Fast assessment of earthquake loss and its application to the 2008 M_S8.0 Wenchuan earthquake

The paper introduces firstly the seismic loss assessment method based on macro-economic indicators and new vulnerability models determined by the data from the on-site damage and loss survey to earthquakes occurred in China during the last two decades.The fast assessment for the 2008 Wenchuan earthquake with MS8.0 is given based on an empirical intensity attenuation relationship.Compared with the assessment based on the practical seismic intensity map of the event according to the on-site investigation, the...     

四川汶川8级大地震灾害损失快速评估研究/

地震发生之后,在没有开展地震现场调查之前,迅速对地震造成的人员伤亡、直接经济损失等进行评估,对地震应急救援决策非常重要．本文叙述了基于宏观经济指标的地震灾害损失评估方法,根据我国1989——2004年地震现场灾害损失调查资料重新确定的地震易损性模型,给出了汶川8级大地震发生后依据估计的经验地震烈度图得到的地震损失快速评估结果,并与依据现场调查确定的地震烈度分布图给出的地震损失评估结果进行了比较．表明根据近20年我国实际地震震例确定的地震易损性模型具有较好的适用性,损失评估结果的最大不确定来自于对地震影响场的估计．      

Development of damage probability matrices based on Greek earthquake damage data

A comprehensive study is presented for empirical seismic vulnerability assessment of typical structural types, representative of the building stock of Southern Europe, based on a large set of damage statistics. The observational database was obtained from post-earthquake surveys carried out in the area struck by the September 7, 1999 Athens earthquake. After analysis of the collected observational data, a unified damage database has been created which comprises 180,945 damaged buildings from/after the near-field area of the earthquake. The damaged buildings are classified in specific structural types, according to the materials, seismic codes and construction techniques in Southern Europe. The seismic demand is described in terms of both the regional macroseismic intensity and the ratio αg/ao, where αg is the maximum peak ground acceleration (PGA) of the earthquake event and ao is the unique value PGA that characterizes each municipality shown on the Greek hazard map. The relative and cumulative frequencies of the different damage states for each structural type and each intensity level are computed in terms of damage ratio. Damage probability matrices (DPMs) and vulnerability curves are obtained for specific structural types. A comparison analysis is fulfilled between the produced and the existing vulnerability models.     

Rapid estimation of earthquake loss based on instrumental seismic intensity: design and realization

As a result of our ability to acquire large volumes of real-time earthquake observation data, coupled with increased computer performance, near real-time seismic instrument intensity can be obtained by using ground motion data observed by instruments and by using the appropriate spatial interpolation methods. By combining vulnerability study results from earthquake disaster research with earthquake disaster assessment models, we can estimate the losses caused by devastating earthquakes, in an attempt to provide more reliable information for earthquake emergency response and decision support. This paper analyzes the latest progress on the methods of rapid earthquake loss estimation at home and abroad. A new method involving seismic instrument intensity rapid reporting to estimate earthquake loss is proposed and the relevant software is developed. Finally, a case study using the M _L4.9 earthquake that occurred in Shun-chang county, Fujian Province on March 13, 2007 is given as an example of the proposed method.     

On the treatment of uncertainty in seismic vulnerability and portfolio risk assessment

In a related study developed by the authors, building fragility is represented by intensity‐specific distributions of damage exceedance probability of various damage states. The contribution of the latter has been demonstrated in the context of loss estimation of building portfolios, where it is shown that the proposed concept of conditional fragility functions provides the link between seismic intensity and the uncertainty in damage exceedance probabilities. In the present study, this methodology is extended to the definition of building vulnerability, whereby vulnerability functions are characterized by hazard‐consistent distributions of damage ratio per level of primary seismic intensity parameter—Sa(T₁). The latter is further included in a loss assessment framework, in which the impact of variability and spatial correlation of damage ratio in the probabilistic evaluation of seismic loss is accounted for, using test‐bed portfolios of 2, 5, and 8‐story precode reinforced concrete buildings located in the district of Lisbon, Portugal. This methodology is evaluated in comparison with current state‐of‐the‐art methods of vulnerability and loss calculation, highlighting the discrepancies that can arise in loss estimates when the variability and spatial distributions of damage ratio, influenced by ground motion properties other than the considered primary intensity measure, are not taken into account.     

