Prediction of earthquake ground motion at rock sites in Japan: evaluation of empirical and stochastic approaches for the PEGASOS Refinement Project

Strong ground-motion databases used to develop ground-motion prediction equations (GMPEs) and calibrate stochastic simulation models generally include relatively few recordings on what can be considered as engineering rock or hard rock. Ground-motion predictions for such sites are therefore susceptible to uncertainty and bias, which can then propagate into site-specific hazard and risk estimates. In order to explore this issue we present a study investigating the prediction of ground motion at rock sites in Japan, where a wide range of recording-site types (from soil to very hard rock) are available for analysis. We employ two approaches: empirical GMPEs and stochastic simulations. The study is undertaken in the context of the PEGASOS Refinement Project (PRP), a Senior Seismic Hazard Analysis Committee (SSHAC) Level 4 probabilistic seismic hazard analysis of Swiss nuclear power plants, commissioned by swissnuclear and running from 2008 to 2013. In order to reduce the impact of site-to-site variability and expand the available data set for rock and hard-rock sites we adjusted Japanese ground-motion data (recorded at sites with 110 m s−1 800 m s−1) was found to be comparable (within expected levels of epistemic uncertainty) to predictions using an empirical GMPE, with reduced residual misfit. As expected, due to including site-specific information in the simulations, the reduction in misfit could be isolated to a reduction in the site-related within-event uncertainty. The results of this study support the use of finite or pseudo-finite fault stochastic simulation methods in estimating strong ground motions in regions of weak and moderate seismicity, such as central and northern Europe. Furthermore, it indicates that weak-motion data has the potential to allow estimation of between- and within-site variability in ground motion, which is a critical issue in site-specific seismic hazard analysis, particularly for safety critical structures.ISSN:0956-540XISSN:1365-246

Deriving fragility functions from bilinearized capacity curves for earthquake scenario modelling using the conditional spectrum

The development of fragility curves to perform seismic scenario-based risk assessment requires a fully probabilistic procedure in order to account for uncertainties at each step of the computation. This is especially true when developing fragility curves conditional on an Intensity Measure that is directly available from a ground-motion prediction equation. In this study, we propose a new derivation method that uses realistic spectra instead of design spectral shapes or uniform hazard spectra and allows one to easily account for the features of the site-specific hazard that influences the fragility, without using non-linear dynamic analysis. The proposed method has been applied to typical school building types in the city of Basel (Switzerland) and the results have been compared to the standard practice in Europe. The results confirm that fragility curves are scenario dependent and are particularly sensitive to the magnitude of the earthquake scenario. The same background theory used for the derivation of the fragility curves has allowed an innovative method to be proposed for the conversion of fragility curves to a common IM (i.e. spectral acceleration or PGA). This conversion is the only way direct comparisons of fragility curves can be made and is useful when inter-period correlation cannot be used in scenario loss assessment. Moreover, such conversion is necessary to compare and verify newly developed curves against those from previous studies. Conversion to macroseismic intensity is also relevant for the comparison between mechanical-based and empirical fragility curves, in order to detect possible biases

Gels de poly(octylthiophène) : cristallisation

L'étude de gels conjugués de poly(octylthiophène) par diffraction des rayons X et par calorimétrie différentielle montre que ces réseaux sont semi-cristallins. Etat de cristallinité, propriétés de transport et état d'hétérogénéité à grande échelle semblent être corrélés. La détermination de cette corrélation nécessite une étude approfondie des mécanismes de cristallisation de ces gels polymères dont les premiers résultats sont reportés ici. Ils montrent que taux de cristallinité et vitesses de cristallisation peuvent être déterminés par RMN et, comme attendu, dépendent fortement de l'histoire thermodynamique des gels

A new method for the realistic estimation of seismic ground motion in megacities: the case of Rome

Consiglio Nazionale delle Ricerche (CNR). Biblioteca Centrale / CNR - Consiglio Nazionale delle RichercheSIGLEITItal