ArticlePublisher preview available

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

Springer Nature
Bulletin of Earthquake Engineering
Authors:
Jamal Dabbeek at Eucentre, An-Najah National University
Jamal Dabbeek
  • Eucentre, An-Najah National University
Helen Crowley at Global Earthquake Model (GEM) Foundation
Helen Crowley
  • Global Earthquake Model (GEM) Foundation
Vitor Silva at GEM, EUCENTRE, University of Aveiro
Vitor Silva
  • GEM, EUCENTRE, University of Aveiro
Graeme Weatherill at Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
Graeme Weatherill
Show all 6 authorsHide
Read publisher preview
Download citation
To read the full-text of this research, you can request a copy directly from the authors.

Abstract and Figures

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.
Figures - available from: Bulletin of Earthquake Engineering
This content is subject to copyright. Terms and conditions apply.
A preview of this full-text is provided by Springer Nature.
Learn more
Content available from Bulletin of Earthquake Engineering 
This content is subject to copyright. Terms and conditions apply.
Vol.:(0123456789)
Bulletin of Earthquake Engineering (2021) 19:5819–5841
https://doi.org/10.1007/s10518-021-01194-x
1 3
ORIGINAL ARTICLE
Impact ofexposure spatial resolution onseismic loss
estimates inregional portfolios
JamalDabbeek1,2 · HelenCrowley1 · VitorSilva3,4 · GraemeWeatherill5 ·
NicolePaul3· CeciliaI.Nievas5
Received: 2 April 2021 / Accepted: 30 July 2021 / Published online: 9 August 2021
© The Author(s), under exclusive licence to Springer Nature B.V. 2021
Abstract
The spatial resolution of exposure data has a substantial impact on the accuracy and reli-
ability 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 loca-
tions and site properties using a density map of the built areas can improve the accuracy of
the estimated losses.
Keywords Exposure resolution· Site effects· Seismic risk· Europe
1 Introduction
A common issue in earthquake risk models is related to whether the resolution of the
exposure data is sufficiently detailed. The exposure information available from pub-
lic resources is typically aggregated with limited information about the actual spatial
* Jamal Dabbeek
Jamal.aldabbeek@eucentre.it
1 EUCENTRE, Pavia, Italy
2 Faculty ofEngineering andInformation Technology, An-Najah National University, Nablus,
Palestine
3 GEM Foundation, Pavia, Italy
4 Faculty ofScience andTechnology, University Fernando Pessoa, Porto, Portugal
5 GFZ German Research Centre forGeosciences, Potsdam, Germany
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Over the years, this topic continued to attract attention as researchers (DeBock and Liel 2015;Gomez-Zapata et al. 2021;Kalakonas et al. 2020;Mistry and Lombardi 2023;Pittore et al. 2020;Käser 2018, 2020;Fayjaloun et al. 2021) sought to understand the effects of location uncertainty and/or exposure aggregation, and devise strategies to minimize them. Perhaps the most comprehensive study on the effects of exposure aggregation to date comes from Dabbeek et al. (2021). The latter performed a large-scale sensitivity analysis in the context of the European Seismic Risk Model 2020, (ESRM20; Crowley et al. 2021) exploring the impact of exposure resolution and aggregation strategy, while looking at results at different scales. ...
... These two approximations, generally, do not affect average loss estimates (e.g. AAL), but distort the loss distribution, reducing loss estimates associated with high probabilities (or low return periods) and increasing those associated with low probabilities (or long return periods; Bazzurro and Park 2007;Dabbeek et al. 2021). ...
