Theme Lecture – Tools for Quantifying Uncertainties Associated with Non-Invasive Subsurface Site Characterization Methods used for Seismic Ground Response Analyses
B. Cox, Professor, Civil and Environmental Engineering Department, Utah State University, USA
Numerical earthquake wave propagation simulations, known as ground response analyses (GRAs), are commonly performed in an attempt to estimate the site-specific, frequency-dependent amplification of seismic waves (i.e., site effects) as they travel from a reference bedrock condition up through soil layers to the ground surface. The importance of accurately predicting site effects for engineering infrastructure projects in seismically active regions cannot be overstated. One-, two-, and three-dimensional (1D, 2D, and 3D) GRAs have been developed to simulate the complexity of the subsurface and seismic wave propagation patterns. However, the overwhelming majority of GRAs are presently performed using only 1D simulations. While 3D GRAs are theoretically plausible, they remain largely inaccessible in research and practice due to a lack of adequate and affordable site characterization methods that can be used to develop 3D subsurface shear wave velocity (Vs) models down to depths required for ground response studies (i.e., engineering bedrock). This presentation will detail several different non-invasive seismic site characterization methods that can be used to develop subsurface models for use in 1D, 2D and 3D GRAs. Specifically, methods such as horizontal-to-vertical spectral ratios (HVSR or H/V) of ambient noise, multi-channel analysis of surface waves (MASW) and microtremor array measurements (MAM) will be discussed, and open-source tools for implementing these methods and quantifying uncertainties will be provided.