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Calibrating collapse and fatality rates for the assessment of fatalities due to earthquakes
Abstract
In recent decades, hundreds of studies have covered seismic vulnerability assessment and the derivation of fragility models. However, these studies primarily focus on structural damage and the associated repair costs. Assessing fatalities requires an evaluation of the proportion of damaged buildings that suffer partial or total collapse, as well as the expected fatality rates for occupants inside those collapsed buildings. To support these modeling needs, we reviewed past studies on casualties, existing proposals for collapse and fatality rates, and detailed damage databases that characterize different collapse mechanisms. Based on this review, collapse and fatality rates are proposed relative to a baseline building class. These rates are further calibrated considering reported fatalities since 1950 and the average annual fatalities estimated by the Global Seismic Risk Model of the Global Earthquake Model (GEM) Foundation. Results show that the probability of collapse tends to decrease with the number of stories, while fatality rates have the opposite trend. Furthermore, an open-access database of calibrated collapse and fatality rates is provided and can be used to assess fatalities due to earthquake scenarios or in probabilistic seismic risk analysis.
The estimation of road disruptions due to building debris in urban contexts requires the availability of exposure data at the building level, which is often not available. In this study, we explore how open global datasets at different scales can be integrated with machine learning algorithms to estimate road disruptions following seismic events, overcoming the need for detailed datasets. Using simulated impact data for the municipality of Lisbon, we train a Random Forest model to predict road disruptions due to building collapses. Then, we apply this model to another urban environment (the municipality of Amadora) to evaluate the performance of the model using input data unseen during the training process. Finally, we employ the surrogate model using information extracted from globally available datasets characterizing the built environment and the road network. The proposed approach allows identifying areas within urban centers where road disruptions are likely to occur, and where risk reduction measures should be prioritized to minimize the impact of destructive earthquakes.
This study aims to compare the collapse probability of reinforced concrete infilled frames designed in accordance with modern Indian seismic codes. Multiple versions of bare and infilled (both fully and partially) frames are considered. A total of 33 frames are divided into eight sets based on the parameter being varied, namely, the quality and thickness of infills, design code, aspect ratio, and number of stories. The collapse probability is evaluated through multiple stripe analysis with eight stripes corresponding to different return periods. A set of 40 ground motions, consistent with the site-specific uniform hazard spectra corresponding to each return period, is selected. Results suggest that the frames designed for pre-2016 Indian codes perform considerably worse than those designed for post-2016 Indian codes, which are on par with other national codes. The effect of collapse probability of addition of infills to bare frames is found to be negligible to significantly negative depending on factors such as adopted design code, relative strength of infill strut to columns, aspect ratio, and number of stories. Four-story frames perform worse than 8-story frames. Interestingly, the 8-story open first story frames, designed for modern codes, are not found to be significantly more vulnerable than their fully infilled counterparts.
We have compiled a new catalogue of earthquake fatalities for the world, covering the period 856 BC to March 2022, listing 2795 reports. We estimate that the reporting of fatal earthquakes is complete for events with more than 16 fatalities since 1927. The total number of fatalities recorded is 8,336,526. 117 countries have reported at least one earthquake with one fatality or more. 77 and 52 countries have reported more than 100 and 1000 earthquake fatalities, respectively. Caution has to be exercised in estimating what earthquake disasters are in store for a given country because the 95 year period of high quality recording is about an order of magnitude shorter than return times of great earthquakes. Nevertheless, we introduce the earthquake potency for a country, defined as the sum of recorded fatalities divided by the number of earthquakes that it took to accumulate them, which equals the average earthquake disaster size in a given country, in units of fatalities per event. Potency is listed based on all known fatal earthquakes and also based on those since 1927. Both lists have their shortcomings, but provide estimates of what size of future earthquake disaster is likely in store for a particular country. For rescue purposes, it is important to realize that small earthquake, M 5 ± 0.5, can cause significant numbers of fatalities.
Adobe construction represents 5.3% of the total Portuguese building stock according to the latest National Housing Census. The distribution of these adobe buildings is scattered across the country, with higher density in the central region and in Algarve in the south, where the seismic hazard is highest. A large proportion of these buildings are still in use for residential and commercial purposes and are of historical significance, contributing to the cultural heritage of the country. Adobe buildings are known to exhibit low seismic resistance due to their brittle behavior, thus making them vulnerable to ground shaking and more prone to structural damage that can potentially cause human fatalities. Three buildings with one-story, two-stories, and two-stories plus an attic were numerically modeled using solid and contact elements. Calibration and validation of material properties were carried out following experimental results. A set of 30 ground motion records with bi-directional components were selected, and non-linear time-history analyses were performed until complete collapse occurred. Two novel engineering demand parameters (EDPs) were used, and damage thresholds were proposed. Finally, fragility and fatality vulnerability functions were derived. These functions can be used directly in seismic risk assessment studies.
As part of the development of a European Seismic Risk Model 2020 (ESRM20), the spatial and temporal evolution of seismic design across Europe has been studied in order to better classify reinforced concrete buildings (which represent more than 30% of the approximately 145 million residential, commercial and industrial buildings in Europe) and map them to vulnerability models based on simulated seismic design. This paper summarises the model that has been developed to assign the years when different seismic design levels (low code, moderate code and high code) were introduced in a number of European countries and the associated lateral forces that were specified spatially within each country for the low and moderate codes for typical reinforced concrete mid-rise buildings. This process has led to an improved understanding of how design regulations evolved across Europe and how this has impacted the vulnerability of the European residential building stock. The model estimates that ~ 60% of the reinforced concrete buildings in Europe have been seismically designed, and of those buildings ~ 60% have been designed to low code, ~ 25% to moderate code and 15% to high code. This seismic design model aims at being a dynamic source of information that will be continuously updated with additional feedback from local experts and datasets. To this end, all of the data has been made openly available as shapefiles on a GitLab repository.
