Earthquake Loss Research Articles

Exposure forecasting for seismic risk estimation: Application to Costa Rica

This study proposes a framework to forecast the spatial distribution of population and residential buildings for the assessment of future disaster risk. The approach accounts for the number, location, and characteristics of future assets considering sources of aleatory and epistemic uncertainty in several time-dependent variables. The value of the methodology is demonstrated at the urban scale using an earthquake scenario for the Great Metropolitan Area of Costa Rica. Hundreds of trajectories representing future urban growth were generated using geographically weighted regression and multiple-agent systems. These were converted into exposure models featuring the spatial correlation of urban expansion and the densification of the built environment. The forecasted earthquake losses indicate a mean increase in the absolute human and economic losses by 2030. However, the trajectory of relative risk is reducing, suggesting that the long-term enforcement of seismic regulations and urban planning are effectively lowering seismic risk in the case of Costa Rica.

Developing GIS-based earthquake loss model: a case study of Baqiao District, China

Large earthquakes frequently occurred and caused substantial damage and losses in Chinese densely populated urban areas. It is worth clarifying that the existing earthquake loss assessment tools in China do not consider its special characteristics (e.g., tectonics, geology and building inventory). In this paper, an integrated framework for earthquake loss assessment in China is proposed and a geographic information system (GIS)-based system, referred to as China Earthquake Disaster Loss Assessment System, is developed. The individual building is considered as the basic geographical unit and described in three levels (i.e., basic attributes, structural performance parameters, and functional parameters. A three-step data collection method is proposed, and the mobile GIS-based field collection tool is developed. A broad, reasonable, and upgradeable building typology is then presented for the seismic fragility assessment of building blocks. A new economic loss model and casualty model are also presented by considering the characteristics of economics and population. The proposed methodology is implemented in Baqiao District, and the estimation of economic losses and casualties under a scenario earthquake is discussed, which can provide information for urban disaster risk assessment and mitigation.

Macroseismic intensity attenuation in western China

Macroseismic intensity data play an important role in seismic hazard analysis and in developing reliable earthquake loss models. This paper adopts an ellipse model to predict the macroseismic intensity attenuation in both the long-axis and the short-axis directions based on 136 earthquakes recorded throughout western China during 1970–2012. The geometric spreading and energy release of seismic waves are considered in the models proposed in this study. The proposed relation describes the macroseismic intensity simply as a function of the surface wave magnitude, source-to-site distance, and focal depth. This study adopts the focal depth that is not often considered in the current intensity prediction equations in China and uses different functional forms in the long- and short-axis directions. Based on residual analysis and evaluation, a more suitable macroseismic intensity predictive equation was established for western China, and it was compared and discussed with macroseismic intensity prediction equations of other researchers.

The Impact of a Government Risk Pool and an Opt-Out Framing on Demand for Earthquake Protection

This paper describes the design and analysis of a web-based choice experiment that examines how the demand for earthquake protection in Quebec and British Columbia is influenced by the default option and the structure of the insurance plan. Homeowners in both provinces were given the opportunity to purchase protection against earthquake losses when presented with one of the following options: the current private insurance plan, a high deductible private insurance plan, and a proposed public-private risk pool. The default frame was changed so the homeowner could either opt-in by purchasing this coverage or opt-out of being given this protection and receiving a premium discount. Assigning participants to a public-private risk pool rather than the current private insurance plan increases the likelihood of purchasing earthquake protection by 151%. The opt-out frame leads to a likelihood greater than 1.6 of purchasing coverage relative to the opt-in frame when given the same plan structure. The policy implications of this finding are discussed.

