Damage costs for houses and farms as a function of intensity in the 1987 edgecumbe earthquake

This paper describes an analysis of damage costs to house and farm property in the M_s = 6.6 Edgecumbe, New Zealand earthquake of 2 March 1987. The study investigated damage ratios for dwellings, their contents and domestic motor vehicles. The damage costs were converted to damage ratios by dividing them by the total value of the relevant property in the intensity zones concerned. The mean values and statistical distributions of these damage ratios were then found, the lognormal distribution fitting very well. The mean damage ratio for house buildings at MM intensity IX was 0.080 and the mean damage ratios were generally smaller than previous studies had shown. The mean damage ratios were similar for buildings and contents from MM6 to MM9, but there was no correlation between building and contents damage on an individual basis.     

一种基于有限动态源的烈度估计方法

首先,基于地震烈度与震级和震中距或震源距的经验关系,考虑实际地震断层的有限性以及几何学和运动学特性,提出了一种基于有限动态源模型的烈度预估方法.然后,利用数值实验讨论了体现几何学和运动学特性的参数的作用以及断层的倾角和破裂速度的影响;最后,将这种方法应用于近年来发生的两次破坏性地震,讨论了这种方法的实用性与不足之处.在实时获取破裂过程图像成为可能的今天,用这种方法预估烈度对于震后救援十分重要.     

芦山7.0级地震单层砖柱排架厂房震害特征及抗震分析

单层砖柱排架厂房是我国中小企业生产用房的主要形式,目前此类结构仍广泛存在于经济欠发达的地区。历次地震震害资料表明,单层砖柱排架厂房在地震中比较容易损坏。本文通过对芦山地震中单层砖柱排架厂房的震害现场调查,总结了单层砖柱排架厂房的震害特征并分析其破坏原因;统计了几次地震中单层砖柱排架厂房的震害资料,给出了修正的未设防单层砖柱排架厂房地震易损性矩阵;最后,采用了逐步回归法,柱顶位移角法及模糊震害指数法分别对单层砖柱排架厂房进行震害预测,并将各种方法的震害预测结果与实际震害情况进行了对比分析。本文研究对认识该类结构的易损性、震害机理和抗震薄弱部位,指导抗震加固有着重要意义。     

1987年寻乌5.5级地震事件的回顾与启示

通过对1987年寻乌5.5级破坏性地震应急工作的回顾和总结。针对在此次地震应急工作中存在的问题和不足，提出在破坏性地震事件处理中改进有关工作的初步设想。以便提高各级政府及地震部门在破坏性地震发生时的应急处理能力。     

Accounting for directionality as a function of structural typology in performance‐based earthquake engineering design

For the seismic design of a structure, horizontal ground shaking is usually considered in two perpendicular directions, even though real horizontal ground motions are complex two‐dimensional phenomena that impose different demands at different orientations. While the issue of ground motion dependence on the orientation of the recording devices has been the focus of many significant developments during the last decade, the effects of directionality on the characteristics of the structure have received less attention. This work presents a proposal to calculate the probability of exceedance of elastic spectral displacements accounting for structural typology and illustrates its relevance by means of its application to two case‐study buildings. In order to ease its implementation in seismic design codes, a simplification is developed by means of a detailed statistical analysis of the results obtained using four sets of real hazard curves. The framework presented herein is considered to represent an important contribution to the field of performance‐based earthquake engineering, permitting improved treatment of directionality effects within seismic risk design and assessment. Copyright © 2016 John Wiley & Sons, Ltd.     

邢台地区设定地震事件烈度影响

通过邢台地区历史地震烈度资料分析,得到该地区烈度—频率灾害曲线及地震风险。以地震地质资料理论为基础,结合河北省城市活断层探测成果、地壳结构等资料,确定2个设定地震事件。采用复合震源模型,模拟合成强地面运动,并基于强地面运动模拟结果,分析邢台地区地震影响烈度,为今后该地区建筑物抗震设防、避难场所选址、震后救援以及地震保险风险评估提供参考依据。     

Site amplification effects as an explanation for the intensity anomaly in the Hanyuan Town during the Wenchuan M_w 7.9 earthquake

The Hanyuan Town is located approximately 200 km from the macro-epicenter of the great Wenchuan earthquake. However, it is within the only Intensity Ⅷ zone, surrounded by a region of Intensity Ⅵ. The objective of this study was to investigate this high-intensity anomaly with respect to the site amplifications in the Hanyuan Town. The base inputs were derived from the records at a nearby strong-motion station because no records were available from the town. The characteristics of the subsurface formations and their dynamic properties at a typical site in the town were obtained by drilling, field tests and laboratory tests. Seismic response and parametric sensitivity analyses of the site were conducted using Shake 91, and the results were compared with the provisions for rare earthquakes from the Chinese Code for Seismic Design of Buildings(GBJ11-89). The results showed that the average peak acceleration at the site during the Wenchuan earthquake is similar to the code-specified value under rare earthquakes, that the corresponding spectral accelerations for periods between approximately 0.35 and 0.75 s are significantly stronger than those specified by the code and that the average amplification factor at the site is significantly higher than the mean value of the site class. These findings indicate that the high-intensity anomaly in the town was primarily caused by site amplification effects from the unique structure of the soil strata.     

