GEM Foundation

Pavia, Italy

GEM Foundation

Pavia, Italy
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Brunesi E.,Institute for Advanced Study | Nascimbene R.,European Center for Training and Research in Earthquake Engineering | Pagani M.,GEM Foundation | Beilic D.,Institute for Advanced Study
Journal of Performance of Constructed Facilities | Year: 2015

Field observations following the May 2012 Emilia, Italy, earthquakes have revealed the seismic vulnerability of storage steel tanks typical of the past Italian design practice, highlighting structural deficiencies observed during previous events in other areas and mostly related to lack of structural seismic design and detailing, lack of redundancy, and inadequate anchorage design and execution. Damage was disproportionately high, considering the moderate size of the events (MW=6.11 and MW=5.96 on 20th and 29th May, respectively). Failure modes observed are reported and classified. Comparison is provided with the results of high-definition finite element (FE) dynamic simulations, performed on tanks representative of those inspected. Numerical analyses, accounting for material and geometrical nonlinearities, at the element level, as well as for fluid-structure interaction through highly nonlinear methods, were able to capture the stress/strain concentrations that caused them to collapse. Elephant's foot and diamond buckling induced by hydrodynamic pressures as a result of inertial forces imparted during the earthquakes were reproduced, as well as shear-buckling failure of leg-supported tanks or sliding of unanchored systems. © 2014 American Society of Civil Engineers.

Silva V.,University of Aveiro | Silva V.,GEM Foundation | Crowley H.,GEM Foundation | Varum H.,University of Aveiro | And 2 more authors.
Bulletin of Earthquake Engineering | Year: 2014

The assessment of the seismic risk at a national scale represents an important resource in order to introduce measures that may reduce potential losses due to future earthquakes. This evaluation results from the combination of three components: seismic hazard, structural vulnerability and exposure data. In this study, a review of existing studies focusing on each one of these areas is carried out, and used together with data from the 2011 Building Census in Portugal to compile the required input models for the evaluation of seismic hazard and risk. In order to better characterize the epistemic uncertainty in the calculations, several approaches are considered within a logic tree structure, such as the consideration of different seismic source zonations, the employment of vulnerability functions derived based on various damage criteria and the employment of distinct spatial resolutions in the exposure model. The aim of this paper is thus to provide an overview of the recent developments regarding the different aspects that influence the seismic hazard and risk in Portugal, as well as an up-to-date identification of the regions that are more vulnerable to earthquakes, together with the expected losses for a probability of exceedance of 10 % in 50 years. The results from the present study were obtained through the OpenQuake engine, the open-source software for seismic risk and hazard assessment developed within the global earthquake model (GEM) initiative. © 2014, Springer Science+Business Media Dordrecht.

Monelli D.,GEM Foundation | Pagani M.,GEM Foundation | Weatherill G.,GEM Foundation | Danciu L.,ETH Zurich | Garcia J.,GEM Foundation
Bulletin of the Seismological Society of America | Year: 2014

In any probabilistic seismic-hazard model, the earthquake activity that cannot be associated with well-characterized fault structures is taken into account as seismicity distributed over a geographical region. Ground-motion prediction equations (GMPEs) are generally based on predictor variables describing the spatial extension of a rupture. The approach taken to model rupture finiteness can therefore bias the estimation of seismic hazard. We study the effect of rupture finiteness in modeling distributed seismicity using the OpenQuake (OQ) engine, the open-source software for seismic hazard and risk assessment promoted by the Global Earthquake Model initiative. For a simple test case we show how the inclusion of rupture finiteness, with respect to the point-rupture approximation, leads to a significant increase in the probabilities of exceedance for a given level of motion. We then compare the OQ engine with the calculation software developed by the U.S. Geological Survey-National Seismic Hazard Mapping Project. By considering a gridded seismicity model for California, we show how different approaches for modeling finite ruptures affect seismic- hazard estimates. We show how sensitivity to rupture finiteness depends not only on the spatial distribution of activity rates but also on the GMPE model. Considering two sites in Los Angeles and San Francisco, we show that for a return period of 475 years, the percent difference in the associated ground-motion levels when using point and finite ruptures ranges from 19% to 46%; for a return period of 2475 years the difference ranges from 29% to 58%.

