Earthquake Loss Models Research Articles

ShakeMap Atlas 4.0 and AtlasCat: An Archive of the Recent and the Historical Earthquake ShakeMaps, and Impacts for Global Hazard Analyses and Loss Model Calibration

Abstract Archival earthquake studies often focus on event and source characteristics for use in earthquake catalogs, seismotectonic understanding, and ground-motion studies—many of these targeting better constraints for probabilistic seismic-hazard analyses. The ShakeMap Atlas, in contrast, focuses on spatial distribution of shaking for the historical events, providing the best constraints at all locations that experienced significant shaking for each event, facilitating analyses of human experience, damage, and induced hazards (ground failure). The aim of the Atlas is to gain a general understanding and depiction of the shaking distribution for a suite of canonical earthquakes, and, coupled with loss data for each event, to provide a basis for earthquake loss model calibration, among other uses. Although the initial motivation for developing the ShakeMap Atlas was calibrating the U.S. Geological Survey (USGS) Prompt Assessment of Global Earthquakes for Response system, over time, the Atlas has proved to be a useful tool for its users, and, as such, its scope has been vastly expanded in this newest version. The fourth version of the USGS ShakeMap Atlas is an openly available compilation of over 14,000 ShakeMaps of significant global earthquakes between 1900 and 2020. This revision includes: (1) the latest version of the ShakeMap software that provides refined uncertainty estimations and improved methods to combine macroseismic observations with updated ground-motion models; (2) an updated earthquake source catalog; (3) a refined strategy to select suites of prediction and conversion equations based on a new seismotectonic regionalization scheme; and (4) expanded macroseismic intensity and ground-motion datasets. We also tabulate reported economic losses and fatalities for Atlas events where such data are openly available. These changes make the new ShakeMap Atlas a self-consistent, calibrated catalog invaluable for investigating near-source ground motions, as well as seismic hazard, scenario, risk, and loss-model development and testing.

Analyzing the Temporal Variation in Macroseismic Intensity Rating Values and Predicting Macroseismic Intensity on the Tibetan Plateau

ABSTRACT China has relatively rich macroseismic isoseismal maps, which play an important role in seismic hazard analysis and the development of reliable earthquake loss models. The macroseismic intensity is assessed based on the Chinese Seismic Intensity Scale, which is constantly being revised as research progresses and the seismic defense capability is enhanced. To investigate whether intensity rating values show consistency across time in statistical significance, this study collected 543 isoseismal lines for 216 earthquakes on the Tibetan Plateau from 1960 to 2020. Taking intensity prediction equations (IPEs) as a reference, statistical tests of the residuals indicate that there is temporal variation in intensity rating values, which is inconsistent with the default assumption that intensity rating values are consistent for different time periods when developing IPEs. Therefore, we analyze the characteristics of intensity rating values by statistical tests and investigate the mechanism by which the temporal variation in intensity rating values affects IPEs by residual decomposition. The results show that despite the temporal variation in intensity rating values, they can still be used to develop IPEs, and that temporal variability can be reduced by adjustment. Finally, we obtain the regression process of IPEs based on the partially nonergodic assumption considering the temporal variation in intensity rating values, and perform a case study, using the Tibetan Plateau as an example.

Detailed Structural Characterization of Existing RC Buildings for Seismic Exposure Modelling of the Lisbon Area

As many European countries, the Portuguese territory is a region of moderate seismicity, and a large part of its building stock includes reinforced concrete (RC) buildings built before the introduction of modern seismic codes (<1983s). Currently, the Lisbon building stock is composed of 45% of RC buildings, of which 71% were built in such a construction period. Being designed to only sustain gravitational loads and without adequate lateral load resistance, these buildings are likely to be severely damaged during an earthquake. This highlights the need to propose reliable seismic risk assessment and earthquake loss models for such structures. In this context, the development of an exposure model which quantifies the building stock susceptible to be seismically damaged, in terms of structural characteristics, spatial location, and occupancy, is of major importance. The main purpose of this paper is to contribute the definition of a building exposure model for the city of Lisbon, focusing on a detailed structural characterization of these typologies. It starts with an extensive collection and analysis of design blueprints of existing buildings in two Lisbon’s neighborhoods: Alvalade and Benfica, which were found to be representative of the RC building stock in the city. Then, the information collected is scrutinized and statistically post-processed through probability distributions that provide a clear insight on the RC typologies and their structural characteristics. These results can be used in the future for the development of a numerical models and to derive fragility and vulnerability models, fundamental to conducting seismic risk analyses.

