Ground‐motion intensity and damage map selection for probabilistic infrastructure network risk assessment using optimization

In many parts of the world, earthquakes threaten regional infrastructure systems. For modeling risk using stochastic earthquake catalogs, random variables include rupture location and the damage state of different components. Thus, there is an infinite set of possible damage maps that a risk modeler could evaluate in an event‐based probabilistic loss model. Even a finite but large number of damage maps may not be practical, because many network performance measures are computationally expensive. Here, we show a computationally efficient method for selecting a subset of damage maps, corresponding ground‐motion intensity maps, and associated occurrence rates that reasonably estimates the full distribution of the ground‐motion intensity and a target performance measure using optimization. The method chooses a subset of maps and associated annual rates of occurrence that minimizes the error in estimating the distribution of a network performance measure as well as the marginal distributions of ground‐motion intensity exceedance. The joint distribution of the ground‐motion intensity is implicitly included in the objective function of the optimization problem via the network performance measure. We then show how to tune the optimization parameters based on consistency checks related to the network performance measure and the ground‐motion hazard. We illustrate the proposed method with a case study of the San Francisco Bay Area road network to estimate the exceedance curve of the average percentage change in morning commute trip time. This work facilitates expanded and risk‐consistent studies of the impacts of infrastructure networks on regional seismic risk and resiliency. Copyright © 2014 John Wiley & Sons, Ltd.     

经验震害矩阵的完善方法研究

近年来我国发生的几次大地震有一些是发生在低烈度区,对地震区已有的建筑物应当怎样来评价它的抗震能力,本文对此进行了探索性的研究。通过将破坏概率离散化得出一次地震中各烈度下震害指数的均值和方差,对比其与标准震害矩阵相应烈度下的值,得到其他烈度下震害指数的均值和方差。我们假设各烈度下震害指数分布都服从Beta分布,由均值和方差反算出Beta分布的未知参数,从而得出其他烈度下各破坏等级的概率值。用本文方法得到的震害矩阵,可为该地区的震害预测和经济损失评估提供科学依据。计算结果表明,本文的方法是可行的。     

地震灾害快速自动评级方法研究

发生地震时,需根据本次灾害的各个方面的损失程度来确定最终的应急响应级别,目前的地震等级评估办法,主要参考受伤死亡人数、房屋损伤程度、经济损失情况、烈度等,其中部分参考因素需震后较长时间调查之后才能获取,无法及时为应急响应提供参考.利用回归分析方法,对我国历史上大量地震数据进行分析,提出一种地震灾害快速自动评级的方法,综...     

Aftershock risk assessment and the decision to open traffic on bridges

Critical issues in emergency management after a seismic event are assessing the functionality of the main infrastructures (hospitals, road network, etc.) and deciding on their usability just after the mainshock. The use of a pure analytical tool to assess the aftershock risk of a structure can be contrasted with the limited time available to make a decision about the usability of a structure. For this reason, this paper presents a method for evaluating post‐earthquake bridge practicability based on a rational combination of information derived from numerical analyses and in situ inspections. In particular, we propose an effective tool to speed up the decision‐making process involved in evaluating the seismic risk of mainshock‐damaged bridges in the context of aftershocks. The risk is calculated by combining the aftershock hazard using the Omori law and the fragility curves of the structure, which are calculated using the regression analysis of a sample of results obtained with data randomly generated by the Latin Hypercube Sampling technique and updated based on the results of in situ inspection. Different decision criteria regarding the practicability of bridges are discussed, and a new criterion is proposed. This tool was applied to an old highway RC viaduct. There are two main findings, including the high sensitivity to Bayesian updating (especially when the damage predicted by numerical analysis does not match the real damage) and the criteria used to decide when re‐open bridges to traffic. Copyright © 2013 John Wiley & Sons, Ltd.     

铁路梁式桥地震灾害损失评估

针对铁路桥梁地震灾害评估中多因素影响问题,结合铁路桥梁地震灾害的复杂特点和各结构层次的震害表现形式,从桥面系、上部结构和下部结构3个方面构建铁路梁式桥地震灾害评估指标体系.基于改进的层次分析法计算了各评估指标的权重,以桥梁承灾系统为研究主体,运用多级综合模糊理论,建立铁路梁式桥震害评估模型.结合汶川地震中一座铁路混凝土...     