1987年寻乌地震前的地震活动性异常特征及其相关讨论

利用“八五”，“九五”地震预报攻关研究的成果。对1987年寻乌Ms5.5级地震前的地震活动性异常特征进行了再研究。结果表明，此次地震前出现小震活动空区，地震活动“增强-平静”，前兆性震群活动等多项明显的地震活动性异常。这些异常还表现出一些中期向短期过渡的特征。对将来主震的中短期预测具有一定的参考价值。     

云南盈江Ms5.8级地震和缅甸Ms7.2级地震预测总结及震后趋势分析

针对强震能否预测以及如何预测的科学难题,建立了孕震断层多锁固段脆性破裂理论与相关预测方法.结合作者前期研究成果--中缅边境地震区未来强震四要素预测结果,并与2011年3月云南盈江Ms5.8级地震、缅甸Ms7.2级地震比较,认为这两次地震都能被作者提出的理论方法提前预测,表明该理论方法能可靠地应用于中等强度预震和主震的预...     

张北-尚义地震震前阶段中小地震速度谱周期特征的研究

从 Duda 和 Nortmann 提出的谱震级定义出发,利用北京台网中小地震速度数字化记录资料,采用14组0.5倍频程滤波器组,其中心周期为:0.04s、0.06s、0.08s、0.12s、0.18s、0.28 s、0.40s、0.60s、0.96s、1.28s、2.40s、3.80s、6.20s、10.00s,分别计算了各中小地震的速度 谱综合因子f值,结果显示张北-尚义地震震前阶段中小地震的三分向速度谱卓越频率向高频 方向偏离,综合因子 f 值逐渐增加,且蓝地震的发生有向主震震中靠拢的趋势。同时,研究认为 综合因子 f 值可以量化蓝地震的定义。     

Recent development of the earthquake strong motion-intensity catalog and intensity prediction equations for Iran

This study aims to develop a new earthquake strong motion-intensity catalog as well as intensity prediction equations for Iran based on the available data. For this purpose, all the sites which had both recorded strong motion and intensity values throughout the region were first searched. Then, the data belonging to the 306 identified sites were processed, and the results were compiled as a new strong motion-intensity catalog. Based on this new catalog, two empirical equations between the values of intensity and the ground motion parameters (GMPs) for the Iranian earthquakes were calculated. At the first step, earthquake “intensity” was considered as a function of five independent GMPs including “Log (PHA),” “moment magnitude (M_W),” “distance to epicenter,” “site type,” and “duration,” and a multiple stepwise regression was calculated. Regarding the correlations between the parameters and the effectiveness coefficients of the predictors, the Log (PHA) was recognized as the most effective parameter on the earthquake “intensity,” while the parameter “site type” was removed from the equations since it was determines as the least significant variable. Then, at the second step, a simple ordinary least squares (OLS) regression was fitted only between the parameters intensity and the Log (PHA) which resulted in more over/underestimated intensity values comparing to the results of the multiple intensity-GMPs regression. However, for rapid response purposes, the simple OLS regression may be more useful comparing to the multiple regression due to its data availability and simplicity. In addition, according to 50 selected earthquakes, an empirical relation between the macroseismic intensity (I₀) and M_W was developed.     

Simulating earthquake ground motion at a site, for given intensity and uncertain source location

Following a companion article, ground motion acceleration time historiesduring earthquakes can be described as realizations of non-stationarystochastic processes with evolutionary frequency content and instantaneousintensity. The parameters characterizing those processes can be handled asuncertain variables with probabilistic distributions that depend on themagnitude of each seismic event and the corresponding source-to-sitedistance. Accordingly, the generation of finite samples of artificial groundmotion acceleration time histories for earthquakes of given intensities isformulated as a two-stage Monte Carlo simulation process. The first stageincludes the simulation of samples of sets of the parameters of thestochastic process models of earthquake ground motion. The second stageincludes the simulation of the time histories themselves, given theparameters of the associated stochastic process model. In order to accountfor the dependence of the probability distribution of the latter parameterson magnitude and source-to-site distance, the joint conditional probabilitydistribution of these variables must be obtained for a given value of theground motion intensity. This is achieved by resorting to Bayes Theoremabout the probabilities of alternate assumptions.Two options for the conditional simulation of ground motion time historiesare presented. The more refined option makes use of all the informationabout the conditional distribution of magnitude and distance for thepurpose of simulating values of the statistical parameters of the groundmotion stochastic process models. The second option considers allprobabilities concentrated at the most likely combination of magnitude anddistance for each of the seismic sources that contribute significantly to theseismic hazard at the site of interest.     