Epistemic uncertainty of probabilistic building exposure compositions in scenario-based earthquake loss models

In seismic risk assessment, the sources of uncertainty associated with building exposure modelling have not received as much attention as other components related to hazard and vulnerability. Conventional practices such as assuming absolute portfolio compositions (i.e., proportions per building class) from expert-based assumptions over aggregated data crudely disregard the contribution of uncertainty of the exposure upon earthquake loss models. In this work, we introduce the concept that the degree of knowledge of a building stock can be described within a Bayesian probabilistic approach that integrates both expert-based prior distributions and data collection on individual buildings. We investigate the impact of the epistemic uncertainty in the portfolio composition on scenario-based earthquake loss models through an exposure-oriented logic tree arrangement based on synthetic building portfolios. For illustrative purposes, we consider the residential building stock of Valparaíso (Chile) subjected to seismic ground-shaking from one subduction earthquake. We have found that building class reconnaissance, either from prior assumptions by desktop studies with aggregated data (top–down approach), or from building-by-building data collection (bottom–up approach), plays a fundamental role in the statistical modelling of exposure. To model the vulnerability of such a heterogeneous building stock, we require that their associated set of structural fragility functions handle multiple spectral periods. Thereby, we also discuss the relevance and specific uncertainty upon generating either uncorrelated or spatially cross-correlated ground motion fields within this framework. We successively show how various epistemic uncertainties embedded within these probabilistic exposure models are differently propagated throughout the computed direct financial losses. This work calls for further efforts to redesign desktop exposure studies, while also highlighting the importance of exposure data collection with standardized and iterative approaches.

Variable-resolution building exposure modelling for earthquake and tsunami scenario-based risk assessment: an application case in Lima, Peru

Abstract. We propose the use of variable resolution boundaries based on central Voronoi tessellations (CVTs) to spatially aggregate building exposure models for risk assessment to various natural hazards. Such a framework is especially beneficial when the spatial distribution of the considered hazards presents intensity measures with contrasting footprints and spatial correlations, such as in coastal environments. This work avoids the incorrect assumption that a single intensity value from hazards with low spatial correlation (e.g. tsunami) can be considered to be representative within large-sized geo-cells for physical vulnerability assessment, without, at the same time, increasing the complexity of the overall model. We present decoupled earthquake and tsunami scenario-based risk estimates for the residential building stock of Lima (Peru). We observe that earthquake loss models for far-field subduction sources are practically insensitive to the exposure resolution. Conversely, tsunami loss models and associated uncertainties depend on the spatial correlations of the hazard intensities as well as on the resolution of the exposure models. We note that for the portfolio located in the coastal area exposed to both perils in Lima, the ground shaking dominates the losses for lower-magnitude earthquakes, whilst tsunamis cause the most damage for larger-magnitude events. For the latter, two sets of existing empirical flow depth fragility models are used, resulting in large differences in the calculated losses. This study, therefore, raises awareness about the uncertainties associated with the selection of fragility models and spatial aggregation entities for exposure modelling and loss mapping.

