107 research outputs found

    Selection of ground motion prediction equations for the global earthquake model

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    Ground motion prediction equations (GMPEs) relate ground motion intensity measures to variables describing earthquake source, path, and site effects. From many available GMPEs, we select those models recommended for use in seismic hazard assessments in the Global Earthquake Model. We present a GMPE selection procedure that evaluates multidimensional ground motion trends (e.g., with respect to magnitude, distance, and structural period), examines functional forms, and evaluates published quantitative tests of GMPE performance against independent data. Our recommendations include: four models, based principally on simulations, for stable continental regions; three empirical models for interface and in-slab subduction zone events; and three empirical models for active shallow crustal regions. To approximately incorporate epistemic uncertainties, the selection process accounts for alternate representations of key GMPE attributes, such as the rate of distance attenuation, which are defensible from available data. Recommended models for each domain will change over time as additional GMPEs are developed

    Reduced Cortisol and Metabolic Responses of Thin Ewes to an Acute Cold Challenge in Mid-Pregnancy: Implications for Animal Physiology and Welfare

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    Background: Low food availability leading to reductions in Body Condition Score (BCS; 0 indicates emaciation and 5 obesity) in sheep often coincides with low temperatures associated with the onset of winter in New Zealand. The ability to adapt to reductions in environmental temperature may be impaired in animals with low BCS, in particular during pregnancy when metabolic demand is higher. Here we assess whether BCS affects a pregnant animal’s ability to cope with cold challenges. Methods: Eighteen pregnant ewes with a BCS of 2.760.1 were fed to attain low (LBC: BCS2.360.1), medium (MBC: BCS3.260.2) or high BCS (HBC: BCS3.660.2). Shorn ewes were exposed to a 6-h acute cold challenge in a climate-controlled room (wet and windy conditions, 4.460.1uC) in mid-pregnancy. Blood samples were collected during the BCS change phase, acute cold challenge and recovery phase. Results: During the BCS change phase, plasma glucose and leptin concentrations declined while free fatty acids (FFA) increased in LBC compared to MBC (P,0.01, P,0.01 and P,0.05, respectively) and HBC ewes (P,0.05, P,0.01 and P,0.01, respectively). During the cold challenge, plasma cortisol concentrations were lower in LBC than MBC (P,0.05) and HBC ewes (P,0.05), and FFA and insulin concentrations were lower in LBC than HBC ewes (P,0.05 and P,0.001, respectively). Leptin concentrations declined in MBC and HBC ewes while remaining unchanged in LBC ewes (P,0.01). Glucose concentrations and internal body temperature (Tcore) increased in all treatments, although peak Tcore tended to be higher in HBC ewes (P,0.1). During the recovery phase, T4 concentrations were lower in LBC ewes (P,0.05). Conclusion: Even though all ewes were able to increase Tcore and mobilize glucose, low BCS animals had considerably reduced cortisol and metabolic responses to a cold challenge in mid-pregnancy, suggesting that their ability to adapt to cold challenges through some of the expected pathways was reduced

    Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

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    Capturing geographically-varying uncertainty in earthquake ground motion models or what we think we know may change

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    Our knowledge of earthquake ground motions of engineering significance varies geographically. The prediction of earthquake shaking in parts of the globe with high seismicity and a long history of observations from dense strong-motion networks, such as coastal California, much of Japan and central Italy, should be associated with lower uncertainty than ground-motion models for use in much of the rest of the world, where moderate and large earthquakes occur infrequently and monitoring networks are sparse or only recently installed. This variation in uncertainty, however, is not often captured in the models currently used for seismic hazard assessments, particularly for national or continental-scale studies. In this theme lecture, firstly I review recent proposals for developing ground-motion logic trees and then I develop and test a new approach for application in Europe. The proposed procedure is based on the backbone approach with scale factors that are derived to account for potential differences between regions. Weights are proposed for each of the logic-tree branches to model large epistemic uncertainty in the absence of local data. When local data are available these weights are updated so that the epistemic uncertainty captured by the logic tree reduces. I argue that this approach is more defensible than a logic tree populated by previously published ground-motion models. It should lead to more stable and robust seismic hazard assessments that capture our doubt over future earthquake shaking

    Interaction between surface waves and absorbing boundaries for wave propagation in geological basins: 2D numerical simulations

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    International audienceSurface waves control the peak of the seismic records at regional and teleseismic distances. In complex structures, such as basins, their amplitude is produced by the interference between the topography and the wedges of the model. Therefore, they represent a challenging target for numerical simulations. When modelling low frequencies in thin media, such as basins and waveguides, some instabilities arise from the interaction between propagating evanescent waves and the artificial layer, required to avoid spurious reflection to be sent back into the elastic volume. Here we propose to generalize the absorbing boundary conditions, by adding a cut-off frequency and an overdamping. The efficiency is demonstrated through a comparison with analytical solutions. Finally an analysis is performed by adopting a complex basin geometry, where we show that the pollution of classical absorbing conditions becomes significant near the edges of the model
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