Influence of Epistemic Uncertainty in Shear Wave Velocity on Seismic Ground Response Analyses

Passeri, Federico; Foti, Sebastiano; Cox, Brady R.; Rodríguez-Marek, Adrián

doi:10.1193/011018eqs005m

Cited by 37 publications

(18 citation statements)

References 47 publications

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“…They confirm that the geophysical equivalence in the V R -f and V S,z -z spaces implies the equivalence in terms of the dynamic response of the deposit. Indeed at least the first two resonance peaks (which are also the most relevant for seismic response evaluations) are very consistent among the whole set of equivalent solutions, coherently with similar findings in the literature (Foti et al 2009;Comina et al 2011;Griffiths et al 2016;Teague and Cox 2016;Teague et al 2018;Passeri et al 2019a). The higher resonance frequencies are more dispersed in the case of La Salle-1 site (Fig.…”

Section: Inversion Procedures and Shear Wave Velocity Profilessupporting

confidence: 88%

“…An identification and quantification of uncertainties associated with the EDC is not straightforward. Indeed, the influence of different uncertainty sources converges into the EDC and a precise distinction between them is most often unfeasible (Teague and Cox 2016;Passeri et al 2019a). For this reason, the uncertainties in the EDCs are usually jointly modelled via the overall COV V R as a function of frequency (Lai et al 2005;Foti et al 2014).…”

Section: Uncertainties In the Edcmentioning

confidence: 99%

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The Polito Surface Wave flat-file Database (PSWD): statistical properties of test results and some inter-method comparisons

Passeri

Comina

Foti

et al. 2021

Bull Earthquake Eng

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The compilation and maintenance of experimental databases are of crucial importance in all research fields, allowing for researchers to develop and test new methodologies. In this work, we present a flat-file database of experimental dispersion curves and shear wave velocity profiles, mainly from active surface wave testing, but including also data from passive surface wave testing and invasive methods. The Polito Surface Wave flat-file Database (PSWD) is a gathering of experimental measurements collected within the past 25 years at different Italian sites. Discussion on the database content is reported in this paper to evaluate some statistical properties of surface wave test results. Comparisons with other methods for shear wave velocity measurements are also considered. The main novelty of this work is the homogeneity of the PSWD in terms of processing and interpretation methods. A common processing strategy and a new inversion approach were applied to all the data in the PSWD to guarantee consistency. The PSWD can be useful for further correlation studies and is made available as a reference benchmark for the validation and verification of novel interpretation procedures by other researchers.

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Section: Inversion Procedures and Shear Wave Velocity Profilessupporting

confidence: 88%

Section: Uncertainties In the Edcmentioning

confidence: 99%

The Polito Surface Wave flat-file Database (PSWD): statistical properties of test results and some inter-method comparisons

Passeri

Comina

Foti

et al. 2021

Bull Earthquake Eng

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“…While this approach still relies on 1D GRAs with assumed laterally homogeneous subsurface layers, the combined result of all randomly generated Vs profiles can reproduce wave scattering effects (Nour et al, 2003). However, this method relies on stochastic probabilistic modeling approaches and requires site-specific input parameters that are not typically available, bringing additional uncertainty to the predictions (Passeri et al, 2019;Teague et al, 2018). This uncertainty can be significant, and blind Vs randomization has been shown to yield unrealistic Vs profiles that lead to poor site response predictions (Griffiths et al, 2016a(Griffiths et al, , 2016b that are different than ground motions recorded at downhole array sites (Teague et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

An H/V Geostatistical Approach for Building Pseudo-3D Vs Models to Account for Spatial Variability in Ground Response Analyses I: Model Development