In this article, we present a new data collection that combines information about earthquake damage with seismic shaking. Starting from the Da.D.O. database, which provides information on the damage of individual buildings subjected to sequences of past earthquakes in Italy, we have generated ShakeMaps for all the events with magnitude greater than 5.0 that have contributed to these sequences. The sequences under examination are those of Irpinia 1980, Umbria Marche 1997, Pollino 1998, Molise 2002, L’Aquila 2009 and Emilia 2012. In this way, we were able to combine, for a total of the 117,695 buildings, the engineering parameters included in Da.D.O., but revised and reprocessed in this application, and the ground shaking data for six different variables (namely, intensity in MCS scale, PGA, PGV, SA at 0.3s, 1.0s and 3.0s). The potential applications of this data collection are innumerable: from recalibrating fragility curves to training machine learning models to quantifying earthquake damage. This data collection will be made available within Da.D.O., a platform of the Italian Department of Civil Protection, developed by EUCENTRE.
The development of seismic fragility functions for buildings generally relies on simplified modelling methods and the use of indirect engineering demand parameters (EDPs) for the determination of collapse or other damage states. The collapse response of real buildings, particularly those that have not been specifically designed for seismic resistance, can often be driven by local failures that may not be captured in simplified models. Furthermore, the use of EDP thresholds to indicate damage states may not be consistent with multiple possible failure modes, which may be triggered by different characteristics of the ground shaking or variations in model parameters. This paper demonstrates the use of non-linear finite element models including explicit progressive collapse simulation for the development of fragility functions. It presents an overview of the method developed and its application to an unreinforced masonry (URM) building typology in the Groningen region of the Netherlands, where induced seismicity risk is currently being evaluated. Multiple index buildings were selected to represent the variations in geometry, material properties, and connection types found within the typology. For each index building, Latin Hypercube sampling was used to generate batches of several hundred realisations of an LS-DYNA time-history analysis, each selecting from a set of 100 hazard-consistent ground motions, and varying material properties and other uncertain variables according to pre-assigned probability distributions. Automation was used in model generation, running analyses and in post-processing to allow the required computation with minimal analyst intervention. The main output from each analysis was a normalised debris cover estimate, which describes the extent of damage observed in the model and is correlated with life safety risk. Regression analyses were carried out directly on threshold levels of debris cover identified building collapse. Fragility functions were developed for the URM terraced house typology by combining results from the individual index buildings together.
This study presents a seismic risk assessment and a set of earthquake scenarios for the residential building stock of the three largest metropolitan centers of Colombia: Bogotá, Medellín and Cali (with 8.0, 2.5, and 2.4 million inhabitants, respectively). A uniform methodology was followed for the development of the seismic hazard, vulnerability, and exposure models, thus allowing a direct comparison between the seismic risk of the different cities. Risk metrics such as exceedance probability curves and average annual losses were computed for each city. The earthquake scenarios were selected considering events whose direct economic impact is similar to the aggregated loss for a probability of exceedance of 10% in 50 years. Results show a higher mean aggregate loss ratio for Cali and similar mean aggregate loss ratios for Bogotá and Medellín. All of the models used in this study are openly accessible, enabling risk modelers, engineers, and stakeholders to explore them for disaster risk management.
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.
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Building volume loss can be directly correlated with earthquake fatalities and is therefore considered to be a better damage descriptor for estimating risk to occupants than traditional damage states. Empirical volume loss studies are limited and the study presented herein represents what is likely the first attempt to develop a relationship between commercial unreinforced brick masonry (URBM) buildings attributes, ground motion, and fatalities based on empirical data. Data from two New Zealand earthquakes was utilized to develop a model that predicts the probability of a URBM buildings being in a volume loss damage states (VDS) and the associated probability of an occupant fatality. To demonstrate application of the model, two New Zealand earthquake scenarios are presented and discussed. The model is intended to be applied at a broad scale, to capture an average response over a large number of New Zealand URBM buildings, with applicability to other countries having stocks of comparable URBM buildings.
Since 2015, the Global Earthquake Model (GEM) Foundation and its partners have been supporting regional programs and bilateral collaborations to develop an open global earthquake risk model. These efforts led to the development of a repository of probabilistic seismic hazard models, a global exposure dataset comprising structural and occupancy information regarding the residential, commercial and industrial buildings, and a comprehensive set of fragility and vulnerability functions for the most common building classes. These components were used to estimate probabilistic earthquake risk globally using the OpenQuake-engine, an open-source software for seismic hazard and risk analysis. This model allows estimating a number of risk metrics such as annualized average losses or aggregated losses for particular return periods, which are fundamental to the development and implementation of earthquake risk mitigation measures.
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.