Exposure manipulation strategies for balancing computational efficiency and precision in seismic risk analysis
Article
Full-text available
Exposure models for regional seismic risk assessment often place assets at the centroids of administrative units for which data are available. At best, a top-down approach is followed, where such data are spatially disaggregated over a denser spatial grid, using proxy datasets such as the distribution of population or the density of night-time lights. The resolution of the spatial grid is either dictated by the resolution of the proxy dataset, or by constraints in computational resources. On the other hand, if a building-by-building database is available, it often needs to be aggregated and brought to a resolution that ensures acceptable calculation runtimes and memory demands. Several studies have now investigated the impact of exposure aggregation on loss estimates. Herein, unlike previous attempts, we can leverage upon an extensive building-by-building database for the Swiss territory, which we can use as ground truth. We firstly proceed to assess the aggregation-induced errors of standard risk metrics at different spatial scales. Then a new strategy for performing said aggregation is proposed, relying on a K-means clustering of site parameters and a reduction of the loss ratio uncertainty for aggregated assets. These interventions are designed with the objective of minimizing errors, while keeping the computational cost manageable.
View
... The exposure models were developed using the broad steps outlined by Yepes-Estrada et al. (2017): identification of the building classes and mapping the building classes to the census. Finally, the buildings were then spatially distributed on a 500 m grid using population density to enhance the accuracy of the model (Dabbeek et al. 2021). The details for each step are described in the following sections. ...
... The number of houses needs to be distributed spatially to give a more realistic model for the maximum ground motion experienced by each house. It is an accepted methodology to use population models to distribute the houses and this has been shown to increase the accuracy of the model (Dabbeek et al. 2021). In this study we use the ...
Fragility of Indonesian houses: scenario damage analysis of the 2006 Yogyakarta and 2009 Padang earthquakes
Article
Full-text available
Indonesia is located in one of the most seismically active regions in the world and often experiences damaging earthquakes. In the past the housing sector has sustained higher earthquake related damage and losses than other sectors. This is often attributed to the fact that the most common houses in Indonesia are non-engineered, built with poor quality workmanship, poor quality materials and without resilient seismic design features. However little effort has been made to quantify how fragile Indonesian houses are, or how their fragility may vary according to the population density or relative wealth of a region. It is not possible to derive empirical fragility functions for Indonesia due to insufficient damage data. The aim of this study is to determine whether existing earthquake fragility functions can be applied to common house types in Indonesia. Scenario damage analyses simulating the 2006 Yogyakarta and 2009 Padang events were undertaken several times testing different fragility functions. The simulated damage results were then compared to the damage observed post event to determine whether an accurate damage prediction could be achieved. It was found that the common house types in Yogyakarta and Central Java vary according to age of construction, location and relative wealth of a region and can be reasonably well represented by existing fragility functions. However, the houses in Padang and surrounding West Sumatra did not vary in a predictable manner and are more fragile than anticipated. Therefore, the fragility of the most common house types in Indonesia differs between Central Java and West Sumatra. This has important implications for seismic damage and risk assessment undertaken in Indonesia.
View
... For high hazard areas, since the rupture patterns of large earthquakes are more complex, the variation in simulated ground motions is expected to have a large impact on the risk estimation as well, as revealed by studies conducted for Istanbul, Turkey and Thessaloniki, Greece 14,15 . In contrast, when the spatial resolution of the exposure model was changed from 1 km × 1 km to 8 km × 8 km, the difference in the estimated seismic loss was less than 5% 16 . Additionally, studies in the field of earthquake engineering have indicated that the uncertainty in building response is more sensitive to changes in ground shaking than to changes in structural modelling [17][18][19][20] . ...
Can we develop a more targeted approach to mitigating seismic risk?
Article
Full-text available
  • Sep 2024
The recent high death tolls caused by large earthquakes are a further indication that earthquakes remain one of the most destructive natural hazards in the world and can seriously threaten the achievement of disaster reduction goals. To effectively reduce the existing seismic risk, the limited available mitigation resources should be allocated to areas with the most severe potential risk. However, identifying localized concentrations of risk requires detailed studies. Here, we propose a strategy to delineate regional high seismic risk zone at a fine resolution and with high confidence. We demonstrate this strategy by using the seismic hazard and loss estimation results for earthquake scenarios with a magnitude of Mw 7.5 for the Jiaocheng fault of the Shanxi Rift System, China. Our analyses reveal that the delineated zone accounts for only ~7% of the regional land area but for ~85% of the total financial loss. We recommend prioritizing seismic risk mitigation measures in such high-risk zones, especially for densely populated cities in seismically active areas, to better meet the disaster risk reduction targets in the Sendai Framework.