Burton C.G.,GEM Foundation | Silva V.,GEM Foundation
Earthquake Spectra | Year: 2016

At the forefront of the risk assessment sciences is the development of standards, data, and tools for the assessment of earthquake risk. Countries such as Portugal have been targets of extensive earthquake risk assessments to communicate damage potential and to improve methodologies. Few studies, however, have gone beyond the estimation of direct physical impacts by integrating estimates of physical risk (i.e., human or economic losses) with quantified metrics of socioeconomic characteristics of populations. The purpose of this paper is to describe an end-to-end assessment of earthquake risk for mainland Portugal that accounts for physical and social attributes using the Global Earthquake Model's (GEM) suite of risk assessment tools. The results indicate that the potential adverse effects from earthquakes in Portugal are related to interacting conditions, some conditional on geography, some due to the characteristics of the building stock, and some having to do with the social characteristics of populations. © 2016, Earthquake Engineering Research Institute.

Silva V.,GEM Foundation | Crowley H.,GEM Foundation | Pagani M.,GEM Foundation | Monelli D.,ETH Zurich | Pinho R.,GEM Foundation
Natural Hazards | Year: 2014

The Global Earthquake Model aims to combine the main features of state-of-the-art science, global collaboration and buy-in, transparency and openness in an initiative to calculate and communicate earthquake risk worldwide. One of the first steps towards this objective has been the open-source development and release of software for seismic hazard and risk assessment called the OpenQuake engine. This software comprises a set of calculators capable of computing human or economic losses for a collection of assets, caused by a given scenario event, or by considering the probability of all possible events that might happen within a region within a certain time span. This paper provides an insight into the current status of the development of this tool and presents a comprehensive description of each calculator, with example results. © 2013 Springer Science+Business Media Dordrecht.

Ullah S.,Helmholtz Center Potsdam | Bindi D.,Helmholtz Center Potsdam | Pilz M.,Helmholtz Center Potsdam | Danciu L.,ETH Zurich | And 6 more authors.
Annals of Geophysics | Year: 2015

Central Asia is one of the seismically most active regions in the world. Its complex seismicity due to the dcollision of the Eurasian and Indian plates has resulted in some of the world’s largest intra-plate events over history. The region is dominated by reverse faulting over strike slip and normal faulting events. The GSHAP project (1999), aiming at a hazard assessment on a global scale, indicated that the region of Central Asia is characterized by peak ground accelerations for 10% probability of exceedance in 50 years as high as 9 m/s2. In this study, carried out within the framework of the EMCA project (Earthquake Model Central Asia), the area source model and different kernel approaches are used for a probabilistic seismic hazard assessment (PSHA) for Central Asia. The seismic hazard is assessed considering shallow (depth < 50 km) seismicity only and employs an updated (with respect to previous projects) earthquake catalog for the region. The seismic hazard is calculated in terms of macroseismic intensity (MSK-64), intended to be used for the seismic risk maps of the region. The hazard maps, shown in terms of 10% probability of exceedance in 50 years, are derived by using the OpenQuake software [Pagani et al. 2014], which is an open source software tool developed by the GEM (Global Earthquake Model) foundation. The maximum hazard observed in the region reaches an intensity of around 8 in southern Tien Shan for 475 years mean return period. The maximum hazard estimated for some of the cities in the region, Bishkek, Dushanbe, Tashkent and Almaty, is between 7 and 8 (7-8), 8.0, 7.0 and 8.0 macroseismic Intensity, respectively, for 475 years mean return period, using different approaches. The results of different methods for assessing the level of seismic hazard are compared and their underlying methodologies are discussed. © 2015 by the Istituto Nazionale di Geofisica e Vulcanologia. All rights reserved.