Toward a uniform earthquake loss model across Central America

This study presents a probabilistic earthquake loss model for Central America, which is used to evaluate the indicators of the Sendai Framework for Disaster Risk Reduction (SFDRR). The exposure, vulnerability, and hazard components of the model were established using a uniform methodology for all the countries. Earthquake risk is expressed according to three indicators: mortality (A-1), population affected (B-1), and economic losses (C-1). Exposure results indicate that over 9.1 million structures (with an economic value of US$635 billion) are exposed to seismic hazard in the region. The risk results indicate an average annual human loss of 0.7 fatalities per 100,000 inhabitants, an average number of 35 people affected per 100,000 inhabitants, and an average annual economic loss of US$990 million. This represents 0.43% and 0.16% of the regional gross domestic product (GDP) and total replacement value, respectively. Guatemala, Nicaragua, and El Salvador present the highest risk, contributing with 75% of the absolute economic losses and 84% of the average annual fatalities in the region.

Impact of exposure spatial resolution on seismic loss estimates in regional portfolios

The spatial resolution of exposure data has a substantial impact on the accuracy and reliability of seismic risk estimates. While several studies have investigated the influence of the geographical detail of urban exposure data in earthquake loss models, there is also a need to understand its implications at the regional scale. This study investigates the effects of exposure resolution on the European loss model and its influence on the resulting loss estimates by simulating dozens of exposure and site models (630 models) representing a wide range of assumptions related to the geo-resolution of the exposed asset locations and the associated site conditions. Losses are examined in terms of portfolio average annual loss (AAL) and return period losses at national and sub-national levels. The results indicate that neglecting the uncertainty related to asset locations and their associated site conditions within an exposure model can introduce significant bias to the risk results. The results also demonstrate that disaggregating exposure to a grid or weighting/relocating exposure locations and site properties using a density map of the built areas can improve the accuracy of the estimated losses.

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.

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.

Comparative earthquake loss estimations for high-code buildings in Istanbul

The paper presents the probabilistic and scenario based earthquake loss estimations for the case that the hazard and building inventory inputs are kept the same whereas the damage functions as well as the seismic demand estimation method are changed in an earthquake loss model. Spectral acceleration-displacement based damage assessments by alternating damage functions and inelastic demand evaluation methods are performed for high-code buildings in Istanbul. The buildings are mid- and high-rise, reinforced concrete, moment-resisting frames that are assumed to be designed in accordance with the provisions of Turkish Earthquake Resistant Design Code (1998). Three damage models, i.e. structural capacity and fragility curves, are employed for each building class: Expert judgment based capacity and fragility functions; HAZUS's high-code seismic design level capacity and fragility functions; and Capacity and fragility functions derived based on nonlinear analyses of code complying RC frames. Inelastic spectral displacement demands are computed with three methods: Capacity Spectrum Method, Modified Acceleration-Displacement Response Spectrum Method, and Displacement Coefficient Method. Analyses are realized under site-specific ground motions based on a state-of-the-art hazard model for eight return periods ranging from 100 to 2475 years as well as for an Mw = 7.5 scenario earthquake. Probabilistic loss curves for each case are developed. Estimated average annual losses (AAL) and loss ratios (AALR) are compared. Grid and district based maps illustrating the spatial distributions of estimated long term average losses per year and the loss ratios are presented. The estimated annualized loss ratios at district level in the city are compared to the earthquake insurance premium rates.

Probabilistic earthquake loss model for residential buildings in Tehran, Iran to quantify annualized earthquake loss

In this study, a comprehensive loss model using the most recent census data (2016) together with the updated earthquake catalog (till 2018) is employed to estimate the direct expected annualized loss of residential buildings in Tehran, Iran. This is an important parameter to determine insurance premium or to identify relative risk in a region. For this purpose, a fully probabilistic seismic loss model based on the stochastic event-based approach is adopted. The assessment includes the development of a robust approach to quantify the seismic hazard by taking into account dynamic soil response, compiling a high quality exposure of residential building and considering the most appropriate vulnerability models for different building classes. The result shows that average annual loss of building stock is around $0.331 billion which is about 0.29% of total exposed economic value. Also, the relative risk map of the region is presented in term of the annualized earthquake loss ratio. It demonstrates that the seismic risk in the middle and southern part of the city are much higher. In addition, a disaggregation analysis regarding the building typologies is performed to identify the most vulnerable building classes. The result indicates that the masonry and low quality steel and concrete structures with poor designing specification are the most vulnerable building classes. Majority of the buildings in southern part of Tehran are of these types, where accommodating low-income residents. The finding from this study can be used by local authorities, government and insurance sector in order to develop effective risk mitigation plans and a robust insurance scheme for Tehran, Iran. In addition, the presented approach can be applied in other cities with different socio-economic conditions.