View
... V S30 values are then directly extracted at the coordinates of the entries in the exposure model, i.e. the nine centroids in the BRGM exposure model, the one centroid in the ESRM20 exposure model, or the 327 points in the building-by-building exposure model. The second site model (ESRM20 V S30 ) uses the values of V S30 that are returned for the coordinates of the exposure centroids by the point workflow in the exposure to site tool in ESRM20 (Dabbeek et al., 2021). In the case of the buildingby-building scenario calculations, the V S30 values for the ESRM20 V S30 model are obtained using the exposure to site tool in ESRM20, in which the point workflow is applied, which returns the V S30 value associated with the 30 arcsec cell where the query points are found. ...
Comparing components for seismic risk modelling using data from the 2019 Le Teil (France) earthquake
Article
Full-text available
Probabilistic seismic hazard and risk models are essential to improving our awareness of seismic risk, to its management, and to increasing our resilience against earthquake disasters. These models consist of a series of components, which may be evaluated and validated individually, although evaluating and validating these types of models as a whole is challenging due to the lack of recognized procedures. Estimations made with other models, as well as observations of damage from past earthquakes, lend themselves to evaluating the components used to estimate the severity of damage to buildings. Here, we are using a dataset based on emergency post-seismic assessments made after the Le Teil 2019 earthquake, third-party estimations of macroseismic intensity for this seismic event, shake maps, and scenario damage calculations to compare estimations under different modelling assumptions. First we select a rupture model using estimations of ground motion intensity measures and macroseismic intensity. Subsequently, we use scenario damage calculations based on different exposure models, including the aggregated exposure model in the 2020 European Seismic Risk Model (ESRM20), as well as different site models. Moreover, a building-by-building exposure model is used in scenario calculations, which individually models the buildings in the dataset. Lastly, we compare the results of a semi-empirical approach to the estimations made with the scenario calculations. The post-seismic assessments are converted to EMS-98 (Grünthal, 1998) damage grades and then used to estimate the damage for the entirety of the building stock in Le Teil. In general, the scenario calculations estimate lower probabilities for damage grades 3–4 than the estimations made using the emergency post-seismic assessments. An exposure and fragility model assembled herein leads to probabilities for damage grades 3–5 with small differences from the probabilities based on the ESRM20 exposure and fragility model, while the semi-empirical approach leads to lower probabilities. The comparisons in this paper also help us learn lessons on how to improve future testing. An improvement would be the use of damage observations collected directly on the EMS-98 scale or on the damage scale in ESRM20. Advances in testing may also be made by employing methods that inform us about the damage at the scale of a city, such as remote sensing or data-driven learning methods fed by a large number of low-cost seismological instruments spread over the building stock.
View
... With the ESRM20 requirement of characterising ground motion on the soil surface across all regions of building exposure in Europe, a novel approach was needed to represent the local-scale site amplification in the seismic risk calculations and to propagate the increased uncertainties from the regional-scale approach into the probabilistic assessments of loss. This is explained in detail by Weatherill et al. (2023), and the way the site model is calibrated to represent the most suitable input for the given exposure model is described by Dabbeek et al. (2021). In addition, a brief overview of the whole model can be found in the technical reports released with the ESHM20 (Danciu et al., 2021) and ESRM20 . ...
