TY - JOUR A1 - Delavaud, Elise A1 - Cotton, Fabrice Pierre A1 - Akkar, Sinan A1 - Scherbaum, Frank A1 - Danciu, Laurentiu A1 - Beauval, Celine A1 - Drouet, Stephane A1 - Douglas, John A1 - Basili, Roberto A1 - Sandikkaya, M. Abdullah A1 - Segou, Margaret A1 - Faccioli, Ezio A1 - Theodoulidis, Nikos T1 - Toward a ground-motion logic tree for probabilistic seismic hazard assessment in Europe JF - Journal of seismology N2 - The Seismic Hazard Harmonization in Europe (SHARE) project, which began in June 2009, aims at establishing new standards for probabilistic seismic hazard assessment in the Euro-Mediterranean region. In this context, a logic tree for ground-motion prediction in Europe has been constructed. Ground-motion prediction equations (GMPEs) and weights have been determined so that the logic tree captures epistemic uncertainty in ground-motion prediction for six different tectonic regimes in Europe. Here we present the strategy that we adopted to build such a logic tree. This strategy has the particularity of combining two complementary and independent approaches: expert judgment and data testing. A set of six experts was asked to weight pre-selected GMPEs while the ability of these GMPEs to predict available data was evaluated with the method of Scherbaum et al. (Bull Seismol Soc Am 99:3234-3247, 2009). Results of both approaches were taken into account to commonly select the smallest set of GMPEs to capture the uncertainty in ground-motion prediction in Europe. For stable continental regions, two models, both from eastern North America, have been selected for shields, and three GMPEs from active shallow crustal regions have been added for continental crust. For subduction zones, four models, all non-European, have been chosen. Finally, for active shallow crustal regions, we selected four models, each of them from a different host region but only two of them were kept for long periods. In most cases, a common agreement has been also reached for the weights. In case of divergence, a sensitivity analysis of the weights on the seismic hazard has been conducted, showing that once the GMPEs have been selected, the associated set of weights has a smaller influence on the hazard. KW - Logic trees KW - Ground-motion prediction equations KW - Expert judgment KW - Model selection KW - Seismic hazard assessment Y1 - 2012 U6 - https://doi.org/10.1007/s10950-012-9281-z SN - 1383-4649 VL - 16 IS - 3 SP - 451 EP - 473 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Beauval, Celine A1 - Hainzl, Sebastian A1 - Scherbaum, Frank T1 - The impact of the spatial uniform distribution of seismicity on probabilistic seismic-hazard estimation JF - Bulletin of the Seismological Society of America N2 - The first step in the estimation of probabilistic seismic hazard in a region commonly consists of the definition and characterization of the relevant seismic sources. Because in low-seismicity regions seismicity is often rather diffuse and faults are difficult to identify, large areal source zones are mostly used. The corresponding hypothesis is that seismicity is uniformly distributed inside each areal seismic source zone. In this study, the impact of this hypothesis on the probabilistic hazard estimation is quantified through the generation of synthetic spatial seismicity distributions. Fractal seismicity distributions are generated inside a given source zone and probabilistic hazard is computed for a set of sites located inside this zone. In our study, the impact of the spatial seismicity distribution is defined as the deviation from the hazard value obtained for a spatially uniform seismicity distribution. From the generation of a large number of synthetic distributions, the correlation between the fractal dimension D and the impact is derived. The results show that the assumption of spatially uniform seismicity tends to bias the hazard to higher values. The correlation can be used to determine the systematic biases and uncertainties for hazard estimations in real cases, where the fractal dimension has been determined. We apply the technique in Germany (Cologne area) and in France (Alps). Y1 - 2006 U6 - https://doi.org/10.1785/0120060073 SN - 0037-1106 VL - 96 IS - 6 SP - 2465 EP - 2471 PB - GeoScienceWorld CY - Alexandria, Va. ER - TY - JOUR A1 - Beauval, Celine A1 - Tasan, Hilal A1 - Laurendeau, Aurore A1 - Delavaud, Elise A1 - Cotton, Fabrice Pierre A1 - Gueguen, Philippe A1 - Kühn, Nicolas