ALBERT

Description: This paper presents an integrated approach to conduct a scenario-based volcanic risk assessment on a variety of exposed assets, such as residential buildings, cultivated areas, network infrastructures or individual strategic buildings. The focus is put on the simulation of scenarios, based on deterministic adverse event input, which are applied to the case study of an effusive eruption on the Mount Cameroon volcano, resulting in the damage estimation of the assets located in the area. The work is based on the recent advances in the field of seismic risk. A software for systemic risk scenario analysis developed within the FP7 project SYNER-G has been adapted to address the issue of volcanic risk. Most significant improvements include the addition of vulnerability models adapted to each kind of exposed element and the possibility to quantify the successive potential damages inflicted by a sequence of adverse events (e.g. lava flows, tephra fall, etc.). The use of an object-oriented architecture gives the opportunity to model and compute the physical damage of very disparate types of infrastructures under the same framework. Finally, while the risk scenario approach is limited to the assessment of the physical impact of adverse events, a specific focus on strategic infrastructures and a dialogue with stakeholders helps in evaluating the potential wider indirect consequences of an eruption.

Description: This paper presents an integrated approach to conduct a scenario-based volcanic risk assessment on a variety of exposed assets, such as residential buildings, cultivated areas, network infrastructures or individual strategic buildings. The focus is put on the simulation of scenarios, based on deterministic adverse events input, which are applied to the case-study of an effusive eruption on the Mount Cameroon volcano, resulting in the damage estimation of the assets located in the area. The work is based on the recent advances in the field of seismic risk. A software for systemic risk scenario analysis developed within the FP7 project SYNER-G has been adapted to address the issue of volcanic risk. Most significant improvements include the addition of vulnerability models adapted to each kind of exposed element and the possibility to quantify the successive potential damages inflicted by a sequence of adverse events (e.g. lava flows, tephra fall, etc.). The use of an object-oriented architecture gives the opportunity to model and compute the physical damage of very disparate types of infrastructures under the same framework. Finally, while the risk scenario approach is limited to the assessment of the physical impact of adverse events, a specific focus on strategic infrastructures and a dialogue with stakeholders helps in evaluating the potential wider indirect consequences of an eruption.

Description: This article proposes a new framework for the inclusion of site effects in empirical ground-motion prediction equations (GMPEs) by characterizing stations through their one-quarter wavelength velocities and assessed confidence limits. The approach is demonstrated for 14 stations of the French accelerometric network (Reseau Accelerometrique Permanent). This method can make use of all the available information about a given site, for example, the surface geology, the soil profile, standard penetration test measurements, near-surface velocity estimated from the topographic slope, depth to bedrock, and crustal structure. These data help to constrain the velocity profile down to a few kilometers. Based on a statistical study of 858 real profiles from three different regions (Japan, western North America, and France) physically realistic profiles are generated that comply with the information available for each site. In order to evaluate the confidence limits for the shear-wave velocity profiles and derived site amplifications for each station, a stochastic method is adopted: several thousand profiles are randomly generated based on parameters derived in the statistical study and the constraints available for each station. Then, the one-quarter wavelength assumption is used to estimate the amplification for each station. It is found that a good knowledge of near-surface attenuation (i.e., kappa or Q) is mandatory for obtaining precise amplification estimates at high frequencies. Nevertheless, the proposed scheme highlights the important differences in the uncertainties of the site amplifications, depending on the information available for a given station. We suggest that these results could, therefore, be used when developing GMPEs by weighting records from each station depending on the variability in the computed one-quarter wavelength velocities. This approach relies on the assumption that local site effects are only one-dimensional, which is far from true, especially in sedimentary basins. However, most GMPEs only model one-dimensional site effects, so this is not an issue specific to this study. Finally, a way to improve this technique is to use earthquakes or noise recorded at the stations to further constrain the shear-wave velocity profiles and to consequently derive more accurate one-quarter wavelength velocities.

Description: Fragility curves are generally developed using a single parameter to relate the level of shaking to the expected structural damage. The main goal of this work is to use several parameters to characterize the earthquake ground motion. The fragility curves will, therefore, become surfaces when the ground motion is represented by two parameters. To this end, the roles of various strong-motion parameters on the induced damage in the structure are compared through nonlinear time-history numerical calculations. A robust structural model that can be used to perform numerous nonlinear dynamic calculations, with an acceptable cost, is adopted. The developed model is based on the use of structural elements with concentrated nonlinear damage mechanics and plasticity-type behavior. The relations between numerous ground-motion parameters, characterizing different aspects of the shaking, and the computed damage are analyzed and discussed. Natural and synthetic accelerograms were chosen/computed based on a consideration of the magnitude-distance ranges of design earthquakes. A complete methodology for building fragility surfaces based on the damage calculation through nonlinear numerical analysis of multi-degree-of-freedom systems is proposed. The fragility surfaces are built to represent the probability that a given damage level is reached (or exceeded) for any given level of ground motion characterized by the two chosen parameters. The results show that an increase from one to two ground-motion parameters leads to a significant reduction in the scatter in the fragility analysis and allows the uncertainties related to the effect of the second ground-motion parameter to be accounted for within risk assessments. Copyright © 2009 John Wiley & Sons, Ltd.

Description: Current ground-motion prediction equations invariably assume that site conditions at strong-motion stations, often characterized by the average shear-wave velocity to a depth of 30 m (V (sub S30) ), are known to a uniform accuracy. This is, however, rarely the case. In this article, we present a regression procedure based on generalized least-squares and maximum-likelihood approaches that take into account the varying uncertainties on V (sub S30) . Assuming that V (sub S30) s for various groups of stations are known to different accuracies, application of this procedure to a large set of records from the Japanese KiK-net shows that the regression coefficients are largely insensitive to the assumption of nonuniform uncertainties. However, this procedure allows the computation of a site-specific standard deviation (sigma ) that should be used for sites where V (sub S30) is known to different accuracies (e.g., a site only specified by class or a site with a measured V (sub S) profile). For sites with a measured V (sub S) profile, this leads to lower site-specific sigma than for a site that is poorly characterized because this technique explicitly models the separation between the epistemic uncertainty in V (sub S30) and the aleatory variability in predicted ground motion.

Description: This Scientific Technical Report presents two so-called “Reference reports” produced during the MATRIX project. These reports were provided to the European Commission asdeliverables, namely D8.4 “MATRIX Results I and Reference Report” and D8.5 “MATRIX Results II and Reference Report”. D8.4 presented a series of specific reports outlining theresults of the project, written in a manner accessible not only to the specialist but with a broader audience in mind. D8.5 deals with the risk governance within a multi-hazard and risk context and has since been published. We therefore divide with document in two, where part1 represented the outcomes presented in D8.4 while D8.5 forms part 2.