Significance
High death tolls from recent earthquakes have highlighted the need to better identify ways to effectively reduce seismic risk. We address this need by developing a new earthquake scenario ensemble approach. We model impacts from multiple different earthquake scenarios, identifying impacts that are common to multiple scenarios. This method allows us to estimate whether particular impacts are specific to certain earthquakes or occur irrespective of the location or magnitude of the next earthquake. Our method provides contingency planners with critical information on the likelihood, and probable scale, of impacts in future earthquakes, especially in situations where robust information on the likelihood of future earthquakes is incomplete, allowing disaster risk-reduction efforts to focus on minimizing such effects and reducing seismic risk.
In this study, loss estimation models were developed for reasonably accurate assessment of economic and human losses from seismic events in the Mediterranean region, based on damage assessment at an urban scale. Data were compiled from existing worldwide databases, and completed with earthquake information from regional studies. Economic data were converted to a single common currency unit (2015 USD value) and the wealth of the areas affected by 65 earthquakes of the region from 1900 to 2015 was assessed. Reduced-form models were used to determine economic and human losses, with earthquake magnitude and intensity as hazard-related variables, and gross domestic product of the affected area and the affected population as exposure-related variables. Damage to buildings was also used as a hazard-related variable to predict economic and human losses. Finally, site-specific regression models were proposed for economic and human losses due to earthquakes in the Mediterranean region, and more specifically, in Algeria. We show that by introducing the damage variable into the models, prediction error can be reduced, and that accuracy of loss model estimation is site dependent and requires regional data on earthquake losses to improve. A case study for Constantine, Algeria shows the improvements needed for increased accuracy.
For the estimation of "local personal risk," i.e., the annual probability of fatality for a hypothetical person continuously present in or near a building, an analyticalmethodology based on the probability of partial and complete collapse mechanisms (fragility models) and the probability of death given those collapse mechanisms (consequence models) for a building stock exposed to induced seismicity ground shaking is presented.
This study presents an open and transparent exposure model for the residential building stock in South America. This model captures the geographical distribution, structural characteristics (including information about construction materials, lateral load resisting system, range of number of stories), average built-up area, replacement cost, expected number of occupants, and number of dwellings and buildings. The methodology utilized to develop this model was based on national population and housing statistics and expert judgment from dozens of local researchers and practitioners. This model has been developed as part of the South America Risk Assessment (SARA) project led by the Global Earthquake Model (GEM), and it can be used to perform earthquake risk analyses. It is available at different geographical scales for seven Andean countries: Argentina, Bolivia, Chile, Colombia, Ecuador, Peru, and Venezuela.
The past devastating earthquakes in densely populated urban centers, such as the 1994 Northridge; 1995 Kobe; 1999 series of Kocaeli, Düzce, and Athens; and 2011 Van-Erciş events, showed that substantial social and economic losses can be expected. Previous studies indicate that inadequate emergency response can increase the number of casualties by a maximum factor of 10, which suggests the need for research on rapid earthquake shaking damage and loss estimation. The reduction in casualties in urban areas immediately following an earthquake can be improved if the location and severity of damages can be rapidly assessed by information from rapid response systems. In this context, a research project (TUBITAK-109M734) titled “Real-time Information of Earthquake Shaking, Damage, and Losses for Target Cities of Thessaloniki and Istanbul” was conducted during 2011–2014 to establish the rapid estimation of ground motion shaking and related earthquake damages and casualties for the target cities. In the present study, application to Istanbul metropolitan area is presented. In order to fulfill this objective, earthquake hazard and risk assessment methodology known as Earthquake Loss Estimation Routine, which was developed for the Euro-Mediterranean region within the Network of Research Infrastructures for European Seismology EC-FP6 project, was used. The current application to the Istanbul metropolitan area provides real-time ground motion information obtained by strong motion stations distributed throughout the densely populated areas of the city. According to this ground motion information, building damage estimation is computed by using grid-based building inventory, and the related loss is then estimated. Through this application, the rapidly estimated information enables public and private emergency management authorities to take action and allocate and prioritize resources to minimize the casualties in urban areas during immediate post-earthquake periods. Moreover, it is expected that during an earthquake, rapid information of ground shaking, damage, and loss estimations will provide vital information to allow appropriate emergency agencies to take immediate action, which will help to save lives. In general terms, this study can be considered as an example for application to metropolitan areas under seismic risk.
Keywords
Rapid response Loss estimation and mapping Shakemaps Damage estimation Real-time information Istanbul city
One essential piece of information used to estimate earthquake casualties is the spatiotemporal distribution of the population. HAZUS-MH is a loss-estimation model nested in a geographic information system that has been developed and freely distributed by the US Federal Emergency Management Agency to estimate loss and damage due to natural hazards. Because inventories of behavioral patterns based on empirical data have not been developed and have relied solely on behavioral information about the US population, they may not provide reliable and meaningful casualty estimations in an international setting. To estimate accurate hourly exposure for an earthquake using empirical data, the study uses a daily time-use survey conducted by Statistics of Korea. The survey contains behavioral data from approximately 21,000 respondents, collected over 24 h. By combining structural damage estimates, calculated by HAZUS-MH, with spatiotemporal behavior patterns estimated using a daily time-behavioral survey in Korea, the study shows the estimated casualties related to a given earthquake scenario in the Ulsan area. The simulation results show that the greatest number of estimated casualties occurred when the earthquake struck between 2 a.m., and 4 a.m. The fewest casualties were expected when the earthquake occurred between 12 p.m., and 2 p.m. The proportion of the indoor population in damaged buildings and the spatial distribution of occupancy type was one of the important factors. During the daytime, casualties increased where the nonresidential occupancy was concentrated. At nighttime, a higher number of casualties were estimated in residential occupancy.
