Using 3D geological models to create maps of estimated Vs30 and site period

Abstract

The 30-m time-averaged shear-wave velocity (Vs30) and the fundamental site period (T0) are useful parameters for understanding site conditions, informing geotechnical studies as well as infrastructure planning. Unfortunately, sites where this data is measured are sparse or poorly distributed, so they are not always suitable for the creation of continuous maps of these properties over an entire city. To help resolve the spatial problem, this study has used a detailed 3D geological model and assigned shear wave velocity values for the modelled subsurface material units to create maps for the Wellington City CBD of estimated Vs30 and site period. We compare the model estimated values with site calculations from surface or down-hole geophysical data and explore the variability of the model results using Monte Carlos Simulations.