Modelling seismic ground motion and its uncertainty in different tectonic contexts: challenges and application to the 2020 European Seismic Hazard Model (ESHM20)
Article
Full-text available
Current practice in strong ground motion modelling for probabilistic seismic hazard analysis (PSHA) requires the identification and calibration of empirical models appropriate to the tectonic regimes within the region of application, along with quantification of both their aleatory and epistemic uncertainties. For the development of the 2020 European Seismic Hazard Model (ESHM20) a novel approach for ground motion characterisation was adopted based on the concept of a regionalised scaled-backbone model, wherein a single appropriate ground motion model (GMM) is identified for use in PSHA, to which adjustments or scaling factors are then applied to account for epistemic uncertainty in the underlying seismological properties of the region of interest. While the theory and development of the regionalised scaled-backbone GMM concept have been discussed in earlier publications, implementation in the final ESHM20 required further refinements to the shallow-seismicity GMM in three regions, which were undertaken considering new data and insights gained from the feedback provided by experts in several regions of Europe: France, Portugal and Iceland. Exploration of the geophysical characteristics of these regions and analysis of additional ground motion records prompted recalibrations of the GMM logic tree and/or modifications to the proposed regionalisation. These modifications illustrate how the ESHM20 GMM logic tree can still be refined and adapted to different regions based on new ground motion data and/or expert judgement, without diverging from the proposed regionalised scaled-backbone GMM framework. In addition to the regions of crustal seismicity, the scaled-backbone approach needed to be adapted to earthquakes occurring in Europe's subduction zones and to the Vrancea deep seismogenic source region. Using a novel fuzzy methodology to classify earthquakes according to different seismic regimes within the subduction system, we compare ground motion records from non-crustal earthquakes to existing subduction GMMs and identify a suitable-backbone GMM for application to subduction and deep seismic sources in Europe. The observed ground motion records from moderate- and small-magnitude earthquakes allow us to calibrate the anelastic attenuation of the backbone GMM specifically for the eastern Mediterranean region. Epistemic uncertainty is then calibrated based on the global variability in source and attenuation characteristics of subduction GMMs. With the ESHM20 now completed, we reflect on the lessons learned from implementing this new approach in regional-scale PSHA and highlight where we hope to see new developments and improvements to the characterisation of ground motion in future generations of the European Seismic Hazard Model.
View
Managing Induced Seismicity Risks From Enhanced Geothermal Systems: A Good Practice Guideline
Article
Full-text available
Geothermal energy is a green source of power that could play an important role in climate‐conscious energy portfolios; enhanced geothermal systems (EGS) have the potential to scale up exploitation of thermal resources. During hydraulic fracturing, fluids injected under high‐pressure cause the rock mass to fail, stimulating fractures that improve fluid connectivity. However, this increase of pore fluid pressure can also reactivate pre‐existing fault systems, potentially inducing earthquakes of significant size. Induced earthquakes are a significant concern for EGS operations. In some cases, ground shaking nuisance, building damages, or injuries have spurred the early termination of projects (e.g., Basel, Pohang). On the other hand, EGS operations at Soultz‐sous‐Forêts (France), Helsinki (Finland), Blue Mountain (Nevada, USA), and Utah FORGE (USA) have adequately managed induced earthquake risks. The success of an EGS operation depends on economical reservoir enhancements, while maintaining acceptable seismic risk levels. This requires state‐of‐the‐art seismic risk management. This article reviews domains of seismology, earthquake engineering, risk management, and communication. We then synthesize “good practice” recommendations for evaluating, mitigating, and communicating the risk of induced seismicity. We advocate for a modular approach. Recommendations are provided for key technical aspects including (a) a seismic risk management framework, (b) seismic risk pre‐screening, (c) comprehensive seismic hazard and risk evaluation, (d) traffic light protocol designs, (e) seismic monitoring implementation, and (f) step‐by‐step communication plans. Our recommendations adhere to regulatory best practices, to ensure their general applicability. Our guidelines provide a template for effective earthquake risk management and future research directions.