伽师强震群活动期间地震窗异常特征研究

分析研究了1997－1998年伽师强震群活动期间阿困什余震窗和喀什地震窗月频、旬频、日频的异常特征。结果表明,两地震窗的异常形态具有一定的相似性,起止时间也具有同步性。月频度异常形态多经过2－3个峰值后在高值发震;旬频率、日频率异常形态则表现为高值－低值－发震;日频度异常出现在震前1－3d。通过对比分析伽师强震群1997年和1998年的活动特征发现,阿图什余震窗和喀什余震窗在1997年几组后续6级地震前小震日频率均在指数衰减背景上明显升高,而1998年2组强震前指数衰减背景不明显。     

海南区域地震与爆破震源参数特征

收集2008年以来海南测震台网记录的M_L 2.5以上地震及爆破资料,利用Brune圆盘模型,计算得出震源参数,发现地震、爆破的震源参数特征为:地震的拐角频率绝大多数大于爆破;地震应力降大于1,爆破应力降小于1;地震震源尺度绝大多数小于爆破。对一个有感疑爆事件,利用其拐角频率、应力降、震源尺度等参数,判定该事件为天然地震,与前人研究结果一致。由此可见,利用震源参数在地震速报、日常分析中判定事件类型具有实际意义。     

Earthquake physical damage and functional serviceability of lifeline network models

The connectivity of lifeline systems is studied in this paper in terms of two ratios: ‘damage ratio’, which is the degree of physical damage to the system, and is defined as the expected number of failures per unit length or per link; and ‘service ratio’, which is a measurement of system operation. First, the relationship between the two ratios in a historic event is examined. Second, a method is developed for determining this relationship in simple network systems immediately following an earthquake. Density function, expected value and covariance of service ratio are calculated as functions of the damage ratio. Even in a simple checkerboard-type network, the density function of the service ratio has two peaks. Third, the variation in reliability of the network is examined with respect to difference in scale and configuration of the network, which may accompany growth of the community. When the damage ratio is small, the service ratio of a complex network is as large as, or larger, than that of a simple network. This pattern is, however, reversed for larger damage ratios. Finally, the relationship prior to operation restoration is examined. During the initial stages of restoration, the service ratio increases steeply, almost linearly, with decrease in the damage ratio. The increase then slows in the last stages of restoration.     

Reconnaissance report and preliminary ground motion simulation of the 12 May 2008 Wenchuan earthquake

The M _w = 8.0 Wenchuan earthquake of May 12, 2008, caused destruction over a wide area. The earthquake cost more than 69,000 lives and the damage is reported to have left more than 5 million people homeless. It is estimated that 5.36 million buildings were destroyed and 21 million buildings were damaged in Sichuan and the nearby provinces. Economic losses due to the event are estimated to be 124 billion USD. From a field reconnaissance trip conducted in October 2008, it is evident that the combination of several factors, including mountainous landscape, strong ground shaking, extensive landslides and rock-falls, has exacerbated the human and economic consequences of this earthquake. Extensive damage occurred over a wide area due to the shear size of the earthquake rupture combined with poor quality building construction. In order to investigate the ground shaking during the earthquake, we have conducted a strong ground motion simulation study, applying a hybrid broadband frequency technique. The preliminary results show large spatial variation in the ground shaking, with the strongest ground motions along the fault plane. The simulation results have been calibrated against the recorded ground motion from several near-field stations in the area, and acceleration values of the order of 1 g are obtained, similar to what was recorded during the event. Comparison with the damage distribution observed in the field confirms that the effect of fault rupture complexity on the resulting ground motion distribution also controls to a large extent the damage distribution. The applied simulation technique provides a promising platform for predictive studies.     

基于改进的风险矩阵法的生命线网络地震脆弱性分析

生命线网络的脆弱性不单单只表示地震发生后对网络作用而产生的后果,还应该包括网络的连通情况。本文在重新确定生命线网络脆弱性定义的基础上,运用风险评估理论中的风险矩阵方法综合考虑生命线网络的连通性能和失效后果两个方面来评价生命线网络的脆弱性,并以一个供气管网为例说明改进的风险矩阵法评价生命线网络脆弱性的有效性和合理性,找出供气管网中脆弱性等级最高的节点,分析其脆弱性等级最高的原因,以便于重点保护,并降低网络的脆弱性。     

