Final Results - Deep Shear Wave Velocity Profiling for Seismic Characterization of Christchurch, NZ

This project provides surface wave dispersion processing results and deep shear wave velocity (Vs) profiles for 14 sites in Christchurch, New Zealand. Each site fold within the project contains a .txt file with the 1000 "best" Vs profiles obtained from inversion of active-source (MASW) and passive-source (MAM) surface wave data collected at the site. A .pdf file that summarizes the dispersion processing results and Vs profiles is also provided within each site folder. The descriptions associated with each site folder contain DOI numbers for the archived raw data and metadata collected at each site. These data sets are part of a published project titled "Deep Shear Wave Velocity Profiling for Seismic Characterization of Christchurch, NZ - Reliably Merging Large Active-Source and Passive-Wavefield Surface Wave Methods" (https://www.designsafe-ci.org/data/browser/public/nees.public//NEES-2012-1173.groups). The analysis methods used to obtain the Vs profiles are described in Teague et al. (2017). The abstract and reference citation for this paper are provided below: Abstract: Deep (+500 m) shear wave velocity (Vs) profiles were developed at 14 sites throughout Christchurch, New Zealand, using a combination of active- and passive-source surface wave testing. The geology of Christchurch is quite complex and presents several challenges for surface wave testing. Specifically, the complex inter-layering of relatively stiff gravels with soft sands, silts, and clays makes: (1) the interpretation of experimental dispersion data ambiguous, and (2) complicates the determination of appropriate inversion layering parameterizations. In order to address (1), dispersion data uncertainty was quantified and several mode interpretations were considered during inversion. In order to address (2), 155 geotechnical boreholes and 199 geologic well logs in the vicinity of the test sites were used to guide the choice of layering parameterizations such that geologically-realistic Vs profiles were obtained via surface wave inversion. At each site, suites of 1000 Vs profiles representing the combined effects of epistemic uncertainty and apparent aleatory variability in Vs were obtained. The final Vs profiles from this study are well-constrained to a depth of approximately 500 m. At greater depths, the Vs profiles are more uncertain due to limitations of the largest aperture arrays used in passive surface wave testing. These Vs profiles have been made available on DesignSafe and are intended to aid in seismic site response analyses, including back analyses aimed at better understanding the spatial variability in ground motions experienced during the 2010-2011 Canterbury Earthquake Sequence and/or forward analyses aimed at accurately quantifying the characteristics of future design ground motions. Teague, D.P., Cox, B.R., Bradley, B., Wotherspoon, L. (2017 accepted). “Development of Deep Shear Wave Velocity Profiles with Estimates of Uncertainty in the Complex Inter-Bedded Geology of Christchurch,” Earthquake Spectra, accepted for publication.