Iran is located in a highly seismic active region and building structures, therefore need to be designed and constructed to withstand major earthquakes. Structural mitigation measures are now seen as one key element to reduce economic as well as human losses for today and in the future. However, the costs and benefits of various options are difficult to be assessed and usually done without considering both human and economic aspects. This paper should fill part of this gap and performs an in-depth earthquake risk analysis for Shiraz city, in Iran. Additionally, the effects of different mitigation measures for buildings and corresponding changes in risk levels have been investigated. Probabilistic seismic hazard analysis is used to prepare the hazard curves, to be used in the probabilistic cost-benefit analysis of buildings to investigate the effects of using different strengthening strategies. Regarding the importance of the assessment of human casualties during earthquakes, additional cost-benefit ratios were calculated by considering the value of statistical life and performing sensitivity analysis. The results show that considering the value of statistical life in cost-benefit analysis can significantly increase the structural cost-benefit ratios. This has important implications for the decision support as well as policy making side in Iran and we conclude with suggestions how these issues could be addressed in the future using a risk-layering approach.
Keywords: Earthquake risk, Probabilistic seismic hazard analysis, Cost-benefit analysis, Human loss, Value of statistical life, Shiraz, Iran.
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Central Asia is one of the seismically most active regions in the world.
Its complex seismicity due to the collision of the Eurasian and Indian
plates has resulted in some of the world’s largest intra-plate events over
history. The region is dominated by reverse faulting over strike slip and
normal faulting events. The GSHAP project (1999), aiming at a hazard
assessment on a global scale, indicated that the region of Central Asia
is characterized by peak ground accelerations for 10% probability of
exceedance in 50 years as high as 9 m/s2. In this study, carried out within
the framework of the EMCA project (Earthquake Model Central Asia),
the area source model and different kernel approaches are used for a
probabilistic seismic hazard assessment (PSHA) for Central Asia. The
seismic hazard is assessed considering shallow (depth < 50 km) seismicity
only and employs an updated (with respect to previous projects)
earthquake catalog for the region. The seismic hazard is calculated in
terms of macroseismic intensity (MSK-64), intended to be used for the
seismic risk maps of the region. The hazard maps, shown in terms of
10% probability of exceedance in 50 years, are derived by using the
OpenQuake software [Pagani et al. 2014], which is an open source software
tool developed by the GEM (Global Earthquake Model) foundation.
The maximum hazard observed in the region reaches an intensity
of around 8 in southern Tien Shan for 475 years mean return period.
The maximum hazard estimated for some of the cities in the region,
Bishkek, Dushanbe, Tashkent and Almaty, is between 7 and 8 (7-8),
8.0, 7.0 and 8.0 macroseismic Intensity, respectively, for 475 years mean
return period, using different approaches. The results of different methods
for assessing the level of seismic hazard are compared and their underlying
methodologies are discussed.
Online material : Data files for seismogenic source zones (polygons), smoothed-gridded seismicity models, and hazard curves at 0.2° regular grid spacing over the study region.
Earthquake disasters occur mainly due to the collapse of buildings and structures triggered by ground motions. It is, therefore, important to predict ground-shaking levels in order to determine appropriate building code provisions for earthquake-resistant design of structures. This involves extensive analyses and development of appropriate seismological models; namely, seismogenic sources, seismic site conditions, and ground motion predictions. The hazard products, viz . data and maps, constitute important tools for framing public policies toward land-use planning, building regulations, insurance, and emergency preparedness.
View this table:
Table 1
Major Earthquake Casualties during 1900–2008 in India and Adjoining Regions
In India, several events during the last 100 years, as listed in Table 1, indicate that even moderate earthquakes ( MW < 7.0) can cause significant devastation. On one hand, ongoing urbanization and unprecedented population growth have considerably aggravated the prevailing seismic risk. On the other hand, the available seismic hazard maps covering the entire country are about a decade old. Consequently an updated seismic hazard model for the country is imperative and necessitated by new data, recent findings, and methodological improvements. In the present study, we make a case for new probabilistic seismic hazard analysis (PSHA) of India. The fundamental studies have been carried out to deliver the hazard components, including seismogenic source zonation and seismicity modeling in the Indian subcontinent (Thingbaijam and Nath 2011), assessment of site conditions across the country (Nath, Thingbaijam, Adhikari et al. 2011), and a suitability test for the ground-motion prediction equations in the regional context (Nath and Thingbaijam 2011). These components are integrated to deliver a preliminary model consisting of spatial distributions of peak ground acceleration (PGA) and 5%-damped pseudo spectral acceleration (PSA).
Initial attempts at …
The focus of the Hazus earthquake model has
been largely U.S. centric due to a lack of standardized
building-infrastructure data formats applicable elsewhere.
In a combined effort between FEMA Region VIII and the
Universidad de Los Andes, Venezuela, the present study
uses the Hazus 2.1 software to simulate earthquake loss
estimations for Venezuela. Population totals and demographic
distributions were developed using Oak Ridge
National Labs Landscan 2008 population data and the
census 2011 for Venezuela. The accuracy of the model was
further enhanced for Mérida State, located in western
Venezuela, by collecting, incorporating, and developing
region and specific inventories including soil maps, liquefaction
and landslide susceptibility studies, demographic
data, and building inventory information. We used USGS
ShakeMaps scenarios for two potential earthquake events
with peak ground accelerations proposed within Performance
Based Seismic Engineering of Buildings, VISION
2000 recommendations. The region has not witnessed an
earthquake with a magnitude greater than M 7 in the last
120 years. Given the historical record of seismicity and the
seismotectonics in the region, it becomes increasingly
important to understand the potential implications from
moderate to large earthquakes in Mérida State, Venezuela.
