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TitleProbabilistic seismic-hazard site assessment in Kitimat, British Columbia, from Bayesian inversion of surface-wave dispersion
AuthorGosselin, J M; Cassidy, J F; Dosso, S E; Brillon, C
SourceCanadian Geotechnical Journal vol. 55, no. 7, 2017 p. 928-940,
Alt SeriesEarth Sciences Sector, Contribution Series 20170045
PublisherCanadian Science Publishing
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®); html
ProvinceBritish Columbia
AreaKitimat; Douglas Channel
Lat/Long WENS-128.7333 -128.6000 54.1500 54.0167
Subjectsgeophysics; surficial geology/geomorphology; engineering geology; seismology; seismicity; seismic risk; seismic waves; s waves; seismic velocities; surface wave studies; sediments; soils; clays; bedrock geology; building codes; seismographs; field work; geophysical surveys; seismic reflection surveys; National Building Code of Canada; geological hazards; assessment; surface-wave dispersion; methodology; shear waves; classification; site amplification; ground motion; infrastructures
Illustrationstables; location maps; aerial photographs; photographs; plots; profiles; bar graphs
ProgramAssessing Earthquake Geohazards, Public Safety Geoscience
AbstractThis paper applies rigorous quantitative inversion methods to estimate seismic-hazard site classification and amplification factors in Kitimat, British Columbia, due to near-surface geophysical conditions. Frequency-wavenumber seismic-array processing is applied to passive data collected at three sites in Kitimat to estimate surface-wave dispersion. The dispersion data are inverted using a fully nonlinear Bayesian (probabilistic) inference methodology to estimate shear-wave velocity (VS) profiles and uncertainties. The VS results are used to calculate the travel-time average of VS to 30mdepth (VS30) as a representation of the average sediment conditions, and to determine seismic-hazard site classification with respect to the National Building Code of Canada. In addition, VS30-dependent site amplification factors are computed to estimate site amplification at the three Kitimat sites. Lastly, the VS profiles are used to compute amplification and resonance spectra for horizontally polarized shear waves. Quantitative uncertainties are estimated for all seismic-hazard estimates from the probabilistic VS structure. The Kitimat region is the site for several proposed large-scale industrial development projects. One of the sites considered in this study is co-located with a recently deployed soil seismographic monitoring station that is currently recording ground motions as part of a 5 year campaign. The findings from this work will be useful for mitigating seismic amplification and resonance hazards on critical infrastructure, as well as for future seismological research, in this environmentally and economically significant region of Canada.
Summary(Plain Language Summary, not published)
Knowledge of near-surface properties of the soil column, in particular, the shear-wave velocity (Vs) profile over the upper 10¿s of metres, are important for characterizing the expected ground response to earthquake shaking. In this study we improve upon non-invasive and passive techniques that use recordings of ambient seismic noise (and so are low-cost, fast and minimise site disruption). We apply an advanced inversion methodology to estimate Vs structure and uncertainties from surface-wave recordings made on a seismic array. This new methodology is applied to passive seismic array recordings collected at five sites in Kitimat, British Columbia, Canada and we compare our inversion results from several sites to active-source reflection data collected nearby.