A Probabilistic Method for the Prediction of Earthquake-Induced Slope Displacements

This work presents a probabilistic method for estimating earthquake-induced nonlinear slope displacements. This method is applicable to any kind of slope, embankment and earth/rockfill dam. When coupled with Probabilistic Seismic Hazard Analysis at the slope site, it produces estimates of the annual probability that a permanent deformation of the slope will be exceeded. The proposed method uses a set of 2D numerical analyses with non-linear constitutive relationships for the soil formations to establish a probabilistic relationship between one or more ground motion parameters and the permanent displacement at a specific location within the slope. The analyses, which are performed using the computer code FLAC 5.0 (Itasca, 2005), use as input a set of different recorded accelerograms that include both horizontal and vertical components. The method is applied to the Salcito landslide (Molise, Southern Italy), which was investigated in detail by Bozzano et al. (2008). The stability of the same slope is also assessed using the conventional Newmark’s method and a decoupled approach and the results are compared and contrasted with those obtained using FLAC

Issues in Harmonization of Seismic Performance via Risk Targeted Spectra

Current seismic design code provisions are mainly based on checking structural performance at a single seismic intensity associated with a pre-defined return period. For instance, in EN1998, a ground motion with 10% probability of exceedance in 50 years is used for design. This design procedure, with the inclusion of partial safety factors, is assumed to provide sufficient safety margin against earthquakes for newly designed buildings. Nevertheless, it does not specifically determine the expected seismic risk related to any performance level or limit state. Therefore, it may result in non-uniform risk for buildings located in different sites within a region (or country), even for places with identical design intensities. Instead, ASCE 7-10 incorporates Risk Targeted design maps that suggest the application of suitable spectra adjustment factors, in order to ensure a reasonably low uniform collapse risk. Making use of simplified single degree of freedom structures defined in several configurations of period and ductility, our aim is to test the effectiveness of the adjustment factors computed under different assumptions. It is shown that, although matching is not practically possible, harmonization remains a viable target, offering insights for possible future adoption of Risk Targeted Spectra in forthcoming seismic codes.The second author acknowledges the support of the European Commission via the Horizon 2020 Grant No. 769129 PANOPTIS: Development of a Decision Support System for increasing the Resilience of Transportation Infrastructure based on combined use of terrestrial and airborne sensors and advanced modelling tools

Impact of partially non-ergodic site-specific probabilistic seismic hazard on risk assessment of single buildings

International audienceThe growth of global ground-motion databases has allowed generation of non-ergodic ground-motion prediction equations (GMPEs) based on specific on-site recordings. Several studies have investigated the differences between the hazard estimates from ergodic versus non-ergodic GMPEs. Here instead we focus on the impact of non-ergodic PSHA estimates on the seismic risk of nonlinear single-degree-of-freedom systems representing ductile structures and compare it with the traditional risk estimates obtained using ergodic GMPEs. The structure-and-site-specific risk estimates depend not only on the difference in the hazard estimates but also on the different hazard-consistent ground-motion record selection that informs the response calculation. The more accurate structure-and-site-specific non-ergodic risk estimates show that traditional ones may be biased in a way impossible to predict a priori. Hence, the use of the non-ergodic approach is recommended, whenever possible. However, further advancements of non-ergodic GMPEs are necessary before being routinely utilized in real-life risk assessment applications

Spectral Matching in Time Domain: A Seismological and Engineering Analysis

International audienc

Disaggregation of Probabilistic Ground-Motion Hazard in Italy

Probabilistic seismic hazard analysis is a process that integrates over aleatory uncertainties (e.g., future earthquake locations and magnitudes) to calculate the mean annual rate of exceedance (MRE) of given ground-motion parameter values at a site. These rates reflect the contributions of all the sources whose seismic activity is deemed to affect the hazard at that site. Seismic hazard disaggregation provides insights into the earthquake scenarios driving the hazard at a given ground-motion level. This work presents the disaggregation at each grid point of the Italian rock ground-motion hazard maps developed by Gruppo di Lavoro MPS (2004), Meletti and Montaldo (2007), and Montaldo and Meletti (2007). Disaggregation is used here to compute the contributions to the MRE of peak ground horizontal acceleration (PGA) and 5%-damped 0.2, 1.0, and 2.0 sec spectral acceleration values corresponding to different mean return periods (MRPs of 475 and 2475 yr) from different scenarios. These sce- narios are characterized by bins of magnitude, M, source-to-site distance, R, and number, \u3b5, of standard deviations that the ground-motion parameter is away from its median value for that M R pair as estimated by a prediction equation. Maps showing the geographical distribution of the mean and modal values of M, R, and \u3b5 are presented for the first time for all of Italy. Complete joint M\u2013R\u2013\u3b5 distributions are also presented for selected cities. Except for sites where the earthquake activity is characterized by sporadic low-magnitude events, the hazard is generally dominated by local seismicity. Moreover, as expected, the MRE of long-period spectral accelerations is generally con- trolled by large magnitude earthquakes at long distances while smaller events at shorter distances dominate the PGA and short-period spectral acceleration hazard. Finally, for a given site, as the MRP increases the dominant earthquakes tend to become larger and to occur closer to the site investigated

