Tiziana Rossetto

Derivation of vulnerability functions for European-type RC structures based on observational data

Abstract In this paper existing vulnerability relationships for reinforced concrete structures are reviewed with a view to their application to a European (and similar) seismic risk assessment scenario. New empirical fragility curves for reinforced concrete building populations are derived based on a data bank of 99 post-earthquake damage distributions observed in 19 earthquakes and concerning a total of 340 000 RC structures. The heterogeneous observational data are reinterpreted in terms of a new damage scale: homogenised reinforced concrete (HRC-scale), which is calibrated experimentally and allows a distinction to be made between the seismic resistances of different structural systems. The feasibility of using observation-based data for the generation of vulnerability curves for different strong ground motion parameters is investigated. The notion of developing a set of ‘homogeneous’ vulnerability relationships, applicable to different lateral-load resisting systems is explored and a series of relationships for different building height and age-classes are proposed. Large uncertainties are associated with the empirical relationships due to the nature and scarcity of observational data. The role of combined observation-testing-analysis as the basis for deriving reliable vulnerability formulations is thus emphasised. Notwithstanding, the statistics of the new vulnerability functions are a significant improvement over existing observation-based curves for European RC structures.

Empirical fragility assessment of buildings affected by the 2011 Great East Japan tsunami using improved statistical models

Tsunamis are destructive natural phenomena which cause extensive damage to the built environment, affecting the livelihoods and economy of the impacted nations. This has been demonstrated by the tragic events of the Indian Ocean tsunami in 2004, or the Great East Japan tsunami in 2011. Following such events, a few studies have attempted to assess the fragility of the existing building inventory by constructing empirical stochastic functions, which relate the damage to a measure of tsunami intensity. However, these studies typically fit a linear statistical model to the available damage data, which are aggregated in bins of similar levels of tsunami intensity. This procedure, however, cannot deal well with aggregated data, low and high damage probabilities, nor does it result in the most realistic representation of the tsunami-induced damage. Deviating from this trend, the present study adopts the more realistic generalised linear models which address the aforementioned disadvantages. The proposed models are fitted to the damage database, containing 178,448 buildings surveyed in the aftermath of the 2011 Japanese tsunami, provided by the Ministry of Land, Infrastructure Transport and Tourism in Japan. In line with the results obtained in previous studies, the fragility curves show that wooden buildings (the dominant construction type in Japan) are the least resistant against tsunami loading. The diagnostics show that taking into account both the building’s construction type and the tsunami flow depth is crucial to the quality of the damage estimation and that these two variables do not act independently. In addition, the diagnostics reveal that tsunami flow depth estimates low levels of damage reasonably well; however, it is not the most representative measure of intensity of the tsunami for high damage states (especially structural damage). Further research using disaggregated damage data and additional explanatory variables is required in order to obtain reliable model estimations of building damage probability.

Social Representations of Earthquakes: A Study of People Living in Three Highly Seismic Areas

Much research on peoples seismic adjustment activity in highly seismic areas has assumed that low levels of adjustment are attributable to insufficient awareness of seismic risk. Empirical evidence for this assumption is weak, and there is growing appreciation of the role played by sociocultural and emotional variables in risk perception and behavior. This study explored these socio-cultural and emotional dimensions via 144 interviews and questionnaires, with matched samples of locals in Seattle (United States), Osaka (Japan), and Izmir (Turkey). The data showed that high awareness of possible seismic adjustment measures was not translated into behavior, with all sites demonstrating low adjustment uptake, though the North Americans adopted significantly more adjustments than the other cultures. Thematic analysis of the interview data suggested that adjustment behavior was undermined by anxiety, distrust, distancing self from earthquake risk and fatalistic beliefs. The paper concludes by recommending how culture-specific disaster mitigation plans may be developed to address these factors.

Chapter 26 Consequences of long-term volcanic activity for essential services in Montserrat: challenges, adaptations and resilience

Abstract Long-term volcanic activity at Soufrière Hills Volcano (SHV), Montserrat (1995–ongoing) has created challenges for society and the resilience of the essential services (infrastructure) that support it. This paper explores the consequences, adaptations and resilience of essential services through interviews with their staff. We find that quick fixes for essential service reinstatement in the north of Montserrat have prevailed. Yet, the legacy of this approach inhibits functionality through inadequate facilities and the perception of sites as temporary, stalling investment. Emigration resulted in staff shortages, retraining requirements and challenges for the viability of specialist services. Low-impact hazards exacerbate shortcomings in essential services, causing power cuts, corrosion, and temporary closures of schools, clinics and the airport. Adaptations developed over time include changes to roofing materials, the addition of back-up systems, collaborative working and the development of contingency plans. Resilience of essential services has improved through decentralization, adaptations, and via strong community networks and tolerance of disruptions. Barriers to increasing resilience include the expense of some adaptations and the current reluctance to invest in essential services, hindering development. We offer some lessons for policy and practice to guide post-crisis redevelopment, through engagement with the community and by complementing community-level adaptations with investment to address long-term needs.