The assessment of the seismic risk at a national scale represents an important resource in order to introduce measures that may reduce potential losses due to future earthquakes. This evaluation results from the combination of three components: seismic hazard, structural vulnerability and exposure data. In this study, a review of existing studies focusing on each one of these areas is carried out, and used together with data from the 2011 Building Census in Portugal to compile the required input models for the evaluation of seismic hazard and risk. In order to better characterize the epistemic uncertainty in the calculations, several approaches are considered within a logic tree structure, such as the consideration of different seismic source zonations, the employment of vulnerability functions derived based on various damage criteria and the employment of distinct spatial resolutions in the exposure model. The aim of this paper is thus to provide an overview of the recent developments regarding the different aspects that influence the seismic hazard and risk in Portugal, as well as an up-to-date identification of the regions that are more vulnerable to earthquakes, together with the expected losses for a probability of exceedance of 10 % in 50 years. The results from the present study were obtained through the OpenQuake engine, the open-source software for seismic risk and hazard assessment developed within the global earthquake model (GEM) initiative.
The aim of this study was to develop mathematical models for estimating earthquake casualties such as death, number of injured persons, affected families and total cost of damage. To quantify the direct damages from earthquakes to human beings and properties given the magnitude, intensity, depth of focus, location of epicentre and time duration, the regression models were made. The researchers formulated models through regression analysis using matrices and used ? = 0.01.
The study considered thirty destructive earthquakes that hit the Philippines from the inclusive years 1968 to 2012. Relevant data about these said earthquakes were obtained from Philippine Institute of Volcanology and Seismology. Data on damages and casualties were gathered from the records of National Disaster Risk Reduction and Management Council.
The mathematical models made are as follows:
This study will be of great value in emergency planning, initiating and updating programs for earthquake hazard reductionin the Philippines, which is an earthquake-prone country.
A fully probabilistic seismic risk analysis using a comprehensive approach is conducted for Medellin, the second largest city of Colombia, using a building by building database constructed and complemented from aerial images, considering characteristics such as building use categories, socio-economic levels and replacement values. The seismic hazard used for the analysis corresponds to the most updated study available in the country with the same model that was included in the national building code maps definition. Spectral transfer functions are determined for each of the seismic microzonation zones in order to take into account the dynamic soil response and amplification effects in the risk analysis. Several building types are defined for the city and individual vulnerability functions are assigned to each of them. Risk results are presented in the state of the art metrics such as the loss exceedance curve, probable maximum losses for different return periods, average annual losses and risk maps. The obtained results can be classified by use and socio-economic sectors as well as by structural systems that may help the stakeholders to identify where the risk concentrates.
The objective of this work is to examine the sensitivity of fragility functions to variation in parameters’ values that are related to structural characteristics and the dispersion related to modelling strategies. For the structural characteristics, the parameters considered are concrete and reinforcement steel strength, ductility, floor-to-floor story height, and strength of masonry infill panels. For modelling strategies, the dispersion due to the incompleteness of numerical models, such as ignoring the contribution of infill walls to the structural response, is examined. The sensitivity analysis has been based on 3D nonlinear static analysis. The classes of structures considered are RC buildings designed according to earlier seismic codes, which are in general, characterized by poor quality of material. The result of sensitivity analysis shows that the considered structural characteristics-related parameters were found to have a significant effect on the deformation capacity of the structure, a difference of up-to 100%, for different damage condition level. Regarding the contribution of masonry infill panels, it has been clearly observed that neglecting the shift in behaviour caused by the presence of infill leads to inaccuracy in the derivation of fragility curves (large bias in fragility curves). Bare frame model-based fragility curves trend to underestimate the vulnerability of the structure, comparing with the result from infilled frame model-based fragility curves. The present study was conducted within the framework of the research project “Global Vulnerability Estimation Methods” funded by the Global Earthquake Model (GEM) foundation.
The Global Earthquake Model aims to combine the main features of state-of-the-art science, global collaboration and buy-in, transparency and openness in an initiative to calculate and communicate earthquake risk worldwide. One of the first steps towards this objective has been the open-source development and release of software for seismic hazard and risk assessment called the OpenQuake engine. This software comprises a set of calculators capable of computing human or economic losses for a collection of assets, caused by a given scenario event, or by considering the probability of all possible events that might happen within a region within a certain time span. This paper provides an insight into the current status of the development of this tool and presents a comprehensive description of each calculator, with example results.
This paper summarizes the development of a geographic information system (GIS)‐based regional loss estimation methodology for the United States funded as part of a four‐and‐one‐half year project by the Federal Emergency Management Agency (FEMA) through the National Institute of Building Sciences (NIBS). The methodology incorporates state‐of‐the‐art approaches for: characterizing earth science hazards, including ground shaking, liquefaction, and landsliding; estimating damage and losses to buildings and lifelines; estimating casualties, shelter requirements and economic losses; and data entry to support loss estimates. The history of the methodology development; the methodology's scope, framework, and limitations; supporting GIS software; potential user applications; and future developments are discussed.