Advances on risk-targeted hazard estimation within the European context

The design of new structures according to modern seismic regulations requires the definition of a ground motion for a given return period, for which the structure is designed. The implicit assumption is that the resulting annual collapse probability is equally uniform for all structures, regardless of their structural properties or location. However, the uncertainty in the collapse capacity and discrepancies in the slope of the seismic hazard curves at different sites lead to a level of risk that is site- and structure-specific, and thus not uniform for all structures across a region. The estimation of risk-targeted hazard maps allows for the definition of a design ground motion that would lead to a nominal uniform level of risk nationally, compliant with a transparent and pre-specified risk threshold. In this paper, the seismic hazard results recently released under the FP7 European project SHARE are employed to compute risk-targeted hazard maps for Europe, according to a fixed annual probability of collapse that is in agreement with current levels of safety. The preliminary results shown here expose large areas of Europe where the design ground motion could be significantly lowered without compromising the current level of accepted risk.Non UBCUnreviewedThis collection contains the proceedings of ICASP12, the 12th International Conference on Applications of Statistics and Probability in Civil Engineering held in Vancouver, Canada on July 12-15, 2015. Abstracts were peer-reviewed and authors of accepted abstracts were invited to submit full papers. Also full papers were peer reviewed. The editor for this collection is Professor Terje Haukaas, Department of Civil Engineering, UBC Vancouver.FacultyResearche

Consequence Functions for Seismic Risk Assessment: A review of consequence modelling state-of-practice for ERM-CH – Module D

The report looks into the state-of-the-art in consequence modelling for the different loss categories, reviews the existing methodologies for deriving them, and discusses their implications on risk estimates from social, insurance, engineering, and catastrophe modelers’ perspectives. As such, the report first provide background on the vulnerability analysis stage because its subcomponents (including consequence modelling) cannot be scrutinized independently. Afterwards, the state-of-the-art in consequence modelling is examined

Sensitivity Analysis of Parameters for Probabilistic Seiosmic Hazard Assessment of Western Liguria (North-Western Italy)

The use of logic trees in probabilistic seismic hazard analyses often involves a large number of branches that reflect the uncertainty in the selection of different models and in the selection of the parameter values of each model. The sensitivity analysis, as proposed by Rabinowitz and Steinberg [Rabinowitz, N., Steinberg, D.M., 1991. Seismic hazard sensitivity analysis: a multi- parameter approach. Bull. Seismol. Soc. Am. 81, 796–817], is an efficient tool that allows the construction of logic trees focusing attention on the parameters that have greater impact on the hazard. In this paper the sensitivity analysis is performed in order to identify the parameters that have the largest influence on the Western Liguria (North Western Italy) seismic hazard. The analysis is conducted for six strategic sites following the multi- parameter approach developed by Rabinowitz and Steinberg [Rabinowitz, N., Steinberg, D.M., 1991. Seismic hazard sensitivity analysis: a multi-parameter approach. Bull. Seismol. Soc. Am. 81, 796–817] and accounts for both mean hazard values and hazard values corresponding to different percentiles (e.g., 16%-ile and 84%-ile). The results are assessed in terms of the expected PGA with a 10% probability of exceedance in 50 years for rock conditions and account for both the contribution from specific source zones using the Cornell approach [Cornell, C.A., 1968. Engineering seismic risk analysis. Bull. Seismol. Soc. Am. 58, 1583–1606] and the spatially smoothed seismicity [Frankel, A., 1995. Mapping seismic hazard in the Central and Eastern United States. Seismol. Res. Lett. 66, 8–21]. The influence of different procedures for calculating seismic hazard, seismic catalogues (epicentral parameters), source zone models, frequency–magnitude parameters, maximum earthquake magnitude values and attenuation relationships is considered. As a result, the sensitivity analysis allows us to identify the parameters with higher influence on the hazard. Only these parameters should be subjected to careful discussion or further research in order to reduce the uncertainty in the hazard while those with little or no effect can be excluded from subsequent logic-tree-based seismic hazard analyses