几种仪器烈度算法在汶川地震与芦山地震中的可靠性比较

破坏性地震发生后, 特别是在通信中断的情况下, 利用仪器烈度快速估计地震动强度(烈度)的分布情况, 可为开展最有效的地震应急救援提供决策依据. 该文介绍了现有的几种仪器烈度算法, 并利用汶川地震与芦山地震中获得的强震加速度记录对各种算法的可靠性进行了比较. 结果表明, 在这两次地震中只利用地震动峰值参数确定仪器烈度的算法可靠性较低, 而考虑反应谱特性的算法可靠性更高. 在未得到更多强震数据的检验前, 建议采用袁一凡提出的仪器烈度算法, 或利用谱烈度值确定仪器烈度的算法, 或利用加速度反应谱值确定仪器烈度的算法.     

烈度仪用于地震预警的可靠性研究——以高雄MS6.8地震为例

以2016年2月6日我国台湾高雄M_S6.8地震中烈度仪观测网的实际记录为研究对象,通过对烈度仪台站的震相捡拾结果精度、峰值地震动衰减关系适用性、预警震级计算结果准确性等3方面的对比分析,研究了烈度仪用于地震预警时的优势和可靠性,并讨论了可能存在的问题和风险.研究结果表明:对于震中附近具有较高信噪比的烈度仪台站,采用现有震相捡拾方法即可获得较准确的震相到时信息;现有的地震动衰减关系并不完全适用于烈度仪台网,直接应用这些关系式时存在一定风险;基于密集布设的烈度仪观测台网,在较短时间即可获取大量信息,采用已有预警震级估算方法的计算结果有较高的准确性.      

无人机倾斜摄影技术在地震烈度评估中的应用——以九寨沟7.0级地震为例

以九寨沟7.0级地震为例,通过阐述无人机倾斜摄影技术的相关原理,说明该技术在地震烈度评估中的应用价值。结果表明,使用无人机倾斜摄影技术不仅能够直观地、全方位地展示震害信息,同时,还能对裂缝、滑坡等几何信息进行量测,为烈度评估等提供更加精确的信息。     

美国西部地震烈度衰减规律

在国家和地区地震动区划和重大工程的地震安全性评价工作中，区域地震动衰减规律的确定是重要环节，而借用法是目前常用的建立区域地震动衰减的方法。我国借用法通常都把美国西部作为参考地区，但一般都采用调整美国学者已有烈度衰减规律的办法确定美国西部烈度衰减规律。本文讨论美国西部已有烈度衰减规律，并直接采用美国西部烈度调查资料建立烈度衰减规律，结果可供我国工程地震工作者参考。     

从阿尔及利亚地震结构震害看我国闽南地区结构的抗震能力

2003年5月22日阿尔及利亚Ms6．9级地震发生,笔者参加了震后救援工作和科考工作。本文介绍和分析了阿尔及利亚的结构特点及其破坏特征,且较为深入地分析了其破坏的原因。以此为鉴,初步分析了我国闽南地区房屋结构的整体抗震能力,提出应对之策以防患于未然。     

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.     

Fault mechanisms and tectonic implication of the 1985–1987 earthquake sequence in south-western Ethiopia

Integrated inversions of short-period P, broadband P, and long-period P &s waves are done for fault mechanisms, focal depths, seismic moments, and source-time functions from the largest four earthquakes of the 1985 and 1987 earthquake sequence in south-western Ethiopia. These earthquakes had similar normal-faulting mechanisms. The general trends of the fault planes follow the Main Ethiopian Rift which is in agreement with foreshock-aftershock distribution, surface breaks and geology. Despite the morphological discontinuity of the Main Ethiopian Rift at its southern tip, the mode of deformation of the continental crust under study shows its extension southward. There are no significant strike-slip components trending NW–SE in all the mechanisms which would have been associated with the Aswa Fault Zone in southern Sudan or Anza Rift in northern Kenya. We also infer that the relatively broad fracture zone at the southern extreme of the Main Ethiopian Rift demonstrates the early stage of the break-up between the Nubia and Somalia plates in comparison with the Main Ethiopian Rift proper and the Afar Depression. The main shock of the sequence (M_w = 6.3) ruptured at a depth of 6.8 km, shallower than expected since the depth of earthquakes generally increase southward from the Afar Depression. The shallow depth of earthquake occurrence is supported by surface deformations with an overall trend in the direction of the Main Ethiopian Rift.     

Post-earthquake estimates of different ground motion intensity measures for the 2012 Emilia earthquake

Estimates of the earthquake ground motion intensity over a geographical area have multiple uses, that is, emergency management, civil protection and seismic fragility assessment. In particular, with reference to fragility assessment, it is of interest to have estimates of the values of different ground-motion intensity measures in order to correlate them with the observed damage. To this purpose, the present paper uses a procedure recently proposed in the literature to estimate the ground-motion intensity for the 2012 Emilia mainshocks, considering different ground motion intensity measures and directionality effects. Ground motion prediction equations based on different site effect models, and spatial correlation models are calibrated for the Emilia earthquakes. The paper discusses the accuracy of the shakemaps obtained using the different soil effect models considered and presents the obtained shakemaps as supplementary material. The procedure presented in the paper is aimed at providing ground motion intensity values for seismic fragility assessment and is not intended as a tool to estimate shakemaps for rapid emergency assessment.