Comparative analysis of the earthquake disaster risk of cities in Eastern China based on lethal levels – a case study of Yancheng City, Suqian City and Guangzhou City

Earthquake disaster risk analyses provide significant scientific guidance for reducing earthquake disaster losses etc. The current commonly used method is based on the vulnerability of different types of buildings to evaluate, and may ignore the difference between the seismic resistance of the same type of buildings in different areas. The lethal level considers a series of reasons such as different types of buildings, resulting in different capacities for casualties, the lethal levels of the cities in the same subregion are considerably different and exhibit obvious distribution characteristics. In Yancheng and Suqian, the lethal levels in urban areas are lower than those in rural areas, but the lethal levels in Guangzhou show the opposite trend (the lethal levels are higher in urban areas than in other towns and rural areas). The average lethal level in Guangzhou is 0.3856, that in Suqian is 0.5844, and that in Yancheng is 0.5912. This study based on the lethal levels, conduct a comparative analysis of the earthquake disaster risk of cities throughout eastern China, and a map of the earthquake disaster risk in each city is obtained. The overall lethal level and risk in Guangzhou is much lower than those in Yancheng and Suqian. The main influencing factors in the different cities also diverge. One reason for the lower lethal levels and risk in Guangzhou is that most of the brick-concrete structures are equipped with ring beams and structural columns; conversely, Yancheng and Suqian exhibit higher lethal levels and risk because the brick-concrete structures have ring beams but no structural columns. These maps provide a technical reference and solid scientific and technological support for further earthquake disaster risk analyses and for disaster prevention, mitigation and disaster relief planning, and this method improves the accuracy of rapid postearthquake assessment.

A Quantitative Site-Specific Classification Approach Based on Affinity Propagation Clustering

Investigations made to evaluate the site-effect characteristics and to develop a reliable site classification scheme have received paramount importance for the urban areas planning and reliable site-specific seismic hazard assessment. This paper presents a novel non-objective and data-driven approach for preliminary seismic site-specific classification maps using machine learning (ML) based on affinity propagation (AP) along with a selected set of representative horizontal to vertical spectral ratio (HVSR) curves inside King Saud University (KSU) campus, which is among the main areas in Saudi Arabia. Besides, the proposed model aims to overcome the clustering error due to the dependency of the interpreter’s experience. Measurements of the ambient vibrations were performed to cover the entire campus area by about 307 stations. Recording at each station lasted for 20 minute length and a sample rate of 128 Hz for each station to satisfy the criteria for reliable and unambiguous HVSR results. Frequency and amplification values were used for subsequent site classification by passing messages between data points. The obtained results illustrate that the microtremor spectral ratio can be a remarkably robust tool in determining site effects. Accordingly, the proposed methodology can assist the decision-makers to set the priorities of managing land uses, estimating the earthquake losses, conducting programs for reducing the vulnerability of existing structures, enforcing building codes, planning for emergency response and long-term recovery, and designing and implementing phases of new constructions.

An Analysis of Rural Households' Earthquake-Resistant Construction Behavior: Evidence from Pingliang and Yuxi, China.

Due to the lack of earthquake-resistant rural houses, small and medium earthquakes caused massive casualties in rural China. In 2004, China began implementing the Earthquake Rural Housing Safety Project Policy (ERHSPP) to reduce earthquake losses, mainly promoting the adoption of earthquake-resistant structures in rural residents’ self-built houses through subsidies, training of construction craftsmen, and provision of earthquake-resistant housing drawings. We conducted a field survey, collecting 1169 rural households in Pingliang, Gansu Province, and 1501 rural households in Yuxi, Yunnan Province, China. We studied Earthquake-Resistant Construction Behaviors (E-RCB) by the logistic and the ordered logistic regression models. Results show that government housing subsidy promotes E-RCB of rural households; E-RCB was affected by ERHSPP, positively correlated with economic status and housing earthquake damage; E-RCB was negatively correlated with structure danger, house age, and earthquake experience; and housing earthquake damage, not earthquake experience, strikingly promoted E-RCB in rural China. The results could provide suggestions in communication risk strategies for the government. We suggest the local government should promote local acceptable disaster propaganda, provide hierarchical housing subsidies, pay attention to housing seismic supervision, publish earthquake-resistant housing design drawings, and conduct more earthquake-resistant technical training for rural craftsmen.