The assessment of human losses and injuries due to earthquakes is critical for the development of risk reduction measures. Yet, most vulnerability studies have focused on the derivation of fragility functions for structural damage, neglecting the evaluation of the human impact. In this study, we implemented a fatality vulnerability assessment procedure based on advanced structural modelling , with an application to typical limestone and granite masonry buildings in Portugal. We performed nonlinear time-history analysis on 3D numerical models whose characteristics were sampled from statistical models representing the geometric and mechanical properties of this type of construction. Engineering demand parameters, such as volume of loss and volume of survivable space, were estimated and converted into a fatality rate based on observations from past fatal earthquakes. We compared these vulnerability functions with other proposals from the literature in which conventional fragility functions are directly combined with collapse and fatality rates. Finally, the resulting vulnerability functions were tested for two earthquake scenarios for Portugal. The results from this study indicate that the conventional approach for fatality modelling tends to underestimate human losses for strong ground shaking due to the inability to account for catastrophic structural collapses. The fatality vulnerability functions developed in this work can be directly used in probabilistic seismic risk analysis or the assessment of earthquake scenarios.
The global building exposure model is a mosaic of local and regional models with information regarding the residential, commercial, and industrial building stock at the smallest available administrative division of each country and includes details about the number of buildings, number of occupants, vulnerability characteristics, average built-up area, and average replacement cost. We aimed for a bottom-up approach at the global scale, using national statistics, socio-economic data, and local datasets. This model allows the identification of the most common types of construction worldwide, regions with large fractions of informal construction, and areas prone to earthquakes with a high concentration of population and building stock. The mosaic of exposure models presented herein can be used for the assessment of probabilistic seismic risk and earthquake scenarios. Information at the global, regional, and national levels is available through a public repository ( https://github.com/gem/global_exposure_model ), which will be used to maintain, update and improve the models.
The evaluation of the seismic vulnerability of existing structures for regional risk analysis is characterized by sources of uncertainty due to insufficient data (i.e. epistemic) and sources of variability that cannot be reduced (i.e. aleatory). These sources of uncertainty are particularly important for the evaluation of fragility of masonry structure, whose material and geometric properties can vary considerably even within structures of the same building class. This work investigates the impact of epistemic and aleatory uncertainties in the fragility modelling of masonry buildings, with an application to the Portuguese building stock. The geometrical features of the masonry building stock is considered by gathering information from a set of drawings, including the wall thickness, inter-story height, density of walls, among others. These statistics were used to generate a number of representative buildings, by sampling the geometric and material properties. The seismic demand was represented by a set of ground motion records to cover the span of intensity motions according to the seismic hazard of the zone of study. The structural response of the set of buildings was analysed using block-based FEM technique implemented in the LS-Dyna software. This tool allows modelling structural damage, including explicitly structural collapse. This approach allows assessing not just damage and economic losses, but also potential casualties due to fall of debris. The results of the aforementioned analysis were used to compute fragility curves for damage and fatalities. A set of sampled buildings are tested against each record allowing the analysis of building-to-building variability, and how neglecting them might bias the fragility results.
In December 2018, at the conclusion of its second implementation phase, the Global Earthquake Model (GEM) Foundation released its first version of a map outlining the spatial distribution of seismic hazard at a global scale. The map is the result of an extensive, joint effort combining the results obtained from a collection of probabilistic seismic hazard models, called the GEM Mosaic. Together, the map and the underlying database of models provide an up-to-date view of the earthquake threat globally. In addition, using the Mosaic, a synopsis of the current state-of-practice in modeling probabilistic seismic hazard at national and regional scales is possible. The process adopted for the compilation of the Mosaic adhered to the maximum extent possible to GEM’s principles of collaboration, inclusiveness, transparency, and reproducibility. For each region, priority was given to seismic hazard models either developed by well-recognized national agencies or by large collaborative projects involving local scientists. The version of the GEM Mosaic presented herein contains 30 probabilistic seismic hazard models, 14 of which represent national or sub-national models; the remainder are regional-scale models. We discuss the general qualities of these models, the underlying framework of the database, and the outlook for the Mosaic’s utility and its future versions.
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.
The U.S. Geological Survey's PAGER alert system provides rapid (1020 min) but general loss estimates of ranges of fatalities and economic impact for significant global earthquakes. FEMA's Hazus software, in contrast, provides time consuming (25 hours) but more detailed loss information quantified in terms of structural, social, and economic consequences estimated at a much higher spatial resolution for large domestic earthquakes. We developed a rapid hybrid post-earthquake product that takes advantage of the best of both loss models. First, though, we conducted a systematic comparison of loss estimates from PAGER with Hazus for all significant, relatively recent, domestic earthquakes for which adequate loss data exist augmented by a dozen ShakeMap scenarios. The systematic comparison of Hazus and PAGER losses provided the basis for selecting the specific loss metrics to present from each system. The signature product will serve as a supplement to the widely deployed PAGER alerts product for significant domestic earthquakes.
The majority of the existing seismic risk studies use a deterministic approach to define vulnerability functions, despite the well-recognized large variability in the probability of loss ratio conditional on ground shaking intensities. This study explored a statistical framework to simulate this variability, considering the existing correlation between assets separated by a given distance. The impact that these vulnerability modeling approaches may have in probabilistic seismic risk assessment is evaluated considering three fictitious building portfolios with distinct characteristics. To this end, loss exceedance curves and average annualized losses are compared, and recommendations are drawn regarding the optimal vulnerability modeling approach.
