An Applied Method for General Regional Seismic Loss Assessment—With A Case Study in Los Angeles County

We describe the formulation and application of an integrated general regional seismic loss assessment (RSLA) method for buildings in seismic regions. An efficient method for RSLA is valuable for engineers involved in city planning, risk management, and insurance dealings. In contrast to previously reported methods, the framework presented herein is hazard-based and utilizes a regional rapid seismic hazard deaggregation tool that allows regional assessment to be conducted more efficiently. The proposed technique is implemented as an example to assess general regional seismic loss in Los Angeles County for a ground motion hazard with 10% probability of exceedance in 50 years.     

Sustainability of Highway Bridge Networks Under Seismic Hazard

In order to evaluate the seismic risk of transportation networks, it is necessary to develop a methodology that integrates the probabilities of occurrence of seismic events in a region, the vulnerability of the civil infrastructure, and the consequences of the seismic hazard to the society, environment, and economy. In this article, a framework for the time-variant seismic sustainability and risk assessment of highway bridge networks is presented. The sustainability of the network is quantified in terms of its social, environmental, and economic metrics. These include the expected downtime, expected energy waste and carbon dioxide emissions, and the expected loss. The methodology considers the probability of occurrence of a set of seismic scenarios that reflect the seismic activity of the region. The performance of network links is quantified based on individual bridge performance evaluated through fragility analyses. The sustainability and risk depend on the damage states of both the links and the bridges within the network following an earthquake scenario. The time-variation of the sustainability metrics and risk due to structural deterioration is identified. The approach is illustrated on a transportation network located in Alameda County, California.     

On exposure,vulnerability and violence: Spatial distribution of risk factors for climate change and violent conflict across Kenya and Uganda

Recent studies discuss the link between climate change and violent conflict, especially for East Africa. While there is extensive literature on the question whether climate change increases the risk of violent conflict onset, not much is known about where a climate-conflict link is most likely to be found. We address this question by analyzing the spatial distribution of the factors commonly associated with a high exposure and vulnerability to climate change, and a high risk of violent conflict onset in Kenya and Uganda. Drawing on recent literature and quantitative data for the period 1998–2008, we develop various specifications of a composite risk index (CRI) with a spatial resolution of half a degree for Kenya and Uganda in the year 2008. A quantitative comparison with conflict data for the year 2008 provides support for the composite risk index. Finally, the composite risk index is contrasted with the findings of three qualitative case studies, which provide mixed support for the index and help to identify its strengths and weaknesses as well as conceptual needs for further quantitative studies on climate change and violent conflict.     

Perceived Risk and Citizen Preferences for Governmental Management of Routine Hazards

Risk perceptions are important to the policy process because they inform individuals’ preferences for government management of hazards that affect personal safety, public health, or ecological conditions. Studies of risk in the policy process have often focused on explicating the determinants of risk perceptions for highly salient, high consequence hazards (e.g., nuclear energy). We argue that it is useful to also study more routinely experienced hazards; doing so shows the relevance of risk perceptions in individuals’ daily lives. Our investigation focuses on the impact perceived risk has on citizens’ preferences over hazard management policies (as distinct from identifying risk perception determinants per se). We use a recursive structural equation model to analyze public opinion data measuring attitudes in three distinct issue domains: air pollution, crime, and hazardous waste storage and disposal. We find that citizens utilize perceived risk rationally: greater perceived risk generally produces support for more proactive government to manage potential hazards. This perceived risk–policy response relationship generally holds even though the policy options respondents were asked to consider entailed nontrivial costs to the public. The exception seems to be when individuals know less about the substantive issue domain.     

Dynamic optimization of horticulture among the Muscogee Creek Indians of the southeastern United States

This paper reviews archaeological applications of optimization theory applied to resource use. A model of agricultural corn production is derived for a single Muscogee Creek Indian town (CA 1725–1825) which was situated in the southeastern United States. The corn productivity model is based on soil depletion, soil variation, known locations of horticultural fields, population size, and nutritional requirements. The corn productivity model shows that corn production varied significantly between 1725 and 1825. The residents of the town shifted their horticultural gardens in order to maintain a nutritional minimum. The model was compared to the marginal value theorem and expectations derived from risk minimization models. Residents of Cussetuh abandoned their horticultural fields well before the instantaneous long-term average rate of production for the habitat. The model shows that the residents of Cussetuh were risk minimizers and were not maximizing the long term average rate of corn yield in their gardens.     