View
Rapid damage assessment effectiveness for the 2023 Kahramanmaraş Türkiye earthquake sequence
Article
  • Jul 2024
The recent devastating 2023 Türkiye earthquakes underscored the urgent need for an early estimate of quantitative losses following destructive seismic events. This study aims to propose and validate a Rapid Damage Assessment (RDA) methodology based solely on open data and tools, easily and readily available globally immediately after a seismic event. In this context, the 2023 Türkiye earthquakes are used as a case study. For the application of the proposed methodology there are two prerequisites: (1) ground shaking data, herein obtained from the US Geological Survey (USGS) ShakeMap system, and (2) a predictive seismic risk model appropriate for the area of interest, consisting of an exposure and a vulnerability model, derived from the 2020 European Seismic Risk Model (ESRM20). Scenario-type analyses for the two major events, the M7.8 - Pazarcik and the M7.5 – Elbistan earthquake, are performed, and the results are compared with the officially reported damages. The main goal is to assess the accuracy of RDA immediately after an earthquake, and whether and to what extent the RDA results can be improved as the USGS ShakeMaps are updated with the incorporation of additional data, and with disaggregation of the exposure model at a finer resolution. The results indicate that the exposure model's disaggregation reduces the damage estimates' standard deviation. At the same time, the effect of the ShakeMap version is minimized when the complete fault rupture is incorporated into the model. The estimated damages are in good agreement with the officially announced data at large scale, which corroborates the proposed methodology, as well as the adopted components of ESRM20.
View
Drought evaluation using various evapotranspiration models over semi-arid river basins
Article
  • Jul 2024
Multivariate drought indices including various hydrological processes into account can be more valuable under climatic and anthropogenic changes. Standardized Precipitation Evapotranspiration Index (SPEI) and Standardized precipitation Actual Evapotranspiration Index (SPAEI) are the drought indices used to estimate drought index, considering precipitation, and evapotranspiration (ET) into account. Many studies used empirical, machine learning, and process-based model estimates of ET for the calculation of drought indices of SPEI and SPAEI. However, the sensitivity of ET estimates on drought characteristics at the catchment scale is highly complex. The present study aimed to include and analyze the sensitivity of various approaches of empirical (Budyko, Penman–Monteith, Hargreaves, and Turc), modeled (SWAT), and remote sensing (MODIS) in the drought characterization using SPEI and SPAEI. The present methodology was tested on a dry-sub-humid river catchment of India, the Tunga-Bhadra River catchment for the period of 2000–2012. The performance of statistical indicators (Nash–Sutcliffe Efficiency and R2) for SPEI values by various empirical methods of Potential Evapotranspiration (PET) (i) Penman–Monteith (ii) Hargreaves against remote sensing PET were 0.93 and 0.95, respectively, which are high in comparison with SWAT simulated PET-based SPEI values, which shows NSE values of 0.85 against remote sensing PET-based SPEI.
View
Uncertainties in catastrophe modelling: Focus on seismic hazard uncertainty based on ESHM updates
Preprint
Full-text available
  • May 2024
Catastrophe models serve as valuable tools for evaluating and managing the impacts of natural disasters, yet their accuracy is susceptible to inherent uncertainties. This article explores the implications of uncertainty within catastrophe models, with a specific focus on the hazard component. The introductory section, presents an analytical framework for developing the three main components of an earthquake catastrophe model - hazard, vulnerability, and exposure – and discussed the associated uncertainties. The subsequent section underscores the crucial role of sufficient data for accurate risk assessment, highlighting the sensitivity of the estimates to hazard modeling assumptions and structural system properties. It discusses the role of extrapolation techniques in refining hazard curves, together with limitations and challenges. The final section presents a comparative analysis of two versions of the European Seismic Hazard Model (ESHM), ESHM13 vs ESM20, examining the effects of hazard variation on risk outcomes across different locations. Lastly, the paper suggests a simplified method to model future updates of the hazard model, assessing the potential implications on RM estimates for different structural systems.