Street-block collapsed buildings assessment: A case study of Banqiao District, New Taipei City

After a large-scale earthquake, it induces a large number of building collapses and casualties, especially in urban areas. In order to make prevention and response plans before earthquakes, various earthquake loss estimation systems have been developed. The commonly used units of analysis in those systems include grid and village (or administrative district). However, grids are not consistent with streets/roads, making grid-based analyses impractical for evacuation and rescue road planning. As for village-based analyses, a unit covers large spaces and might fail to point out the precise location of collapsed buildings. Therefore, street block, which is a block surrounded by roads, is proposed by the authors as an alternative. To figure out the better analytical units, this study compared street-block-based analyses and village-based analyses. Banqiao District in Taiwan was used as a case to delineate the street blocks by roads with a width of 6 meters or above. Building collapse assessment under peak ground acceleration (PGA) of 400 Gal and 550 Gal demonstrates that street-block-based analyses outperform village-based analyses in terms of locating the collapsed buildings. Moreover, street blocks are readily available for planning evacuation or rescue roads for their consistence with the road network. Results of this study suggest that in urban areas, the higher-resolution spatial analyses of earthquake loss estimation can be made by street-block-based analyses.

GENERALIZING THE LOG-MOYAL DISTRIBUTION AND REGRESSION MODELS FOR HEAVY-TAILED LOSS DATA

AbstractCatastrophic loss data are known to be heavy-tailed. Practitioners then need models that are able to capture both tail and modal parts of claim data. To this purpose, a new parametric family of loss distributions is proposed as a gamma mixture of the generalized log-Moyal distribution from Bhati and Ravi (2018), termed the generalized log-Moyal gamma (GLMGA) distribution. While the GLMGA distribution is a special case of the GB2 distribution, we show that this simpler model is effective in regression modeling of large and modal loss data. Regression modeling and applications to risk measurement are illustrated using a detailed analysis of a Chinese earthquake loss data set, comparing with the results of competing models from the literature. To this end, we discuss the probabilistic characteristics of the GLMGA and statistical estimation of the parameters through maximum likelihood. Further illustrations of the applicability of the new class of distributions are provided with the fire claim data set reported in Cummins et al. (1990) and a Norwegian fire losses data set discussed recently in Bhati and Ravi (2018).

Variance‐based sensitivity analyses and uncertainty quantification for FEMA P‐58 consequence predictions

AbstractEarthquake loss assessment procedures for individual buildings can be a useful tool for various stakeholders, including building owners, insurers, and lenders. However, it is often not possible to provide complete information for the required inputs to these procedures because there is substantial cost and effort associated with gathering necessary data. It is therefore important to understand how different inputs to these procedures (building information/ground shaking intensity) impact the loss predictions. This can be done via sensitivity analyses. We conduct variance‐based sensitivity analyses for the FEMA P‐58 methodology, a building‐specific seismic performance assessment procedure that is making its way into seismic design and risk analysis practice. We determine how variations in different input variables of the methodology affect predictions of building loss ratio and reoccupancy time, and benchmark calculated sensitivities using the HAZUS earthquake loss estimation methodology . We also quantify additional uncertainty in consequence predictions caused by uncertainty in input variables. We use an example site in downtown Los Angeles and consider a 7‐story and a 14‐story building. Of the six inputs considered in the analyses, building loss ratio predictions are most sensitive to shaking intensity and building age, while reoccupancy time predictions are most sensitive to shaking intensity and the type of lateral system/building period. The largest additional uncertainties in building loss ratio predictions are caused by the building's lateral system or age (or both) being unknown. The results of this study provide an enhanced understanding of the interaction between inputs and consequence predictions of the P‐58 methodology.

Assessing the Blockage Risk of Disaster-Relief Road for a Large-Scale Earthquake

After a large-scale earthquake, the road is susceptible to get blocked by liquefaction or building collapse, and that results in disaster-relief difficulty. This study adopted two earthquake loss estimation systems in Taiwan, and the risk of road blockage caused by liquefaction or building collapse was calculated separately. A new modeling was proposed, and the comparisons of the results of a single factor and that of the joint factors were made. Four scenarios of peak ground acceleration (PGA) = 250, 400, 550, 750 Gal were tested. The result shows that the probability of road blockage due to liquefaction almost reaches the maximum when PGA hits 400 Gal. On the other hand, the probability of road blockage due to building collapse increases if PGA increases. The joint probability of road blockage due to liquefaction and building collapse can improve the underestimation when using either one factor, and it can evaluate the risk more realistically. At present, there is no risk assessment modeling considering two important factors for disaster-relief road planning in Taiwan. This study provides a simple and comprehensive disaster-relief road risk assessment modeling to make better emergency rescue plans. In addition, it can provide the information for conducting seismic strengthening policy for both sides of the disaster-relief road that can reduce the risk of obstacles to disaster-relief roads.