Development of a probabilistic earthquake loss model for Iran

Iran is located in one of the most seismically active regions of the world. This high seismicity combined with densely populated regions has led to several destructive earthquakes in the past, such as the M7.4 Tabas (1978), M7.4 Manjil–Rudbar (1990), or the M6.6 Bam (2003). Seismic hazard and risk assessment can provide critical information to decision makers for the development of efficient risk reduction measures. In this study, exposure models for the residential, commercial and industrial building stock were developed using recent housing census information, socio-economic data and the judgement of local experts. For each building class in the exposure model, a set of fragility and vulnerability models was derived using nonlinear time history analysis and ground motion records from the region. The exposure and vulnerability models were combined with the recently released Earthquake Model for the Middle East (EMME) to estimate probabilistic earthquake losses using the OpenQuake-engine. These results identify the regions within the country with the highest risk, the most vulnerable building classes, and the expected economic losses for a number of return periods.

Macroseismic intensity attenuation in Iran

Macroseismic intensity data plays an important role in the process of seismic hazard analysis as well in developing of reliable earthquake loss models. This paper presents a physical-based model to predict macroseismic intensity attenuation based on 560 intensity data obtained in Iran in the time period 1975–2013. The geometric spreading and energy absorption of seismic waves have been considered in the proposed model. The proposed easy to implement relation describes the intensity simply as a function of moment magnitude, source to site distance and focal depth. The prediction capability of the proposed model is assessed by means of residuals analysis. Prediction results have been compared with those of other intensity prediction models for Italy, Turkey, Iran and central Asia. The results indicate the higher attenuation rate for the study area in distances less than 70km.

A Prototype Operational Earthquake Loss Model for California Based on UCERF3-ETAS – A First Look at Valuation

We present a prototype operational loss model based on UCERF3-ETAS, which is the third Uniform California Earthquake Rupture Forecast with an Epidemic Type Aftershock Sequence (ETAS) component. As such, UCERF3-ETAS represents the first earthquake forecast to relax fault segmentation assumptions and to include multi-fault ruptures, elastic-rebound, and spatiotemporal clustering, all of which seem important for generating realistic and useful aftershock statistics. UCERF3-ETAS is nevertheless an approximation of the system, however, so usefulness will vary and potential value needs to be ascertained in the context of each application. We examine this question with respect to statewide loss estimates, exemplifying how risk can be elevated by orders of magnitude due to triggered events following various scenario earthquakes. Two important considerations are the probability gains, relative to loss likelihoods in the absence of main shocks, and the rapid decay of gains with time. Significant uncertainties and model limitations remain, so we hope this paper will inspire similar analyses with respect to other risk metrics to help ascertain whether operationalization of UCERF3-ETAS would be worth the considerable resources required.

Pricing Earthquake Catastrophe Options Based on the Mixed-Multinomial Tree Model

The discrete time model we propose for option pricing, called the mixed-multinomial tree model (MMTM), extends the conventional multinomial tree model by assuming that both the number of branches of nodemand possible valuesuiare random variables during each period. The conventional multinomial tree model cannot be used to describe the accumulated loss process in earthquakes because earthquakes occur randomly and different main shocks may have different aftershocks. We therefore apply the MMTM to build an accumulated earthquake loss model in earthquake catastrophe options. We study option pricing for such a model and obtain a call option pricing formula.