汶川地震道路破坏机理浅析

基于2008年汶川地震道路破坏数据与破坏现象,对道路构件（挡土墙、边坡和路基路面）震害相关因素进行统计,宏观分析统计结果。根据道路构件不同的破坏形式进行分类,总结每类破坏形式常见的自然地质条件及工程因素,并给出地震作用下道路构件震害发生机理,加深对公路系统震损特征的了解,有利于因地制宜地提高道路抗震能力和震后恢复能力。     

初探地震活动的时间分维特征

本文运用分维的概念和方法,对我国部分强震前地震活动时间分维,前震震群活动时间分维,7级以上大地震的余震活动时间分维和小震群活动时间分维进行了计算。初步结果表明,同一类型的地震活动(如强震前较大时空范围内地震活动、强震的余震、前震震群、小震群等类型)的时间分维十分相近,而不同类型地震活动的时间分维存在着差异,一般说来,强震前的地震活动比较普遍地存在降维现象,表现出临近强震时,震源及附近地区地震活动时间结构的有序性增强。这为地震预报开辟了一个新的途径。     

Combining USGS ShakeMaps and the OpenQuake-engine for damage and loss assessment

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.     

A determination of source properties of large intraplate earthquakes in Alaska

Historically, large and potentially hazardous earthquakes have occurred within the interior of Alaska. However, most have not been adequately studied using modern methods of waveform modeling. The 22 July 1937, 16 October 1947, and 7 April 1958 earthquakes are three of the largest events known to have occurred within central Alaska (M _s =7.3,M _s =7.2 andM _s =7.3, respectively). We analyzed teleseismic body waves to gain information about the focal parameters of these events. In order to deconvolve the source time functions from teleseismic records, we first attempted to improve upon the published focal mechanisms for each event. Synthetic seismograms were computed for different source parameters, using the reflectivity method. A search was completed which compared the hand-digitized data with a suite of synthetic traces covering the complete parameter space of strike, dip, and slip direction. In this way, the focal mechanism showing the maximum correlation between the observed and calculated traces was found. Source time functions, i.e., the moment release as a function of time, were then deconvolved from teleseismic records for the three historical earthquakes, using the focal mechanisms which best fit the data. From these deconvolutions, we also recovered the depth of the events and their seismic moments. The earthquakes were all found to have a shallow foci, with depths of less than 10 km.The 1937 earthquake occurred within a northeast-southwest band of seismicity termed the Salcha seismic zone (SSZ). We confirm the previously published focal mechanism, indicating strike-slip faulting, with one focal plane parallel to the SSZ which was interpreted as the fault plane. Assuming a unilateral fault model and a reasonable rupture velocity of between 2 and 3 km/s, the 21 second rupture duration for this event indicates that all of the 65 km long SSZ may have ruptured during this event. The 1947 event, located to the south of the northwest-southeast trending Fairbanks seismic zone, was found to have a duration of about 11 seconds, thus indicating a rupture length of up to 30 km. The rupture duration of the 1958 earthquake, which occurred near the town of Huslia, approximately 400 km ENE of Fairbanks, was found to be about 9 seconds. This gives a rupture length consistent with the observed damage, an area of 16 km by 64 km.     

道路网络抗震功能失效空间决策支持方法研究

地震作用后桥梁的破坏是导致道路网络功能失效的主要原因。在进行道路网络抗震功能失效分析这一决策过程中,不仅要应用空间分析模型对空间数据进行分析,而且也要对属性数据进行有效的决策分析,因此本文结合了G IS(地理信息系统)与DSS(决策支持系统),形成了以模型库为驱动核心的道路网络抗震功能失效分析空间决策支持,本文着重对数据库及模型库的构建进行了深入研究。     

Earthquake arrival identification in a record with technogenic noise

Analysis of the problem of seismic event identification at an increased level of noise, by the data of a single sensor or local group of sensors, is made. This problem is the key to development of an ultra-short-term warning system of an earthquake that has occurred. Catastrophic damage and human deaths are usually caused by the sudden character of earthquake occurrence. If data processing could be done rapidly (i.e., within 4–5 s), such an earthquake warning would be of value for decreasing human deaths and economic damage. The aim of the present study is to investigate the selection of information features of signals in order to reduce the feature dimensionality and to incorporate the particular features of self-contained systems. Special emphasis is placed on the possibility of neural network techniques for the analysis of class separability in the attribute space. Our system will be helpful for reducing the impact of a disastrous earthquake. The main problems are highlighted and the methods for their solution are discussed; tests are carried out for a test problem, consisting in detection of small earthquakes in a noise-contaminated record. It is intended to develop algorithms and programs for identification of earthquake phase arrivals at an increased level of industrial and other noise. Further work will consist in designing instrumental solutions of the system.     

