Development of Deep Site Specific and Reference Shear Wave Velocity Profiles in the Canterbury Plains, New Zealand

Deep (typically >1000 m) shear wave velocity profiles were developed across the Canterbury basin at nine strong motion stations using a combination of active and passive surface wave methods and horizontal to vertical spectral ratio measurements. A multi-mode, multi-method joint inversion process, which included Rayleigh and Love wave dispersion and horizontal to vertical spectral ratio data, was used to estimate the shear wave velocity profiles at each site. A-priori geologic information was utilized in defining preliminary constraints on the complex geologic layering of the Canterbury basin. At sites where interbedded layers were present, velocity reversals were considered in the inversion. Shear wave velocity profiles developed as part of this study were combined with the median profiles from 14 Christchurch sites detailed in a separate study, to develop a suite of region and soil specific reference shear wave velocity profiles for the Canterbury basin. Site specific and reference shear wave velocity profiles developed as part of this study can be used for back-analysis of earthquake ground motions, forward analysis of future ground motions, full 3D physics based simulations, or to refine 3D velocity models for the region.