Application of Fuzzy Pattern Recognition of Seismic Damage to Concrete Structures

AbstractThere has been a long-standing desire to identify classes or groupings of buildings that exhibit similar characteristics in response to seismic events. Regional earthquake loss models, post-earthquake safety evaluations, and rapid visual screening of buildings for potential seismic hazards all utilize building damage patterns in some form. Difficulty arises in characterizing seismic building damage due to the inherent uncertainty in both the occurrence of seismic events and uncertainties related to building responses. Various trends in building performance, often based on building characteristics, are frequently listed in the literature. For example, older structures are expected to perform less well than those designed to more recent design codes; however, it remains difficult to characterize building damage due to the rarity and somewhat limited documentation of earthquake building damage. The earthquake engineering field, in its current state, is dominated by probabilistic and/or deterministic ...

Convex Set and Probabilistic Model-Based Hybrid Earthquake Loss Assessment Method

In order to make the most of the advantages of probabilistic model and non-probabilistic model, a hybrid earthquake loss assessment method based on convex model and probabilistic model was proposed. The exceeding probability of earthquake loss bounds within convex model was derived based on the probabilistic earthquake loss assessment model proposed by PEER. Moreover, the uncertainties of repair cost and collapse probability in the complete damage state were modeled by the envelope bound convex model, and the bounds of exceeding probability of earthquake loss were obtained by the hybrid earthquake loss model. The loss results of a hotel indicate that non-collapse parts mostly contribute to economic loss, and earthquake loss is more sensitive to repair cost than collapse probability. The presentation form of earthquake loss results is enhanced by the hybrid loss method and is also easier for owners and decision-makers to understand and accept.

Updated seismic hazard assessment of Tunisia

Modern earthquake loss models make use of earthquake catalogs relevant to the seismic hazard assessment upon seismicity and seismotectonic analysis. The main objective of this paper is to investigate a recently compiled catalog (National Institute of Meteorology or INM catalog: 412-2011) and to generate seismic hazard maps through classical probabilistic seismic hazard assessment (PSHA) and smoothed-gridded seismicity models for Tunisia. It is now established with the local earthquake bulletin that the recent seismicity of Tunisia is sparse and moderate. Therefore, efforts must be undertaken to elaborate a robust hazard analysis for risk assessment and seismic design purposes. These recommendations follow the recently published reports by the World Bank that describe the seismic risk in Tunis City as being beyond a tolerable level with an MSK intensity level of VII. Some attempts were made during the past two decades to assess the seismic hazard for Tunisia and they have mostly failed to properly investigate the historical and instrumental seismicity catalog. This limitation also exists for the key aspect of epistemic and random uncertainties impact on the final seismic hazard assessment. This study also investigates new ground motion prediction equations suitable for use in Tunisia. The methodology applied herein uses, for the first time in PSHA of Tunisia, seismicity parameters integrated in logic tree framework to capture epistemic uncertainties through three different seismic source models. It also makes use of the recently released version of OpenQuake engine; an open-source tool for seismic hazard and risk assessment developed in the framework of the Global Earthquake Model.

Evaluation of a recently proposed record selection and scaling procedure for low‐rise to mid‐rise reinforced concrete buildings and its use for probabilistic risk assessment studies

SUMMARYThis paper evaluates a recent record selection and scaling procedure of the authors that can determine the probabilistic structural response of buildings behaving either in the elastic or post‐elastic range. This feature marks a significant strength on the procedure as the probabilistic structural response distribution conveys important information on probability‐based damage assessment. The paper presents case studies that show the utilization of the proposed record selection and scaling procedure as a tool for the estimation of damage states and derivation of site‐specific and region‐specific fragility functions. The method can be used to describe exceedance probabilities of damage limits under a certain target hazard level with known annual exceedance rate (via probabilistic seismic hazard assessment). Thus, the resulting fragility models can relate the seismicity of the region (or a site) with the resulting building performance in a more accurate manner. Under this context, this simple and computationally efficient record selection and scaling procedure can be benefitted significantly by probability‐based risk assessment methods that have started to be considered as indispensable for developing robust earthquake loss models. Copyright © 2013 John Wiley & Sons, Ltd.