Evaluation of Existing Fragility Curves

There is a wealth of existing fragility curves for buildings and infrastructure. The main challenge in using these curves for future applications is how to identify and, if necessary, combine suitable fragility curves from a pool of curves with different characteristics and, often unknown, reliability. The present chapter aims to address this challenge by developing a procedure which identifies suitable fragility curves by firstly assessing their representativeness to the needs of the future application and then assessing the reliability of the most relevant relationships. The latter is based on a novel procedure which involves the assessment of the most significant factors affecting the robustness and quality for each fragility assessment methodology, also presented here. In addition, a decision-tree approach is adopted in order to combine more than one suitable fragility curves. The proposed selection and combination procedures are illustrated here with a simple case study which appraises the impact of different weighting schemes and highlights the importance of a deep understanding of the existing fragility curves and their limitations.

Stochastic coupled simulation of strong motion and tsunami for the 2011 Tohoku, Japan earthquake

This study conducts coupled simulation of strong motion and tsunami using stochastically generated earthquake source models. It is focused upon the 2011 Tohoku, Japan earthquake. The ground motion time-histories are simulated using the multiple-event stochastic finite-fault method, which takes into account multiple local rupture processes in strong motion generation areas. For tsunami simulation, multiple realizations of wave profiles are generated by evaluating nonlinear shallow water equations with run-up. Key objectives of this research are: (i) to investigate the sensitivity of strong motion and tsunami hazard parameters to asperities and strong motion generation areas, and (ii) to quantify the spatial variability and dependency of strong motion and tsunami predictions due to common earthquake sources. The investigations provide valuable insights in understanding the temporal and spatial impact of cascading earthquake hazards. Importantly, the study also develops an integrated strong motion and tsunami simulator, which is capable of capturing earthquake source uncertainty. Such an advanced numerical tool is necessary for assessing the performance of buildings and infrastructure that are subjected to cascading earthquake–tsunami hazards.

Estimating Tsunami-Induced Building Damage through Fragility Functions: Critical Review and Research Needs

Tsunami damage, fragility and vulnerability functions are statistical models which provide an estimate of expected damage or losses due to tsunami. They allow for quantification of risk, and so are a vital component of catastrophe models used for human and financial loss estimation, and for land-use and emergency planning. This paper collates and reviews the currently available tsunami fragility functions in order to highlight the current limitations, outline significant advances in this field, make recommendations for model derivation, and propose key areas for further research. Existing functions are first presented, and then key issues are identified in the current literature for each of the model components: building damage data (the response variable of the statistical model), tsunami intensity data (the explanatory variable), and the statistical model which links the two. Finally, recommendations are made regarding areas for future research and current best practices in deriving tsunami fragility functions (section 6). The information presented in this paper may be used to assess the quality of current estimations (both based on the quality of the data, and the quality of the models and methods adopted), and to adopt best practice when developing new fragility functions.

The Global Earthquake Model Physical Vulnerability Database

There are almost 50 years of research on fragility and vulnerability assessment, both key elements in seismic risk or loss estimation. This paper presents the online database of physical vulnerability models that has been created as part of the Global Earthquake Model (GEM) initiative. The database comprises fragility and vulnerability curves, damage-to-loss models, and capacity curves for various types of structures. The attributes that have been selected to characterize each function, the constraints of setting up a usable database, the challenges in collecting these models, and the current trends in the development of vulnerability models are discussed in this study. The current collection of models leverages upon the outputs of several initiatives, such as GEMs Global Vulnerability Consortium and the European Syner-G project. This database is publicly available through the web-based GEM OpenQuake-platform http://doi.org/10.13117/GEM.DATASET.VULN.WEB-V1.0

The value of multiple earthquake missions: the EEFIT L'Aquila Earthquake experience

In November 2012 EEFIT launched its first ever return mission to an earthquake affected site. The L’Aquila Earthquake site was chosen as this is a recent European event of interest to the UK and European earthquake engineering community. The main aims of this return mission were to document the earthquake recovery process and this paper presents an overview of the post-disaster emergency phase and transition to reconstruction in the Aquila area after the earthquake. It takes an earthquake engineering perspective, highlighting areas mainly of interest to the fields of structural/seismic engineering and reconstruction management. Within the paper, reference is made to published literature, but also to data collected in the field during the return mission that would not otherwise have been available. The paper presents some specific observations and lessons learned from the L’Aquila return mission. However, in light of current international efforts in conducting return missions, the paper ends with some reflections on the value that return missions can provide to the field of earthquake engineering in general, based on the EEFIT L’Aquila experience.

A Different View on Human Vulnerability to Earthquakes: Lessons from Risk Perception Studies

A large proportion of people the world over do nothing or very little to adjust to seismic hazards. Antecedents of seismic adjustment adoption rates relate to fundamental motivations to understand, to belong, to enhance a sense of self-worth, to trust and to control. These motivations are accommodated within socioeconomic and cultural constraints. Understanding such motivations and constraints forms a step in understanding how to facilitate mitigative actions. Through consideration of these issues, the characteristics that define groups less likely to adopt mitigative measures against earthquake hazards are tentatively identified. A UCL-based study that looks to enhance the state-of-the-art knowledge on socio-psychological factors affecting seismic adjustment rates is described. It explores the barriers to seismic adjustment in individuals and small groups in three different countries, and this paper presents some of its initial findings.