Correlation of JMA instrumental seismic intensity with strong motion parameters

The Japan Meteorological Agency (JMA) seismic intensity (I_JMA) has been used as a measure of strong shaking for many years in Japan, and it necessitates to know the correlation between the JMA seismic intensity and other strong motion indices, e.g. Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), and Spectrum Intensity (SI). In this study, two strong motion data sets were selected; in which, the first set consists of 879 three‐components non‐liquefied records selected from 13 major earthquake events that occurred in Japan, the United States, and Taiwan, and the second set consists of 17 liquefied records selected from 7 major earthquake events that occurred in Japan and the United States. The JMA seismic intensity and other ground motion indices were calculated using the selected data sets. The relationships between the JMA seismic intensity and PGA, PGV, and SI were then derived performing a two‐stage linear regression analysis. Results from the analysis show that the JMA instrumental seismic intensity shows higher correlation with SI than PGA or PGV, and it shows the highest correlation with the parameters such as the combination of PGA and SI or the product of PGA and SI. The obtained relationships are also compared with the ones obtained by other studies, which may be useful for the disaster management agencies in Japan and deployment of new SI‐sensors that monitor both PGA and SI. Copyright © 2002 John Wiley & Sons, Ltd.     

Rating damage potential of ground motion records

In this study, a total of 115,246 ground motions recorded during earthquakes of Moment magnitudes ranging from M_w 5.0 to M_w 9.0 are analyzed statistically. A total of 21 ground motion parameters characterising the recorded acceleration time histories are used in the analysis. Classification of these parameters through statistical correlation is reported and a parameter called "distance from zero-amplitude axis," or d_Z-A, is formulated in the principal component space. The ability for d_Z-A to rate the damage potentials of strong motion records is evaluated through correlation of d_Z-A with Japan Meteorological Agency(JMA) instrumental seismic intensities. This parameter can be used to rate damage potential of any strong motion record irrespective of the magnitude and location of the earthquake. It can also be used in selecting ground motion records of appropriate damage potential in seismic design and probabilistic analysis.     

A simplified method of constructing fragility curves for highway bridges

Fragility curves are found to be useful tools for predicting the extent of probable damage. They show the probability of highway structure damage as a function of strong motion parameters, and they allow the estimation of a level of damage probability for a known ground motion index. In this study, an analytical approach was adopted to develop the fragility curves for highway bridges based on numerical simulation. Four typical RC bridge piers and two RC bridge structures were considered, of which one was a non‐isolated system and the other was an isolated system, and they were designed according to the seismic design code in Japan. From a total of 250 strong motion records, selected from Japan, the United States, and Taiwan, non‐linear time history analyses were performed, and the damage indices for the bridge structures were obtained. Using the damage indices and ground motion parameters, fragility curves for the four bridge piers and the two bridge structures were constructed assuming a lognormal distribution. It was found that there was a significant effect on the fragility curves due to the variation of structural parameters. The relationship between the fragility curve parameters and the over‐strength ratio of the structures was also obtained by performing a linear regression analysis. It was observed that the fragility curve parameters showed a strong correlation with the over‐strength ratio of the structures. Based on the observed correlation between the fragility curve parameters and the over‐strength ratio of the structures, a simplified method was developed to construct the fragility curves for highway bridges using 30 non‐isolated bridge models. The simplified method may be a very useful tool to construct the fragility curves for non‐isolated highway bridges in Japan, which fall within the same group and have similar characteristics. Copyright © 2003 John Wiley & Sons, Ltd.     

