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TitleGradient-based shear-wave velocity parameterization in Bayesian inversion of surface-wave dispersion for earthquake site response
AuthorGosselin, J; Dosso, S; Cassidy, J FORCID logo; Quijano, J E; Molnar, S
Source 2016.
Alt SeriesEarth Sciences Sector, Contribution Series 20160027
PublisherEuropean Seismological Commission
Meeting35th General Assembly of the European Seismological Commission; Trieste; IT; September 4-11, 2016
File formatpdf
Subjectstectonics; modelling; s waves; earthquakes; seismicity; seismic models; seismic surveys; seismic profiles; seismic surveys, ground; array seismology
ProgramPublic Safety Geoscience Western Canada Geohazards Project
AbstractKnowledge of near-surface properties of the soil column, in particular, the shear-wave velocity (Vs) profile over the upper 10s of metres, are important for characterizing the expected ground response to earthquake shaking at a specific site. Non-invasive and passive methods based on recording ambient seismic noise are increasingly popular for estimating Vs structure with minimal cost and site disruption. This paper applies a fully nonlinear Bayesian inversion methodology to estimate Vs profiles and uncertainties using surface-wave dispersion data processed from passive seismic array recordings. In the inversion, the Vs profile is parameterized using a Bernstein polynomial basis, which efficiently characterizes general depth-dependent Vs gradients in the soil column. Bernstein polynomials provide a stable parameterization in that small perturbations to the model parameters (basis function coefficients) result in only small perturbations to the Vs profile. Shear-wave velocity profiles and uncertainties are obtained from the velocity-depth marginal posterior probability density. These probabilistic Vs profile results allow for probabilistic estimates of site response factors such as peak ground velocity/acceleration and VS30. This provides a quantitative assessment of the uncertainty in site response. This methodology is applied to synthetic scenarios as well as real passive seismic array recordings collected at sites in British Columbia, Canada.
Summary(Plain Language Summary, not published)
This study presents a new development in passive-source seismology that can be used to better assess local earthquake site response. We use seismic array recordings (background noise) to determine shear wave velocity profiles a key parameter used in the National Building Code for seismic hazard calculations. Our new methodology is an improved inversion technique that allows for velocity gradients to be incorporated in the earth model, rather than just simple velocity layers. To ground-truth our technique, we compare our inversion results with known velocity profiles from nearby boreholes.

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