Performance-based methodology for assessing seismic vulnerability and capacity of buildings

This paper presents a performance-based methodology for the assessment of seismic vulnerability and capacity of buildings. The vulnerability assessment methodology is based on the HAZUS methodology and the improved capacity- demand-diagram method. The spectral displacement (Sd) of performance points on a capacity curve is used to estimate the damage level of a building. The relationship between Sd and peak ground acceleration (PGA) is established, and then a new vulnerability function is expressed in terms of PGA. Furthermore, the expected value of the seismic capacity index (SCev) is provided to estimate the seismic capacity of buildings based on the probability distribution of damage levels and the corresponding seismic capacity index. The results indicate that the proposed vulnerability methodology is able to assess seismic damage of a large number of building stock directly and quickly following an earthquake. The SCev provides an effective index to measure the seismic capacity of buildings and illustrate the relationship between the seismic capacity of buildings and seismic action. The estimated result is compared with damage surveys of the cities of Dujiangyan and Jiangyou in the M8.0 Wenchuan earthquake, revealing that the methodology is acceptable for seismic risk assessment and decision making. The primary reasons for discrepancies between the estimated results and the damage surveys are discussed.     

青海玛多7.4级地震烈度快速评估

利用青海地震烈度衰减模型和基于断层最短距离的地震动参数衰减模型对青海玛多7.4级地震的烈度分布进行快速评估,将评估结果与实际烈度图对比分析。研究结果表明:两种模型可以在地震正式速报后1分钟内得到地震烈度分布的快速评估结果,时效性强,可以在最短的时间内为应急指挥和救援工作提供参考;青海地震烈度衰减模型计算结果比较理想化,在大致范围上有一定的参考性,但在重灾区范围上与此次实际结果存在偏差;基于断层最短距离的地震动参数衰减模型的PGV-v_(S30)计算结果较青海地震烈度衰减模型更为精细,在高烈度区的评估中具有较好的实际应用价值;相较于冉洪流等研究的地表破裂与震级的经验关系,Wells等研究的经验关系在本次地震中的适用性更好。文章研究结果在此次实际地震应急响应中进行了应用,为政府应急指挥决策和应急救援提供了重要数据支撑。     

川南地区砖混结构房屋典型震害及地震易损性研究

以川南地区为研究区,并以在建造方式上具有明显当地地域特征的砖混结构房屋为研究对象,结合砖混结构房屋建造特点及川南历史地震(如长宁6.0级地震)震害调查结果等,分析砖混结构房屋典型震害特征,统计其在不同烈度下不同破坏等级的比例,采用经验分析法得到初步的易损性矩阵。在此基础上,针对因样本局限性造成的结构在高烈度下破坏比例不全,使实际易损性矩阵缺失的问题,通过插值法,推算高烈度下的破坏比例,补全经验易损性矩阵,拟合出易损性曲线,建立以震害统计为主、数值模拟为辅的砖混结构易损性分析模型;并基于平均震害指数对比分析,对易损性分析的可靠性进行检验。结果表明,构建的易损性矩阵能客观反映川南地区砖混结构房屋的抗震能力,对开展震害预测、灾害损失评估及震害风险评估等工作具有实际应用价值。     

On the use of JMA intensity in earthquake early warning systems

The estimation of strength of shaking at a site from the initial P-wave portion of ground motion is the key problems for shortening the alert time of the earthquake Early Warning (EEW). The most of the techniques proposed for the purpose utilize (a) ground motion models based on the estimated magnitude and hypocentral distance, or (b) the interim proxies, such as initial vertical displacement P _d . We suggest the instrumental Japan Meteorological Agency (JMA) intensity (JMA_I) as a characteristic for fast estimation of damage potential in the EEW systems. We investigated the scaling relations between JMA_I measured using the whole earthquake recordings (overall intensity) and using particular time intervals of various duration (2.0–8.0 s) starting from the P-wave arrival (preliminary intensity). The dataset included 3,660 records (K-NET and the KiK-net networks) from 55 events (M _W 4.1–7.4) occurred in 1999–2008 in Japan. We showed that the time interval of 4–5 s from the P-wave arrival can be used for reliable estimations of the overall intensity with the average standard error of about 0.5 JMA units. The uncertainty in the prediction may be reduced by consideration of local site conditions or by development of the station-specific models.     

