Development of deep shear wave velocity profiles in the Canterbury Plains, New Zealand

Deep (typically >1000 m) shear wave velocity (Vs) profiles were developed across the Canterbury region of New Zealand at nine strong motion stations using a combination of active and passive surface wave methods. 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 develop the Vs profiles at each site. A priori geologic information was utilized in defining preliminary constraints on the complex geologic layering of the deep basin underlying the region, including velocity reversals in locations where interbedded terrestrial gravels and marine sediments are present. Vs profiles developed as part of this study had characteristics comparable to the Vs profiles from 14 Christchurch sites detailed in a separate study. Vs profiles developed in the two studies were combined to form region specific Vs profiles for typical deposits, which can be used to improve the accuracy of current 3D crustal velocity models of the region.