汶川地震交通系统震害及震后抢修

2008年5月12日下午2点28分在我国四川省汶川发生的8．0级强烈地震,是我国1976年唐山7．8级地震以来破坏最严重的一次地震。地震造成的遇难人数超过8万。汶川地震造成灾区房屋建筑和基础设施严重破坏,包括公路、铁路、航空三大交通系统严重破坏。交通受阻一度成为震后开展应急救援和恢复的关键问题。本文在地震现场调查的基础上,综述了汶川地震对交通系统的影响,总结了各交通系统的震后应急抢修情况。     

基于F-D曲线法的中国大陆地区地震灾害经济可接受风险研究

合理的地震灾害经济可接受风险水平可以有效管理防灾减灾的投入。基于1991～2020年中国大陆地区地震灾害经济损失数据,利用F-D曲线法(Frequency-Damage curve),建立不同震级(M_S<5.0、M_S5.0～5.9、M_S6.0～6.9和M_S≥7.0)和不同灾情等级(微灾、小灾、中灾、大灾和巨灾)的地震灾害经济可接受风险曲线,并以此为标准讨论30年间由地震产生直接经济损失事件的可接受风险等级。研究结果表明：中国大陆地区地震灾害造成0.020亿元直接经济损失的灾损率不超过1.29×10^-2/a为可接受经济风险,直接经济损失超过14.763亿元其灾损率为任意值均是不可接受经济风险。由此判断,30年间有18.07%的地震灾害属于不可接受经济风险事件。同理,不同震级和不同灾情等级地震灾害的可接受经济风险水平也被确定,并得到M_S<5.0、M_S5.0～5.9、M_S6.0～6.9和M_S     

中国西部典型房屋结构震害定量关系的初步研究

建筑物震害程度的判定是进行地震灾害损失评估的基础, 震害指数是建筑物震害程度的定量表示方式, 是房屋抗震性能的直观表现。 震害指数的研究对于震害预测和地震灾害损失评估都有重要的意义。 文中收集、 分析并处理了2001—2004年中国地震灾害损失现场调查与评估的详细资料, 以调查点为单位计算了各种结构类型房屋的平均震害指数, 建立了中国西部地区不同结构类型房屋的平均震害指数向未经加固的砖混和砖木结构房屋的平均震害指数转换的数学关系, 其结果对地震灾害及其损失的快速评估与现场评估具有一定的参考作用。     

A GIS-based earthquake damage assessment and settlement methodology

Earthquakes have a greater effect on society than most people think. These effects range from structural damages to economic impacts and fatalities. An earthquake only lasts for a few seconds and the aftershocks may continue for days, but the damage does continue for years. Residential site safety and earthquake damage assessment studies play a crucial role in developing reliable rehabilitation and development programs, improving preparedness and mitigating losses in urbanized areas. The extremely densely populated metropolis of Tehran, which totals of 7,768,561 for 22 districts (according to the 2006 population census), coupled with the fragility of houses and infrastructure, highlight the necessity of a reliable earthquake damage assessment based on essential datasets, such as building resistance attributes, building population, soil structures, streets network and hazardous facilities. This paper presents a GIS-based model for earthquake loss estimation for a district in Tehran, Iran. Damages to buildings were calculated only for the ground shaking effect of one of the region's most active faults, the Mosha Fault in a likely earthquake scenario. Earthquake intensity for each building location was estimated based on attenuation relation and the ratio of damage was obtained from customized fragility curves. Human casualties and street blockages caused by collapsed buildings were taken into account in this study, as well. Finally, accessibility verification found locations without clear passages for temporary settlements by buildings via open streets. The model was validated using the 2003 Bam earthquake damages. The proposed model enables the decision-makers to make more reliable decisions based on various spatial datasets before and after an earthquake occurs. The results of the earthquake application showed total losses as follows: structural damages reaching 64% of the building stock, a death rate of 33% of all the residents, a severe injury rate reaching 27% of the population and street closures upwards of 22% due to building collapse.