Archaeological markers of agricultural risk management

Managing agricultural risk, or variance in annual production, is a priority for farmers and herders. This article reviews the ethnographic and historical literature on agricultural risk management and identifies diversification and intensification as two distinct approaches to managing risk. Quantitative analysis of plant and animal remains from archaeological sites produces robust datasets that can be used to test predictions of risk management models related to diversification and intensification strategies. I present a variety of established and novel paleoethnobotanical and zooarchaeological measures that have implications for risk management and argue that multiple lines of evidence are needed to identify risk-management practices from archaeological remains. The article concludes with a case study of the multiperiod urban center of Gordion in central Turkey, where quantitative analysis of plant and animal remains demonstrates diachronic changes in agricultural risk management over 3000 years of occupation.     

Numerical Fragility Analysis of Vertical-Pile-Supported Wharves in the Western United States

This study develops seismic fragility curves for vertical-pile-supported wharves commonly found in the western United States. Nonlinear time-history analyses of a two-dimensional numerical model under two ground motion suites are performed. The results show that the jumbo container cranes increase by 10.8% in the wharf deck drift. By using the experiment-based limit states, the proposed fragility curves demonstrate that, at a PGA of 0.50 g, the probabilities of exceeding slight, moderate, extensive, and complete limit states are approximately 23.0%, 7.0%, 4.0%, and 3.0%, respectively, while at a PGA of 1.00 g, the exceeding probabilities increase to 44.0%, 19.0%, 14.0%, and 11.0%, respectively.     

The Impact of Flood-Induced Scour on Seismic Fragility Characteristics of Bridges

Earthquake in the presence of flood-induced scour is a critical multihazard scenario for bridges located in seismically-active, flood-prone regions. The present article evaluates seismic performance of four example reinforced concrete bridges when they are pre-exposed to regional flood hazards. Nonlinear time history analyses of the example bridges are performed for a suite of ground motion time histories in the presence and absence of scour expected from different intensity flood events. Fragility analysis is performed to develop seismic fragility curves of the example bridges for various scour depths. Results show nonlinear increase in bridge seismic fragility with increase in scour depth.     

Choices and Criteria for Seismic Strengthening

Risk assessment is affected by large uncertainties, depending on hazard, structure, damage, and loss analysis. Crucial problems and choices may refer to: (a) hazard parameters, including the definition of appropriate ground motion levels and of their probability to occur; (b) level of knowledge about materials, geometry, detailing; (c) assessed damage and failure modes; and (d) resulting potential for step changes in performances.

The cost of attaining a high level of knowledge may significantly reduce the remaining resources, it is therefore important to favor resilient solutions with a creative adoption of appropriate strengthening strategies.

In this framework, this article discusses the possible criteria for the mitigation of seismic risk and some of the alternative choices that may be adopted for strengthening, with reference to:

(a)?the modification of damage and collapse modes strengthening individual elements or locallyincreasing the deformation capacity;

(b)?the insertion of additional systems resisting to horizontal actions;

(c)?the introduction of base isolation, with the objective of capacity-protecting the existingstructure;

(d)?the reduction of displacement demand by added damping or introducing tuned masssystems.

Alternative strengthening choices lead to different protection levels and imply different performances that are, in general, represented by non linear or step functions of a cost parameter of the intervention. From these considerations, conceptual “structure driven” strengthening criteria, based on a logical use of resources, are discussed.     

Critical Issues in Earthquake Scenario Loss Modeling

The assessment of human or economic losses due to single events (scenario) may effectively support decision makers in the development of important risk mitigation actions. The study presented herein sheds light on several problems and limitations in the current practice of scenario loss modeling, such as: the number of simulations required to achieve convergence; epistemic and aleatory uncertainty in the ground motion prediction and vulnerability models; and consideration of the earthquake rupture geometry. These issues are investigated using the Metropolitan Area of Lisbon (Portugal), and it has been observed that distinct assumptions in the loss modeling can lead to considerably different results. The findings of this study are also pertinent for probabilistic seismic risk analyses in which a large number of stochastically generated events are employed to assess probabilistic losses.