View
Investigating the sensitivity of losses to time-dependent components of seismic risk modeling
Article
  • Feb 2024
Conventional earthquake risk modeling involves several notable simplifications, which neglect: (1) the effects on seismicity of interactions between adjacent faults and the long-term elastic rebound behavior of faults; (2) short-term hazard increases associated with aftershocks; and (3) the accumulation of damage in assets due to the occurrence of multiple earthquakes in a short time window, without repairs. Several recent earthquake events (e.g. 2010–2011 Canterbury earthquakes, New Zealand; 2019 Ridgecrest earthquakes, USA; and 2023 Turkey–Syria earthquakes) have emphasized the need for risk models to account for the aforementioned short- and long-term time-dependent characteristics of earthquake risk. This study specifically investigates the sensitivity of monetary loss (i.e. a possible earthquake-risk-model output) to these time dependencies, for a case-study portfolio in Central Italy. The investigation is intended to provide important insights for the catastrophe risk insurance and reinsurance industry. In addition to salient catastrophe risk insurance features, the end-to-end approach for time-dependent earthquake risk modeling used in this study incorporates recent updates in long-term time-dependent fault modeling, aftershock forecasting, and vulnerability modeling that accounts for damage accumulation. The sensitivity analysis approach presented may provide valuable guidance on the importance and appropriate treatment of time dependencies in regional (i.e. portfolio) earthquake risk models. We find that the long-term fault and aftershock occurrence models are the most crucial features of a time-dependent seismic risk model to constrain, at least for the monetary loss metrics examined in this study. Accounting for damage accumulation is also found to be important, if there is a high insurance deductible associated with portfolio assets.
View
A Building Classification System for Multi-hazard Risk Assessment
Article
Full-text available
  • Feb 2022
A uniform and comprehensive classification system, often referred to as taxonomy, is fundamental for the characterization of building portfolios for natural hazard risk assessment. A building taxonomy characterizes assets according to attributes that can influence the likelihood of damage due to the effects of natural hazards. Within the scope of the Global Earthquake Model (GEM) initiative, a building taxonomy (GEM Building Taxonomy V2.0) was developed with the goal of classifying buildings according to their seismic vulnerability. This taxonomy contained 13 building attributes, including the main material of construction, lateral load-resisting system, date of construction and number of stories. Since its release in 2012, the taxonomy has been used by hundreds of experts working on exposure and risk modeling efforts. These applications allowed the identification of several limitations , which led to the improvement and expansion of this taxonomy into a new classification system compatible with multi-hazard risk assessment. This expanded taxonomy (named GED4ALL) includes more attributes and several details relevant for buildings exposed to natural hazards beyond earthquakes. GED4ALL has been applied in several international initiatives, enabling the identification of the most common building classes in the world, and facilitating compatibility between exposure models and databases of vulnerability and damage databases.
View
View
Sensitivity of Earthquake Damage Estimation to the Input Data (Soil Characterization Maps and Building Exposure): Case Study in the Luchon Valley, France
Article
Full-text available
  • Jun 2021
This article studies the effects of the soil data and exposure data of residential building inventories, as well as their spatial resolution, on seismic damage and loss estimates for a given earthquake scenario. Our aim is to investigate how beneficial it would be to acquire higher resolution inventories at the cost of additional effort and resources. Seismic damage computations are used to evaluate the relative influence of varying spatial resolution on a given damage model, where other parameters were held constant. We use soil characterization maps and building exposure inventories, provided at different scales from different sources: the European database, a national dataset at the municipality scale, and local field investigations. Soil characteristics are used to evaluate site effects and to assign amplification factors to the strong motion applied to the exposed areas. Exposure datasets are used to assign vulnerability indices to sets of buildings, from which a damage distribution is produced (based on the applied seismic intensity). The different spatial resolutions are benchmarked in a case-study area which is subject to moderate-to-average seismicity levels (Luchon valley in the Pyrénées, France). It was found that the proportion of heavily damaged buildings is underestimated when using the European soil map and the European building database, while the more refined databases (national/regional vs. local maps) result in similar estimates for moderate earthquake scenarios. Finally, we highlight the importance of pooling open access data from different sources, but caution the challenges of combining different datasets, especially depending on the type of application that is pursued (e.g., for risk mitigation or rapid response tools).