Cost\u2013benefit analyses to assess the potential of Operational Earthquake Forecasting prior to a mainshock in Europe

In the past couple of decades, Operational Earthquake Forecasting (OEF) has been proposed as a way of mitigating earthquake risk. In particular, it has the potential to reduce human losses (injuries and deaths) by triggering actions such as reinforcing earthquake drills and preventing access to vulnerable structures during a period of increased seismic hazard. Despite the dramatic increases in seismic hazard in the immediate period before a mainshock (of up to 1000 times has been observed), the probability of a potentially damaging earthquake occurring in the coming days or weeks remains small (generally less than 5%). Therefore, it is necessary to balance the definite cost of taking an action against the uncertain chance that it will mitigate earthquake losses. In this article, parametric cost–benefit analyses using a recent seismic hazard model for Europe and a wide range of inputs are conducted to assess when potential actions for short-term OEF are cost–beneficial prior to a severe mainshock. Ninety-six maps for various combinations of input parameters are presented. These maps show that low-cost actions (costing less than 1% of the mitigated losses) are cost–beneficial within the context of OEF for areas of moderate to high seismicity in the Mediterranean region. The actions triggered by OEF in northern areas of the continent are, however, unlikely to be cost–beneficial unless very large increases in seismicity are observed or very low-cost actions are possible.

Application of the SP-BELA methodology to RC residential buildings in Italy to produce seismic risk maps for the national risk assessment

This article deals with the application of an analytical methodology for the large-scale vulnerability assessment of reinforced concrete frame buildings in Italy. This methodology is known in the technical literature with the acronym SP-BELA (Simplified Pushover-Based Earthquake Loss Assessment) and has been adopted by the Eucentre research group to contribute to the production of the seismic risk maps in Italy, published in the National Risk Assessment document. The Italian maps were elaborated using the IRMA platform (Italian Risk MAps), which is a web platform developed by Eucentre. The IRMA platform is only addressed to the scientific community who can use it to share data, methods, and models for the evaluation of the seismic risk in Italy (Borzi et al. in Piattaforma IRMA Italian Risk MAps, 2018; Dolce et al. in Mappe di rischio per il territorio Italiano, 2019a; Faravelli et al. in Italian platform for seismic risk and damage scenario evaluation, 2019a, Borzi et al. in Bull Earthq Eng, 2020, Dolce et al. Bull Earthq Eng, 2020). SP-BELA defines the non-linear behaviour of a random population of buildings through a simplified pushover and a displacement-based procedure. Specifically, displacement capacity limits are identified on the pushover curve and then they are compared with the displacement demand from a response spectrum of each building in the random population. In this way, it is possible to define the probability of exceedance of the damage limits and hence generate the fragility curves. Then, the resulting curves have been calibrated by comparing the damage data observed on the reinforced concrete buildings with the damage analytically calculated with SP-BELA for the earthquakes of Molise 2002 and L’Aquila 2009. The final curves have been uploaded into the IRMA platform and used to produce damage maps for the entire national territory.

Post-processing HAZUS earthquake damage and loss assessments for individual buildings

Building damage probabilities are invaluable for assessing short-term losses from natural hazards. In many countries however, the individual building level data required for assessing reliable damage are usually unavailable. This paper shows how the post-processing of aggregate HAZUS earthquake damage assessments can yield building-level damage probabilities. On the basis of three plausible scenarios for Northern Israel, we generate and visualize a building-level combined damage probability index. We use the tools of exploratory spatial data analysis to purge any causal influences in the spatial pattern of these calculated damage probabilities. The costs and benefits of our approach are discussed.