The evaluation of the potential impact of strong seismic events shortly after their occurrence is a critical step to organise emergency response and consequently minimise the adverse effects of earthquakes. The estimation of the impact from earthquakes considering the observed ground shaking from past events can be useful for the calibration of existing exposure and/or fragility and vulnerability models. This study describes a methodology to combine the publicly available information from the USGS ShakeMap system and the open‐source software OpenQuake engine for the assessment of damage and losses. This approach is employed to estimate the number of structural collapses considering the 2012 Magnitude 5.9 Emilia‐Romagna (Italy) earthquake and the aggregated economic loss because of the 2010 Magnitude 7.1 Darfield (New Zealand) event. Several techniques to calculate the ground shaking in the affected region considering the spatial and interperiod correlations in the intra‐event ground motion residuals are investigated and their influence in the resulting damage or loss estimates are evaluated.
Assessment of human casualties in earthquakes has become a topic of vital importance for national and urban authorities responsible for emergency provision, for the development of mitigation strategies and for the development of adequate insurance schemes. In the last few years important work has been carried out on a number of recent events (including earthquakes in Kocaeli, Turkey 1999, Niigata Japan, 2004, Sichuan, China 2008 and L'Aquila,Italy 2009). These events have created new and detailed casualty data, which has not until now been properly assembled and evaluated. This book draws the new evidence from recent events together with existing knowledge. It summarises current trends in the understanding of the factors influencing the numbers and types of casualties in earthquakes; it offers methods to incorporate this understanding into the estimation of losses in future events in different parts of the world; it discusses ways in which pre-event mitigation activity and post-event emergency management can reduce the toll of casualties in future events; and it identifies future research needs. Audience: This book will be of interest to scientists and professionals in engineering, geography, emergency management, epidemiology and the insurance industry.
Within minutes of a significant earthquake anywhere on the globe, the U.S. Geological Survey (USGS) Prompt Assessment of Global Earthquakes for Response (PAGER) system assesses its potential societal impact. PAGER automatically estimates the number of people exposed to severe ground shaking and the shaking intensity at affected cities. Accompanying maps of the epicentral region show the population distribution and estimated ground-shaking intensity. A regionally specific comment describes the inferred vulnerability of the regional building inventory and, when available, lists recent nearby earthquakes and their effects. PAGER’s results are posted on the USGS Earthquake Program Web site (http://earthquake.usgs.gov/), consolidated in a concise one-page report, and sent in near real-time to emergency responders, government agencies, and the media. Both rapid and accurate results are obtained through manual and automatic updates of PAGER’s content in the hours following significant earthquakes. These updates incorporate the most recent estimates of earthquake location, magnitude, faulting geometry, and first-hand accounts of shaking. PAGER relies on a rich set of earthquake analysis and assessment tools operated by the USGS and contributing Advanced National Seismic System (ANSS) regional networks. A focused research effort is underway to extend PAGER’s near real-time capabilities beyond population exposure to quantitative estimates of fatalities, injuries, and displaced population.
The evaluation of earthquake damage considering past events can be a useful tool to verify or calibrate damage and risk models, as well as to assess the possible consequences that future events may cause in a region. This study describes a process to estimate earthquake damage considering past events, and using the OpenQuake-engine, the open-source software for seismic hazard and risk analysis of the Global Earthquake Model Foundation. Exposure and fragility models from the recently completed South America Risk Assessment (SARA) project were combined with conditioned ground motion fields from past events to calculate structural damage in the affected region. These results can facilitate the creation of risk reduction measures, such as retrofitting campaigns, development of insurance mechanisms and enhancement of building codes. The challenges in assessing damage and losses from past events are thoroughly discussed, and several recommendations are proposed.
Approximately 43% of Canada’s population reside in urban centres at most seismic risk.This research creates practical and proactive tools to support decision making in emergency management regarding earthquake risk. This proactive approach evaluates the potential impact of future earthquakes for informed mitigation and preparedness decisions. The overall aims are to evaluate a community’s operational readiness, reveal limitations and resources gaps in the emergency plan, test potential mitigation and preparedness strategies and provide a realistic earthquake scenario for training activities. Two models, the CanRisk injury model and a disaster Spatial Decision Support System (SDSS), were designed and developed to further evaluate seismic risk on a community scale.
The injury model is an extension of the engineering-based CanRisk tool and quantifies an individual’s risk to injury, the number of injuries, and provides an injury profile of life-threatening injuries at the building scale. The model implements fuzzy synthetic evaluation to quantify seismic risk, mathematical calculations to estimate number of injuries, and a decision-matrix to generate the injury profile.
The SDSS is an evidence-based model that is designed for the planning phase to evaluate post-earthquake emergency response. Loss estimations from Hazus Canada and the CanRisk injury model are combined with community geospatial data to simulate post-earthquake conditions that are important for immediate post-earthquake response. Fire services, search and rescue operations (including urban search and rescue and police services), emergency medical services, and relief operations are all modelled.
