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Quantifying the Influence of Multi-Dimensional Effects in Site Response Analyses Using 2D and 3D Simulations in Sedimentary Basins of Wellington, New Zealand

Description: 

Several recent studies have concluded that multi-dimensional wave propagation effects can have a significant influence on site response and that 1D site-response modelling techniques often fail to capture the observed site response due to their inability to model such phenomena. This study aims to quantify the influence of multi-dimensional effects on the observed site response in the Wellington region of New Zealand by comparing results from different simulation approaches. We first discuss the effects of using various boundary conditions for modeling 2D site response at borehole arrays sites in California, including comparisons of massive column elements and free field boundary conditions using the software OpenSees at the Treasure Island Downhole Array. Then, we present results from basin modeling in the Wellington region. Amplification functions from 1D site-response analyses are compared to those from 2D site-response models and 3D physics-based ground-motion simulations to illustrate the magnitude and spatial distribution of multi-dimensional effects. Surface-to-borehole (i.e., “within”) transfer functions, which are often used in site response validation studies, are extracted from 1D and 2D site-response models to show their sensitivity to subsurface stratigraphy and surface topography. This is consistent with findings from recent global efforts illustrating that a significant percentage of sites do not display surface-to-borehole transfer functions that are consistent with those from 1D analyses.

Session: Ground Truthing Multidimensional Site Response Analyses at Borehole Array Sites

Type: Oral

Date: 4/20/2023

Presentation Time: 05:15 PM (local time)

Presenting Author: Christopher A. de la Torre

Student Presenter: No

Invited Presentation: 

Authors