View
Variable resolution probabilistic modeling of residential exposure and vulnerability for risk applications
Article
Full-text available
  • Sep 2020
In risk assessment, the exposure component describes the elements exposed to the natural hazards and susceptible to damage or loss, while the vulnerability component defines the likelihood to incur damage or loss conditional on a given level of hazard intensity. In this article, we propose a novel adaptive approach to exposure modeling which exploits Dirichlet-Multinomial Bayesian updating to implement the incremental assimilation of sparse in situ survey data into probabilistic models described by compositions (proportions). This methodology is complemented by the introduction of a custom spatial aggregation support based on variable-resolution Central Voronoidal Tessellations. The proposed methodology allows for a more consistent integration of empirical observations, typically from engineering surveys, into large-scale models that can also efficiently exploit expert-elicited knowledge. The resulting models are described in a probabilistic framework, and as such allow for a more thorough analysis of the underlying uncertainty. The proposed approach is applied and discussed in five countries in Central Asia.
View
A ground motion logic tree for seismic hazard analysis in the stable cratonic region of Europe: regionalisation, model selection and development of a scaled backbone approach
Article
Full-text available
Regions of low seismicity present a particular challenge for probabilistic seismic hazard analysis when identifying suitable ground motion models (GMMs) and quantifying their epistemic uncertainty. The 2020 European Seismic Hazard Model adopts a scaled backbone approach to characterise this uncertainty for shallow seismicity in Europe, incorporating region-to-region source and attenuation variability based on European strong motion data. This approach, however, may not be suited to stable cratonic region of northeastern Europe (encompassing Finland, Sweden and the Baltic countries), where exploration of various global geophysical datasets reveals that its crustal properties are distinctly different from the rest of Europe, and are instead more closely represented by those of the Central and Eastern United States. Building upon the suite of models developed by the recent NGA East project, we construct a new scaled backbone ground motion model and calibrate its corresponding epistemic uncertainties. The resulting logic tree is shown to provide comparable hazard outcomes to the epistemic uncertainty modelling strategy adopted for the Eastern United States, despite the different approaches taken. Comparison with previous GMM selections for northeastern Europe, however, highlights key differences in short period accelerations resulting from new assumptions regarding the characteristics of the reference rock and its influence on site amplification.
View
A regionally-adaptable “scaled backbone” ground motion logic tree for shallow seismicity in Europe: application to the 2020 European seismic hazard model
Article
Full-text available
The selection of ground motion models, and the representation of their epistemic uncertainty in the form of a logic tree, is one of the fundamental components of probabilistic seismic hazard and risk analysis. A new ground motion model (GMM) logic tree has been developed for the 2020 European seismic hazard model, which develops upon recently compiled ground motion data sets in Europe. In contrast to previous European seismic hazard models, the new ground model logic tree is built around the scaled backbone concept. Epistemic uncertainties are represented as calibrations to a reference model and aim to characterise the potential distributions of median ground motions resulting from variability in source scaling and attenuation. These scaled backbone logic trees are developed and presented for shallow crustal seismic sources in Europe. Using the new European strong motion flatfile, and capitalising on recent perspectives in ground motion modelling in the scientific literature, a general and transferable procedure is presented for the construction of a backbone model and the regionalisation of epistemic uncertainty. This innovative approach forms a general framework for revising and updating the GMM logic tree at national and European scale as new strong motion data emerge in the future.
