

Invited Presentation: 

Authors