Comparative assessment of seismic collapse risk for non-ductile and ductile bridges: a case study in China

Risk assessment plays an important role in quantifying earthquake loss and has been widely used in the field of seismic engineering. However, current studies of the risk assessment rarely consider the different failure modes of piers (i.e., flexure failure, flexure-shear failure and shear failure), which will lead to an excessive estimation for the seismic performance and collapse safety of the reinforced concrete girder bridges. This paper focuses on studying the seismic behavior of bridges considering different failure modes and comparing the seismic collapse risk of the bridges with and without ductile detailing. The numerical analysis is performed in an open source finite element (FE) software framework, Open Sees. Nonlinear shear springs are introduced into the FE models of reinforced concrete (RC) columns to accommodate the shear and flexural-shear effect of the bridges. The accuracy of the FE models is validated by using the existing results of static cyclic-loading experiments. Case studies are conducted for two categories of the girder bridges, which are designed based on new and old seismic design criteria in China, respectively. The collapse fragility curves are developed by using the incremental dynamic analysis method, which considers the uncertainties of the ground-motion characteristics and the structural material parameters. Based on the seismic hazard curve of a designated region, a comparative assessment of the seismic collapse risk is performed regarding mean annual collapse rate for the non-ductile and ductile bridges. The main results of the paper are: (1) The FE model with the nonlinear shear spring provides an acceptably accurate solution for simulating the initial stiffness, shear failure point, strength degradation slope and residual shear strength of the RC columns; (2) The structural collapse safety is shown to be related not only to the collapse probability of the bridges but also to the occurring probability of the ground motion intensity exceeding a given threshold; (3) The mean annual collapse rate of the ductile girder bridges is significantly smaller than that of the non-ductile girder bridges. The results can be used as a reference to implement specific policies for appraising and mitigating the seismic risk of existing RC bridges.

IRMA platform for the calculation of damages and risks of Italian residential buildings

Italian Risk MAps (IRMA) is an innovative IT platform developed by European centre for training and research in earthquake engineering (Eucentre) with funds of the Italian Civil Protection Department, and addressed to the scientific community. IRMA allows data sharing, methods and models aimed to evaluate the seismic risk of Italian residential buildings, in order to comply with the requirements of the “Sendai Framework for Disaster Risk Reduction 2015–2030” (Sendai Framework). IRMA uses OpenQuake, a calculation engine developed as part of the Global Earthquake Model, to evaluate earthquake loss estimation. The user can create and upload different exposure/vulnerability databases as well as different sets of fragility curves on the platform. The hazard used in the platform is the MPS04 hazard model, developed by National Institute of Geophysics and Volcanology that is actually the reference hazard map for the Italian code regulation. IRMA is extremely flexible: by combining the different exposure databases with all the possible sets of fragility curves, the user can produce maps of conditional damage (i.e. the return period is selected) or unconditional damage (i.e. an observation time window is selected). Damage scenarios can also be performed by using shakemaps of seismic events as input. The shakemaps, preloaded in the platform, are those referred to the recent seismic events in Italy. The article describes the context in which IRMA was developed, its features and architecture. IRMA was used in 2018 by DPC to produce the National Risk Assessment, in agreement with EU decision 1313/2013.

Exploring the impact of epistemic uncertainty on a regional probabilistic seismic risk assessment model

Probabilistic earthquake loss models are widely used in the (re)insurance industry to assess the seismic risk of portfolios of assets and to inform pricing mechanisms for (re)insurance contracts, as well as by international and national organizations with the remit to assess and reduce disaster risk. Such models include components characterizing the seismicity of the region, the ground motion intensity, the building inventory, and the vulnerability of the assets exposed to ground shaking. Each component is characterized by a large uncertainty, which can be classified as aleatory or epistemic. Modern seismic risk assessment models often neglect some sources of uncertainty, which can lead to biased loss estimates or to an underestimation of the existing uncertainty. This study focuses on exploring and quantifying the impact of a number of sources of uncertainties from each component of an earthquake loss model to the loss estimates. To this end, the residential exposure of Guatemala and Guatemala City were used as case studies. Moreover, a comparison of the predicted losses for an insured portfolio in the country between OpenQuake-engine and a vendor catastrophe platform was performed, assessing the potential application of OpenQuake in the (re)insurance industry. The findings from this study suggest that the uncertainty in the hazard component has the most significant effect on the loss estimates.