View
Development of a fragility and vulnerability model for global seismic risk analyses
Article
Full-text available
Seismic fragility and vulnerability assessment is an essential step in the evaluation of probabilistic seismic risk. Ideally, models developed and calibrated for the building portfolio of interest would be readily available. However, the lack of damage data and insufficient analytical studies lead to a paucity of fragility and vulnerability models, in particular in the developing world. This study describes the development of an analytical fragility and vulnerability model covering the most common building classes at the global scale. Nearly five hundred functions were developed to cover the majority of combinations of construction material, height, lateral load resisting system and seismic design level. The fragility and vulnerability were derived using nonlinear time-history analyses on equivalent single-degree-of-freedom oscillators and a large set of ground motion records representing several tectonic environments. The resulting fragility and vulnerability functions were validated through a series of tests which include the calculation of the average annual loss ratio for a number of locations, the comparison of probabilities of collapse across all building classes, and the repetition of past seismic events. The set of vulnerability functions was used for the assessment of economic losses due to earthquakes as part of the global seismic risk model supported by the Global Earthquake Model Foundation. (full-text viewer available at: https://rdcu.be/b4Kal)
View
A regionally-adaptable ground-motion model for shallow crustal earthquakes in Europe
Article
Full-text available
To complement the new European Strong-Motion dataset and the ongoing efforts to update the seismic hazard and risk assessment of Europe and Mediterranean regions, we propose a new regionally adaptable ground-motion model (GMM). We present here the GMM capable of predicting the 5% damped RotD50 of PGA, PGV, and SA(T = 0.01 − 8 s) from shallow crustal earthquakes of 3 ≤ MW ≤ 7.4 occurring 0 < RJB ≤ 545 km away from sites with 90 ≤ Vs30 ≤ 3000 m s−1 or 0.001 ≤ slope ≤ 1 m m−1. The extended applicability derived from thousands of new recordings, however, comes with an apparent increase in the aleatory variability (σ). Firstly, anticipating contaminations and peculiarities in the dataset, we employed robust mixed-effect regressions to down weigh only, and not eliminate entirely, the influence of outliers on the GMM median and σ. Secondly, we regionalised the attenuating path and localised the earthquake sources using the most recent models, to quantify region-specific anelastic attenuation and locality-specific earthquake characteristics as random-effects, respectively. Thirdly, using the mixed-effect variance– covariance structure, the GMM can be adapted to new regions, localities, and sites with specific datasets. Consequently, the σ is curtailed to a 7% increase at T < 0.3 s, and a substantial 15% decrease at T ≥ 0.3 s, compared to the RESORCE based partially non-ergodic GMM. We provide the 46 attenuating region-, 56 earthquake localities-, and 1829 site-specific adjustments, demonstrate their usage, and present their robustness through a 10-fold cross-validation exercise. Open-access: https://rdcu.be/b4kWx
View
Exposure model for European seismic risk assessment
Article
  • Jun 2020
Building exposure and vulnerability models for seismic risk assessment have been the focus of a number of European projects in recent years, but there has never been a concerted effort among the research community to produce a uniform European risk model. The European Commission’s Horizon 2020 SERA project has a work package that is dedicated to that objective, through the development of an exposure model, an associated set of fragility/vulnerability models, and a database of socioeconomic indicators in order to calculate probabilistic integrated seismic risk at a European scale. This article provides details of the development of the first versions of the European exposure model that describe the distribution of the main residential, industrial and commercial building classes across all countries in Europe, as well as their occupants and replacement costs. The v0.1 of the European exposure model has been integrated within the Global Earthquake Model’s global exposure and risk maps. Preliminary analyses using the model show that almost 35% of the residential population in Europe is exposed to a 475-year return period peak ground acceleration (PGA) hazard of at least 0.1 g, thus highlighting the importance of European seismic risk modeling and mitigation.
View
View