A case study was applied to 27 neighbourhoods in Ottawa, Canada, using a M6.0 and M7.25 scenarios. The models revealed challenges to all emergency response units. A critical threshold exists between the M6.0 and M7.25 scenarios whereby emergency response moves from partial but manageable functionality to a complete system breakdown. The models developed in this research show great utility to emergency managers in Canada.
http://hdl.handle.net/10393/31536
This paper describes building damage functions that were developed for the FEMA/NIBS earthquake loss estimation methodology (Whitman et al., 1997). These functions estimate the probability of discrete states of structural and nonstructural building damage that are used as inputs to the estimation of building losses, including economic loss, casualties and loss of function (Kircher et al., 1997). These functions are of a new form and represent a significant step forward in the prediction of earthquake impacts. Unlike previous building damage models that are based on Modified Mercalli Intensity, the new functions use quantitative measures of ground shaking (and ground failure) and analyze model building types in a similar manner to the engineering analysis of a single structure.
Modern global earthquake fatalities can be separated into two components: (1) fatalities from an approximately constant annual background rate that is independent of world population growth and (2) fatalities caused by earthquakes with large human death tolls, the frequency of which is dependent on world population. Earthquakes with death tolls greater than 100,000 (and 50,000) have increased with world population and obey a nonstationary Poisson distribution with rate proportional to population. We predict that the number of earthquakes with death tolls greater than 100,000 (50,000) will increase in the 21st century to 8.7±3.3 (20.5±4.3) from 4 (7) observed in the 20th century if world population reaches 10.1 billion in 2100. Combining fatalities caused by the background rate with fatalities caused by catastrophic earthquakes (>100,000 fatalities) indicates global fatalities in the 21st century will be 2.57±0.64 million if the average post- 1900 death toll for catastrophic earthquakes (193,000) is assumed.
This study examines the expected cost of repairing earthquake damage in a set of 30 archetype reinforced concrete moment frame buildings. Varying in height from 1 to 20 stories, these archetype buildings are representative of office buildings with special RC moment frames, designed according to modern seismic codes. Economic losses associated with repair are computed using a performance‐based earthquake engineering framework, which integrates the site‐specific seismic hazard, structural response, damage to building components and contents, and the resulting repair costs. Results are presented in terms of expected losses under the design basis earthquake, expected annual losses, and present value of life cycle losses. Expected annual economic losses for the set of RC frame buildings are approximately 1.0% of building replacement cost for the high seismic California site considered. Repair costs are shown to vary significantly depending on building height and other architectural and structural design parameters. These metrics provide important information about the level of economic losses expected in code‐conforming structures and the effect of design decisions on the earthquake losses. Copyright © 2012 John Wiley & Sons, Ltd.
Recent earthquakes such as the Haiti earthquake of 12 January 2010 and the Qinghai earthquake on 14 April 2010 have highlighted the importance of rapid estimation of casualties after the event for humanitarian response. Both of these events resulted in surprisingly high death tolls, casualties and survivors made homeless. In the Mw = 7.0 Haiti earthquake, over 200,000 people perished with more than 300,000 reported injuries and 2 million made homeless. The Mw = 6.9 earthquake in Qinghai resulted in over 2,000 deaths with a further 11,000 people with serious or moderate injuries and 100,000 people have been left homeless in this mountainous region of China. In such events relief efforts can be significantly benefitted by the availability of rapid estimation and mapping of expected casualties. This paper contributes to ongoing global efforts to estimate probable earthquake casualties very rapidly after an earthquake has taken place. The analysis uses the assembled empirical damage and casualty data in the Cambridge Earthquake Impacts Database (CEQID) and explores data by event and across events to test the relationships of building and fatality distributions to the main explanatory variables of building type, building damage level and earthquake intensity. The prototype global casualty estimation model described here uses a semi-empirical approach that estimates damage rates for different classes of buildings present in the local building stock, and then relates fatality rates to the damage rates of each class of buildings. This approach accounts for the effect of the very different types of buildings (by climatic zone, urban or rural location, culture, income level etc), on casualties. The resulting casualty parameters were tested against the overall casualty data from several historical earthquakes in CEQID; a reasonable fit was found.
We analyzed mortality rates of earthquakes worldwide and developed a country/region-specific empirical model for earthquake fatality estimation within the U.S. Geological Survey's Prompt Assessment of Global Earthquakes for Response (PAGER) system. The earthquake fatality rate is defined as total killed divided by total population exposed at specific shaking intensity level. The total fatalities for a given earthquake are estimated by multiplying the number of people exposed at each shaking intensity level by the fatality rates for that level and then summing them at all relevant shaking intensities. The fatality rate is expressed in terms of a two-parameter lognormal cumulative distribution function of shaking intensity. The parameters are obtained for each country or a region by minimizing the residual error in hindcasting the total shaking-related deaths from earthquakes recorded between 1973 and 2007.A new global regionalization scheme is used to combine the fatality data across different countries with similar vulnerability traits.
The human losses after strong earthquakes that occurred in the world during the twentieth century have been analyzed, and
a quantitative model for a preliminary assessment of casualties is proposed. It consists of a correlation between the number
of casualties and the earthquake magnitude as a function of population density. We tackle the distribution of the total number
of casualties within areas of different macroseismic intensity. Prognostic estimations of the expected number of killed or
injured people caused by a supposed strong earthquake in Andalucia (Spain), using the model based on worldwide data, are suggested.
Prognostic estimations based on specific data about the Kanto–Tokai (Japan) region are likewise given and compared with the
number of casualties due to the 1995 Kobe (Japan) earthquake. In relation to the expected number of victims in areas affected
by strong seismic impacts, we compute the casualty rate as the number of people killed divided into the inhabitants of a region
and show its variation for different population density groups in the case of two extreme earthquake magnitudes.