How communities respond to and recover from damaging hazard events could be contextualized in terms of their disaster resilience. Although numerous efforts have sought to explain the determinants of disaster resilience, the ability to measure the concept is increasingly being seen as a key step toward disaster risk reduction. The development of standards that are meaningful for measuring resilience remains a challenge, however. This is partially because there are few explicit sets of procedures within the literature that outline how to measure and compare communities in terms of their resilience. The primary purpose of this article is to advance the understanding of the multidimensional nature of disaster resilience and to provide an externally validated set of metrics for measuring resilience at subcounty levels of geography. A set of metrics covering social, economic, institutional, infrastructural, community-based, and environmental dimensions of resilience was identified, and the validity of the metrics is addressed via real-world application using Hurricane Katrina and the recovery of the Mississippi Gulf Coast in the United States as a case study. © 2015, © 2015 by Association of American Geographers.

Burton C.G.,GEM Foundation | Khazai B.,Center for Disaster Management and Risk Reduction Technology | Silva V.,GEM Foundation
NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering | Year: 2014

At the core of the Global Earthquake Model (GEM) is the development of state-of-the-art modeling capabilities that can be used worldwide for the assessment and communication of seismic risk. While many approaches for understanding seismic risk exist, it is the dynamic interrelationships between hazard potential, physical risk, and the social conditions of populations that are becoming the focal point for policy-makers, emergency managers, stakeholders, and the general public. The purpose of this paper is to introduce GEM's Integrated Risk Modeling Toolkit, an open-source software tool that will allow risk analysts to draw from results on exposure, predicted mortality, and property loss, and combine these results with socio-economic data and/or computed models of social and economic vulnerability in a robust and meaningful way. A proof of concept using Portugal is demonstrated to assess the total (seismic) risk of that country.

Silva V.,University of Aveiro | Silva V.,GEM Foundation | Crowley H.,GEM Foundation | Varum H.,University of Aveiro | And 4 more authors.
Bulletin of Earthquake Engineering | Year: 2015

A vulnerability model capable of providing the probabilistic distribution of loss ratio for a set of intensity measure levels is a fundamental tool to perform earthquake loss estimation and seismic risk assessment. The aim of the study presented herein is to develop a set of vulnerability functions for 48 reinforced concrete building typologies, categorized based on the date of construction (which has a direct relation with the design code level), number of storeys (height of the building) and seismic zonation (which affects the design of the buildings). An analytical methodology was adopted, in which thousands of nonlinear dynamic analyses were performed on 2D moment resisting frames with masonry infills, using one hundred ground motion records that are compatible, to the extent possible, with the Portuguese tectonic environment. The generation of the structural models was carried out using the probabilistic distribution of a set of geometric and material properties, compiled based on information gathered from a large sample of drawings and technical specifications of typical Portuguese reinforced concrete buildings, located in various regions in the country. Various key aspects in the development of the vulnerability model are investigated herein, such as the selection of the ground motion records, the modelling of the infilled frames, the definition of the damage criterion and the evaluation of dynamic (i.e. period of vibration) and structural (i.e. displacement and base shear capacity) parameters of the frames. A statistical bootstrap method is demonstrated to estimate the variability of the loss ratio at each intensity measure level, allowing the estimation of the mean, as well as 10 and 90 % percentile vulnerability curves. © 2014, Springer Science+Business Media Dordrecht.

Bal I.E.,EUCENTRE | Bommer J.J.,Imperial College London | Stafford P.J.,Imperial College London | Crowley H.,GEM Foundation | Pinho R.,GEM Foundation
Earthquake Spectra | Year: 2010

Exposure data available to developers of earthquake loss models are often very crudely aggregated spatially, and in such cases very considerable effort can be required to refine the geographical resolution of the building stock inventory. The influence of the geographical resolution of the exposure data for the Sea of Marmara region in Turkey is explored using several different levels of spatial aggregation to estimate the losses due to a single earthquake scenario. The results show that the total damage over an urban area, expressed as a mean damage ratio (MDR), is rather insensitive to the spatial resolution of the exposure data if a sufficiently large number of ground-motion simulations are used. However, the variability of the MDR estimates does reduce as the spatial resolution becomes higher, reducing the number of simulations required, although there appears to be a law of diminishing returns in going to very high exposure data resolution. This is largely due to the inherent and irreducible spatial variability of ground motion, which suggests that if only mean MDR estimates are needed, the effort required to refine the spatial definition of exposure data is not justified. © 2010, Earthquake Engineering Research Institute.

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