Assessing shear wave velocity profile uncertainty using multiple sCPT interpretation and processing methods

Abstract

This paper quantifies the influence of seismic Cone Penetration Test (sCPT) interpretation and processing methods on shear wave velocity (VS) profile uncertainty using data from 20 sites in Christchurch, New Zealand. The near-surface soil profiles varied across the sites, both in terms of the soils that were present and the profile layering characteristics, reflecting the depositional environment that is influenced by alluvial and coastal processes. The same experimental setup was used at each site, consisting of a dual receiver sCPT cone and a hammer source method at a consistent horizontal offset distance. Three commonly used shear wave arrival time picking methods and the cross-correlation method were used to define arrival times and time intervals between testing depths for each site. The pseudo-interval, true-interval and slope-based processing methods were used with these arrival times and time intervals to develop 11 VS profiles for each site. Alongside this, a ray tracing inversion method provided an additional VS profile at each site. The uncertainty in the VS profiles that were developed at each site are presented, highlighting the variability resulting from different processing and picking methods. Results across sites are combined to provide a representation of the uncertainty across all methods and the differences in the uncertainty across the various processing methods.