Overview of Site Effects and the Application of the 2022 New Zealand NSHM in the Wellington Basin, New Zealand

• DOI: 10.1785/0120230189
• Publication Date: 2024-01-24T06:22:34Z
• Authors: Anna Elizabeth Ka...; Matt P. Hill; Chris de la Torre; Sanjay Bora; Elena Manea; Liam Wotherspoon; Gail M. Atkinson; Robin Lee; Brendon Bradley; Anne Hulsey; Andrew Stolte; Matt Gerstenberger
• Keywords: Subsoil

ABSTRACT We provide an overview of the treatment site effects in New Zealand National Seismic Hazard Model (NZ NSHM), including a case study basin central Wellington. The NZ NSHM 2022 includes change parameter from subsoil class (NZS class) to VS30. Poor VS30 characterization is major source uncertainty NSHM; however, advanced Wellington allows for in-depth study. First, we construct regional 3D shear-wave velocity model and maps parameters (T0, NZS class, VS30) At city soil sites, find ratios hazard spectra with respect current equivalent design range factors ∼0.8–2.6 (median ∼1.5), depending on local conditions spectral period. Strong amplification peaks at 0.5–2 s are observed Linear site-specific amplifications multiple methods compared 13 stations well-defined by both site-to-site residuals response relative station POTS. many deeper soft sites (VS30<300 m/s), strong occur around T0 that underpredicted mean ergodic ground-motion (GMM) predictions. This underprediction slightly enhanced when using basin-specific Z1.0 as additional parameter. Our highlights outstanding challenges modeling within shallow basins NSHMs, need consider region- or approaches well nonlinear high shaking intensities dominate hazard. For Zealand, general, illustrated study, priority further (and VS) seismic network better isolate quantify uncertainties allow useful exploration regional–GMM adjustments partially nonergodic approaches.