T1 - On the testing of ground-motion prediction equations against small-magnitude data JF - Bulletin of the Seismological Society of America N2 - Ground-motion prediction equations (GMPE) are essential in probabilistic seismic hazard studies for estimating the ground motions generated by the seismic sources. In low-seismicity regions, only weak motions are available during the lifetime of accelerometric networks, and the equations selected for the probabilistic studies are usually models established from foreign data. Although most GMPEs have been developed for magnitudes 5 and above, the minimum magnitude often used in probabilistic studies in low-seismicity regions is smaller. Disaggregations have shown that, at return periods of engineering interest, magnitudes less than 5 may be contributing to the hazard. This paper presents the testing of several GMPEs selected in current international and national probabilistic projects against weak motions recorded in France (191 recordings with source-site distances up to 300 km, 3:8 <= M-w <= 4:5). The method is based on the log-likelihood value proposed by Scherbaum et al. (2009). The best-fitting models (approximately 2:5 <= LLH <= 3:5) over the whole frequency range are the Cauzzi and Faccioli (2008), Akkar and Bommer (2010), and Abrahamson and Silva (2008) models. No significant regional variation of ground motions is highlighted, and the magnitude scaling could be the predominant factor in the control of ground-motion amplitudes. Furthermore, we take advantage of a rich Japanese dataset to run tests on randomly selected low-magnitude subsets, and confirm that a dataset of similar to 190 observations, the same size as the French dataset, is large enough to obtain stable LLH estimates. Additionally we perform the tests against larger magnitudes (5-7) from the Japanese dataset. The ranking of models is partially modified, indicating a magnitude scaling effect for some of the models, and showing that extrapolating testing results obtained from low-magnitude ranges to higher magnitude ranges is not straightforward. Y1 - 2012 U6 - https://doi.org/10.1785/0120110271 SN - 0037-1106 VL - 102 IS - 5 SP - 1994 EP - 2007 PB - Seismological Society of America CY - El Cerrito ER - TY - JOUR A1 - Yepes, Hugo A1 - Audin, Laurence A1 - Alvarado, Alexandra A1 - Beauval, Celine A1 - Aguilar, Jorge A1 - Font, Yvonne A1 - Cotton, Fabrice Pierre T1 - A new view for the geodynamics of Ecuador: Implication in seismogenic source definition and seismic hazard assessment JF - Tectonics N2 - A new view of Ecuador's complex geodynamics has been developed in the course of modeling seismic source zones for probabilistic seismic hazard analysis. This study focuses on two aspects of the plates' interaction at a continental scale: (a) age-related differences in rheology between Farallon and Nazca plates—marked by the Grijalva rifted margin and its inland projection—as they subduct underneath central Ecuador, and (b) the rapidly changing convergence obliquity resulting from the convex shape of the South American northwestern continental margin. Both conditions satisfactorily explain several characteristics of the observed seismicity and of the interseismic coupling. Intermediate-depth seismicity reveals a severe flexure in the Farallon slab as it dips and contorts at depth, originating the El Puyo seismic cluster. The two slabs position and geometry below continental Ecuador also correlate with surface expressions observable in the local and regional geology and tectonics. The interseismic coupling is weak and shallow south of the Grijalva rifted margin and increases northward, with a heterogeneous pattern locally associated to the Carnegie ridge subduction. High convergence obliquity is responsible for the North Andean Block northeastward movement along localized fault systems. The Cosanga and Pallatanga fault segments of the North Andean Block-South American boundary concentrate most of the seismic moment release in continental Ecuador. Other inner block faults located along the western border of the inter-Andean Depression also show a high rate of moderate-size earthquake production. Finally, a total of 19 seismic source zones were modeled in accordance with the proposed geodynamic and neotectonic scheme. Y1 - 2016 U6 - https://doi.org/10.1002/2015TC003941 SN - 0278-7407 SN - 1944-9194 VL - 35 SP - 1249 EP - 1279 PB - American Geophysical Union CY - Washington ER -