A hybrid method for the vulnerability assessment of R/C and URM buildings

The methodology followed by the Aristotle University (AUTh) team for the vulnerability assessment of reinforced concrete (R/C) and unreinforced masonry (URM) structures is presented. The paper focuses on the derivation of vulnerability (fragility) curves in terms of peak ground acceleration (PGA), as well as spectral displacement (s _d), and also includes the estimation of capacity curves, for several R/C and URM building types. The vulnerability assessment methodology is based on the hybrid approach developed at AUTh, which combines statistical data with appropriately processed (utilising repair cost models) results from nonlinear dynamic or static analyses, that permit extrapolation of statistical data to PGA’s and/or spectral displacements for which no data are available. The statistical data used herein are from earthquake-damaged greek buildings. An extensive numerical study is carried out, wherein a large number of building types (representing most of the common typologies in S. Europe) are modelled and analysed. Vulnerability curves for several damage states are then derived using the aforementioned hybrid approach. These curves are subsequently used in combination with the mean spectrum of the Microzonation study of Thessaloniki as the basis for the derivation of new vulnerability curves involving spectral quantities. Pushover curves are derived for all building types, then reduced to standard capacity curves, and can easily be used together with the S _d fragility curves as an alternative for developing seismic risk scenarios.     

2017年5月11日新疆塔什库尔干5.5级地震生命损失评估对比分析

2017年5月11日,新疆喀什地区塔什库尔干县发生5.5级地震。地震造成8人死亡、31人受伤以及财产损失,属于典型的“小震大灾”。按照一般的地震灾害损失快速评估方法,得到的评估结果与实际结果差别较大。为探讨评估结果偏离的原因,本文对不同地震损失评估方案进行比较分析,探讨了地震致灾性（地震影响场分布）、承灾体（人口）分布等因素对地震损失评估结果的影响。结果表明在此次地震快速评估中,基于宏观震中确定的地震影响场较微观震中更接近实际分布;地震烈度衰减的平均估计模型给出的地震烈度区面积明显小于实际面积;极震区存在抗震能力相对低的土木、砖木结构房屋,是造成该地震震级相对小而生命损失相对大的“小震大灾”的重要原因。对比分析结果表明,提高人口、房屋建筑等风险暴露数据的空间精准性,改善地震震中定位与地震影响场估计的准确性,将有助于提高地震应急损失评估的准确性。     

Vulnerability of floating tunnel shafts for increasing earthquake loading

Fragility curves constitute the cornerstone in seismic risk evaluations and performance-based earthquake engineering. They describe the probability of a structure to experience a certain damage level for a given earthquake intensity measure, providing a relationship between seismic hazard and vulnerability. In this paper a numerical approach is applied to derive fragility curves for tunnel shafts built in clays, a component that is found in several critical infrastructure such as urban metro networks, airport facilities or water and waste water projects. The seismic response of a representative tunnel shaft is assessed using tridimensional finite difference non-linear analyses carried out with the program FLAC^3D, under increasing levels of seismic intensity. A hysteretic model is used to simulate the soil non-linear behavior during the seismic event. The effect of soil conditions and ground motion characteristics on the soil-structure system response is accounted for in the analyses. The damage is defined based on the exceedance of the concrete wall shaft capacity due to the developed seismic forces. The fragility curves are estimated in terms of peak ground acceleration at a rock or stiff soil outcrop, based on the evolution of damage with increasing earthquake intensity. The proposed fragility models allows the characterization of the seismic risk of a representative tunnel shaft typology and soil conditions considering the associated uncertainties, and partially fill the gap of data required in performing a risk analysis assessment of tunnels shafts.     