Seismic vulnerability assessment and loss estimation in Cephalonia and Ithaca islands, Greece, due to earthquake events: A case study

In this paper an estimation of seismic losses for various seismic scenarios of the Cephalonia and Ithaca islands, Greece, is proposed. The area under consideration is located in one of the most seismically active regions with the most damage and human casualties in recent history. Seismic losses were estimated at buildings, economic and human level. The estimation method is based on the assumption that seismic risk depends on vulnerability and seismic hazard. Vulnerability estimation was done by detailed fragility curves representing the structures in the area. Subsequently, losses in the wider area were estimated for various seismic risk scenarios. Parametric scenarios for different earthquake level and retrofit strategy were performed. The earthquake loss estimation software ELER (Earthquake Loss Estimation Routine) was used for the calculations. The numerical results extracted and their comparison with results from actual earthquake loss showed that losses can be estimated in the same order of magnitude as the real data and thus enable the state to be better prepared to deal with future earthquakes more effectively.

Seismic vulnerability comparison between rural Weinan and other rural areas in Western China

Generally, the anti-seismic capacity of rural buildings in China is poor due to their irregular design and construction. On the basis of historical destructive earthquake records, corresponding earthquake loss evaluation compilations (1993–2016), field investigations, and remote sensing interpretation, building structures in rural Weinan are classified into two types and analyzed to acquire the seismic vulnerability matrices by employing the fitting method of beta probability density function (BPDF). Results show that BPDF can well reveal the probability density distribution of seismic damage index, and also the damage ratio obtained agrees well with the description of damage degrees in Chinese macroseismic intensity scale.The vulnerability indexes in rural areas of Yunnan, Sichuan, Qinghai provinces and in Weinan City (Shaanxi province) were calculated and a comparison of aseismic ability was made. Results show that, among the rural areas in Western China, the aseismic abilities of traditional buildings in rural Weinan are the lowest while those of masonry buildings are highest. Moreover, potential losses in rural Weinan are estimated on the assumption that a scenario earthquake with a magnitude Ms 6¾ hit Weinan City, proposed by the UK-China Collaboration programme ‘‘Increasing Resilience to Natural Hazards in Earthquake-Prone regions in China”. It was found that the damage ratios obtained captured the distribution of the aseismic abilities of the rural buildings and therefore improved the accuracy of the loss assessment, which provides scientific basis for the scenario narratives. What we discovered in this paper is also helpful in future earthquake damage prediction and enhancement of public awareness on earthquake resistance.

Analytical evaluation of damage probability matrices for hill-side RC buildings using different seismic intensity measures

In the present study seismic response and vulnerability of hill-side RC buildings, often observed in the Indian Himalayan region as well as in some other parts of the world were analytically investigated using non-linear dynamic analyses. The conducted analyses led to the development of seismic fragility functions based on three different ground-motion intensity measures, viz. peak ground acceleration, spectral acceleration at the fundamental building period, and average spectral accelerations over a range of periods. In addition to the different code design levels that are considered in the assessment, the choice of the ground-motion intensity measure as well as the structural configuration type of these hill-side buildings show quite significant effects on the resulted damage probabilities of different damage states, and thus on the computed mean damage ratio. The peak ground acceleration results in a significant overestimation of the mean damage ratio for the maximum considered earthquake hazard level when compared with the spectral acceleration-based intensity measures. On the other hand, the irregular structural configuration of hill-side buildings alone results in a significantly higher mean damage ratio when compared with regular structural configuration. In addition to the design code level, the need to incorporate both of these effects, i.e. the choice of ground-motion intensity measure and irregular structural configurations of hill-side buildings, in the next generation of earthquake loss estimation studies and software tools is underlined.