Soil profile characterization of Christchurch strong motion stations
This paper presents an overview of the soil profile characteristics at a number of strong motion station (SMS) sites in Christchurch and its surrounds. An extensive database of ground motion records has been captured by the SMS network in the Canterbury region. However in order to comprehensively understand the ground motions recorded at these sites and to be able to relate these motions to other locations, a detailed understanding of the geotechnical profile at each SMS is required. The original NZS1170.5 (SNZ 2004) site subsoil classifications for each SMS site based on regional geological information and well logs located at varying distances from the site. Given the variability of Christchurch soils, more detailed investigations are required in close vicinity to each SMS. In this regard, CPT, SPT and borehole data, and shear wave velocity (Vs) profiles in close vicinity to the SMS are currently being used to develop representative soil profiles at each site. Site subsoil classifications based on Vs measurements performed by the authors do not always agree with the original classifications, often indicating that a softer site class is appropriate. However, SPT N values often indicate a stiffer site class than the Vs data, in some cases also disagreeing with prior assumed classifications. Hence, the recent site investigation data presented herein highlights the importance of having detailed site-specific information at SMS locations in order to properly classify them. Furthermore, additional studies are required to harmonize site classification based on SPT N and Vs-.