Prediction of spatially distributed seismic demands in specific structures: Structural response to loss estimation

A companion paper has investigated the effects of intensity measure (IM) selection in the prediction of spatially distributed response in a multi‐degree‐of‐freedom structure. This paper extends from structural response prediction to performance assessment metrics such as probability of structural collapse; probability of exceeding a specified level of demand or direct repair cost; and the distribution of direct repair loss for a given level of ground motion. In addition, a method is proposed to account for the effect of varying seismological properties of ground motions on seismic demand that does not require different ground motion records to be used for each intensity level. Results illustrate that the conventional IM, spectral displacement at the first mode, S_de(T₁), produces higher risk estimates than alternative velocity‐based IM's, namely spectrum intensity, SI, and peak ground velocity, PGV, because of its high uncertainty in ground motion prediction and poor efficiency in predicting peak acceleration demands. Copyright © 2009 John Wiley & Sons, Ltd.     

Seismic vulnerability assessment to slight damage based on experimental modal parameters

The aim of this paper is to adjust behaviour models for each class of structure for vulnerability assessment by using ambient vibration. A simple model based on frequencies, mode shapes and damping, taken from ambient vibrations, allows computation of the response of the structures and comparison of inter‐storey drifts with the limits found in the literature for the slight damage grade, considered here as the limit of elastic behaviour. Two complete methodologies for building fragility curves are proposed: (1) using a multi‐degree of freedom system including higher modes and full seismic ground‐motion and (2) using a single‐degree of freedom model considering the fundamental mode f₀ of the structure and ground‐motion displacement response spectra S_D(f₀). These two methods were applied to the city of Grenoble, where 60 buildings were studied. Fragility curves for slight damage were derived for the various masonry and reinforced concrete classes of buildings. A site‐specific earthquake scenario, taking into account local site conditions, was considered, corresponding to an M_L = 5.5 earthquake at a distance of 15 km. The results show the benefits of using experimental models to reduce variability of the slight damage fragility curve. Moreover, by introducing the experimental modal model of the buildings, it is possible to improve seismic risk assessment at an overall scale (the city) or a local scale (the building) for the first damage grade (slight damage). This level of damage, of great interest for moderate seismic‐prone regions, may contribute to the seismic loss assessment. Copyright © 2011 John Wiley & Sons, Ltd.     

On the treatment of uncertainties in the development of fragility functions for earthquake loss estimation of building portfolios

State‐of‐the‐art methods for the assessment of building fragility consider the structural capacity and seismic demand variability in the estimation of the probability of exceeding different damage states. However, questions remain regarding the appropriate treatment of such sources of uncertainty from a statistical significance perspective. In this study, material, geometrical and mechanical properties of a number of building classes are simulated by means of a Monte Carlo sampling process in which the statistical distribution of the aforementioned parameters is taken into consideration. Record selection is performed in accordance with hazard‐consistent distributions of a comprehensive set of intensity measures, and issues related with sufficiency, efficiency, predictability and scaling robustness are addressed. Based on the appraised minimum number of ground motion records required to achieve statistically meaningful estimates of response variability conditioned on different levels of seismic intensity, the concept of conditional fragility functions is presented. These functions translate the probability of exceeding a set of damage states as a function of a secondary sufficient intensity measure, when records are selected and scaled for a particular level of primary seismic intensity parameter. It is demonstrated that this process allows a hazard‐consistent and statistically meaningful representation of uncertainty and correlation in the estimation of intensity‐dependent damage exceedance probabilities. Copyright © 2016 John Wiley & Sons, Ltd.     

Seismic vulnerability assessment based on typological characteristics. The first level procedure “SAVE”

In this paper a procedure is described for quick seismic vulnerability assessment according to the EMS 98 classification. The criteria adopted by Ems 98 to assign the typological classes are mainly based on the vertical structure type. The proposed methodology aims to reduce the uncertainty in the class assessment using a set of parameters, related to typological features, that are identified as modifiers of the vulnerability level. The paper shows how the weight of each of these parameters is evaluated through the analysis of the seismic damages recorded during past earthquakes. A synthetic damage parameter is then defined in order to compare the seismic response of different sets of buildings under the same seismic intensity. Finally, the vulnerability assessment obtained on a set of buildings by the application of the methodology is compared with expert evaluations derived from the direct inspections on buildings.     