Hallal¹,

Cox²

2020

Preprint

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Many recent studies have shown that we are generally unable to accurately replicate recorded ground motions at most borehole array sites using available subsurface geotechnical information and one-dimensional (1D) ground response analyses (GRAs). When 1D GRAs fail to accurately predict recorded site response, the site is often considered too complex to be effectively modeled as 1D. While 3D numerical GRAs are possible and believed to be more accurate, there is rarely a 3D subsurface model available for these analyses. The lack of affordable and reliable site characterization methods to quantify spatial variability in subsurface conditions, particularly regarding shear wave velocity (Vs) measurements needed for GRAs, has pushed researchers to adopt stochastic approaches, such as Vs randomization and spatially correlated random fields. However, these stochastically generated models require the assumption of generic, or assumed, input parameters, introducing significant uncertainties into the site response predictions. This paper describes a new geostatistical approach that can be used for building pseudo-3D Vs models as a means to rationally account for spatial variability in GRAs, increase model accuracy, and reduce uncertainty. Importantly, it requires only a single measured Vs profile and a number of simple, cost-effective, horizontal-to-vertical spectral ratio (H/V) noise measurements. Using Gaussian geostatistical regression, irregularly sampled estimates of fundamental site frequency from H/V measurements (f0,H/V) are used to generate a uniform grid of f0,H/V across the site with accompanying Vs profiles that have been scaled to match each f0,H/V value, thereby producing a pseudo-3D Vs model. This approach is demonstrated at the Treasure Island and Delaney Park Downhole Array sites (TIDA and DPDA, respectively). While the pseudo-3D Vs models can be used to incorporate spatial variability into 1D, 2D, or 3D GRAs, their implementation in 1D GRAs at TIDA and DPDA is discussed in a companion paper.

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“…The distinction between the two is less straightforward than in other aspects of ground-motion modeling for several reasons, including the fact that while hazard is calculated at a single point, the motions that will affect the structure being designed will be influenced by the dynamic response of the V S profiles at multiple points across the footprint of the structure’s foundation. Nonetheless, there is a rapidly growing consensus that uncertainty in measured V S profiles is largely epistemic, especially when it reflects differences arising from the use of multiple measurement techniques [such as down-hole, cross-hole, PS logging, and multichannel analysis of surface waves (MASW)] or when it reflects measurement errors within a single measurement technique (Passeri et al, 2019). The state of practice has consequently moved to including alternative V S profiles within a logic-tree formulation in order to explicitly represent the epistemic uncertainty and carry it through to the AFs and the hazard estimates.…”

Section: Aleatory Variability and Epistemic Uncertainty In Site Responsementioning

confidence: 99%

Capturing epistemic uncertainty in site response

Rodríguez-Marek

Bommer

Youngs³

et al. 2020

Earthquake Spectra

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The incorporation of local amplification factors (AFs) determined through site response analyses has become standard practice in site-specific probabilistic seismic hazard analysis (PSHA). Another indispensable feature of the current state of practice in site-specific PSHA is the identification and quantification of all epistemic uncertainties that influence the final hazard estimates. Consequently, logic trees are constructed not only for seismic source characteristics and ground-motion models (GMMs) but also for the site AFs, the latter generally characterized by branches for alternative shear-wave velocity ( VS) profiles. However, in the same way that branch weights on alternative GMMs can give rise to unintentionally narrow distributions of predicted ground-motion amplitudes, the distribution of AFs obtained from a small number of weighted VS profiles will often be quite narrow at some oscillator frequencies. We propose an alternative approach to capturing epistemic uncertainty in site response in order to avoid such unintentionally constricted distributions of AFs using more complete logic trees for site response analyses. Nodes are included for all the factors that influence the calculated AFs, which may include shallow VS profiles, deeper VS profiles, depth of impedance contrasts, low-strain soil damping, and choice of modulus reduction and damping curves. Site response analyses are then executed for all branch combinations to generate a large number of frequency-dependent AFs. Finally, these are re-sampled as a discrete distribution with enough branches to capture the underlying distribution of AFs. While this approach improves the representation of epistemic uncertainty in the dynamic site response characteristics, modeling uncertainty in the AFs is not automatically captured in this way, for which reason it is also proposed that a minimum level of epistemic uncertainty should be imposed on the final distribution.

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Influence of Epistemic Uncertainty in Shear Wave Velocity on Seismic Ground Response Analyses

Cited by 37 publications

References 47 publications

The Polito Surface Wave flat-file Database (PSWD): statistical properties of test results and some inter-method comparisons

The Polito Surface Wave flat-file Database (PSWD): statistical properties of test results and some inter-method comparisons

An H/V Geostatistical Approach for Building Pseudo-3D Vs Models to Account for Spatial Variability in Ground Response Analyses I: Model Development

Capturing epistemic uncertainty in site response

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