Loss estimation for non‐ductile reinforced concrete building in Victoria,British Columbia,Canada: effects of mega‐thrust Mw9‐class subduction earthquakes and aftershocks

This paper presents, within the performance‐based earthquake engineering framework, a comprehensive probabilistic seismic loss estimation method that accounts for main sources of uncertainty related to hazard, vulnerability, and loss. The loss assessment rigorously integrates multiple engineering demand parameters (maximum and residual inter‐story drift ratio and peak floor acceleration) with consideration of mainshock–aftershock sequences. A 4‐story non‐ductile reinforced concrete building located in Victoria, British Colombia, Canada, is considered as a case study. For 100 mainshock and mainshock–aftershock earthquake records, incremental dynamic analysis is performed, and the three engineering demand parameters are fitted with a probability distribution and corresponding dependence computed. Finally, with consideration of different demolition limit states, loss assessment is performed. From the results, it can be shown that when seismic vulnerability models are integrated with seismic hazard, the aftershock effects are relatively minor in terms of overall seismic loss (1–4% increase). Moreover, demolition limit state parameters, uncertainties of collapse fragility, and non‐collapse seismic demand prediction models have showed significant contribution to the loss assessment. The seismic loss curves for the reference case and for cases with the varied parameters can differ by as large as about 150%. Copyright © 2015 John Wiley & Sons, Ltd.     

2013年四川芦山7.0级地震烈度遥感评估

2013年4月20日四川芦山MS7.0级地震发生后,在灾区应急获取了多种高分辨率航空和无人机遥感影像,并快速解译提取了灾区建筑物震害信息.采用地震烈度遥感定量评估方法,利用2008年汶川8.0级地震等震后震害遥感解译和现场调查研究确定的经验震害遥感定量评估模型,获得了芦山地震灾区126个主要居民点的地震烈度遥感评估结果,并据此圈画了地震烈度分布遥感评估图.结果显示,本次地震Ⅸ度区面积约150km2,Ⅷ度区面积约900km2.该结果在第一时间(4月21日晚)提供给了中国地震局地震现场应急指挥部.对比分析显示,地震烈度遥感快速评估结果与中国地震局4月25日公布的地震烈度图,以及与笔者在现场实地进行的建筑物震害详细调查结果基础上评定的地震烈度具有较高的一致性.表明强烈地震发生后,借助于快速获取的灾区高分辨率遥感影像,可以快速估计地震烈度分布,对地震灾区灾情估计和抗震救灾工作具有十分重要的参考意义.     

Weighing the importance of model uncertainty against parameter uncertainty in earthquake loss assessments

Epistemic uncertainties can be classified into two major categories: parameter and model. While the first one stems from the difficulties in estimating the values of input model parameters, the second comes from the difficulties in selecting the appropriate type of model. Investigating their combined effects and ranking each of them in terms of their influence on the predicted losses can be useful in guiding future investigations. In this context, we propose a strategy relying on variance-based global sensitivity analysis, which is demonstrated using an earthquake loss assessment for Pointe-à-Pitre (Guadeloupe, France). For the considered assumptions, we show: that uncertainty of losses would be greatly reduced if all the models could be unambiguously selected; and that the most influential source of uncertainty (whether of parameter or model type) corresponds to the seismic activity group. Finally, a sampling strategy was proposed to test the influence of the experts’ weights on models and on the assumed coefficients of variation of parameter uncertainty. The former influenced the sensitivity measures of the model uncertainties, whereas the latter could completely change the importance rank of the uncertainties associated to the vulnerability assessment step.     

地震速报参数不确定性的应急灾害损失快速评估模型

本文针对目前地震应急灾害损失快速评估中存在的问题,建立了考虑地震速报参数不确定性的灾害损失快速评估模型。并利用1990年来全国的81组速报震中与宏观震中数据。得到速报震中与宏观震中偏差的概率分布经验参数。