2012年唐山4.8级地震强震动记录特征及场地相关特性分析

2012年5月28日河北省唐山市古冶区与滦县交界发生4.8级地震, 国家强震动台网中心在河北、 天津和北京的94个强震动台站记录到了本次地震的加速度。 本文给出了获取记录的强震动台站分布及强震动记录结果, 统计了强震动记录数量随震中距的变化, 给出了3个较小震中距台站记录到的加速度时程; 绘制了空间地震动峰值加速度等值线图及周期0.2 s、 2.0 s加速度反应谱值的等值线, 发现峰值加速度等值线与长周期加速度反应谱等值线极值分布具有明显地域差异, 分析认为是由于厚沉积层对长周期地震动具有放大作用造成的。 通过强震动记录与适用于本区的三个衰减关系对比, 分析了此次地震的峰值加速度衰减特征, 同时研究了周期0.2 s、 2.0 s加速度反应谱值的衰减特征, 周期2.0 s反应谱值随震中距的衰减与衰减关系能较好地对应, 然而在震中距100～130 km沉积层较厚的集中地区, 表现出了实际记录较衰减关系值偏大的现象, 认为同样是由于厚沉积层对地震动加速度反应谱长周期的放大作用导致的。 研究了震中距差别不大的情况下, 场地类型与沉积层厚度对反应谱特征周期的影响, 对比基岩台站与软弱地基土层台站的强震动记录反应谱, 发现软弱土层台站的土层对地震动有一定的放大作用, 导致中长周期地震动被放大, 对比位于沉积层较薄的隆起区台站与位于沉积层较厚的凹陷区台站强震动记录反应谱, 发现厚的沉积层不仅对反应谱长周期有放大的作用, 同时也会使得反应谱特征周期值变大。     

A ground motion prediction equation for JMA instrumental seismic intensity for shallow crustal earthquakes in active tectonic regimes

The JMA (Japan Meteorological Agency) seismic intensity scale has been used in Japan as a measure of earthquake ground shaking effects since 1949. It has traditionally been assessed after an earthquake based on the judgment of JMA officials. In 1996 the scale was revised as an instrumental seismic intensity measure (I_JMA) that could be used to rapidly assess the expected damage after an earthquake without having to conduct a survey. Since its revision, Japanese researchers have developed several ground motion prediction equations (GMPEs) for I_JMA using Japanese ground motion data. In this paper, we develop a new empirical GMPE for I_JMA based on the strong motion database and functional forms used to develop similar GMPEs for peak response parameters as part of the PEER (Pacific Earthquake Engineering Research Center) Next Generation Attenuation (NGA) project. We consider this relationship to be valid for shallow crustal earthquakes in active tectonic regimes for moment magnitudes ( M ) ranging from 5.0 up to 7.5–8.5 (depending on fault mechanism) and rupture distances ranging from 0 to 200 km. A comparison of this GMPE with relationships developed by Japanese researchers for crustal and shallow subduction earthquakes shows relatively good agreement among all of the relationships at M 7.0 but relatively poor agreement at small magnitudes. Our GMPE predicts the highest intensities at small magnitudes, which together with research on other ground motion parameters, indicates that it provides conservative or upwardly biased estimates of I_JMA for M <5.5. Copyright © 2010 John Wiley & Sons, Ltd.     

Application of microtremor measurements to the estimation of earthquake ground motions in Kushiro city during the Kushiro-Oki earthquake of 15 january 1993

Microtremor measurements were conducted in Kushiro City, Hokkaido Island of Japan. The thickness of alluvial deposits in the central area of Kushiro City abruptly changes from 0 to 80 m. Predominant ground motion at a microtremor measuring site is represented by the spectral ratio, the ratio of Fourier amplitude spectrum of microtremor in the horizontal direction to that in the vertical direction. The peak frequency of the spectral ratio corresponds well to the predominant frequency estimated from the thickness of alluvial layer at each site. Based on a hypothesis that the spectral ratio can be regarded identical with a half of the amplification factor from diluvial bed rock to the ground surface, the strong ground motion due to the Kushiro-oki earthquake at each site is estimated. The method of estimation is verified by the comparison of the synthesized accelerogram with the recorded one at West Port of Kushiro. The results satisfactorily explain major damages and vibrations felt in Kushiro City during the earthquake.     

基于实测记录分析场地因素对海底地震动特性影响

目前基于海底实测记录的分析发现海底与陆地地震动特性存在明显差异,但难以进一步确定海底地震动特性的影响因素。在以往研究的基础上对比同次地震中相邻海底台站间地震动特性的差异,并分析造成差异的原因。以日本K-NET地震台网中6个海底强震台站及其相邻不同场地条件陆地台站监测的8次强震记录为研究对象,通过分析强震记录的峰值加速度、水平放大系数谱、竖向与水平反应谱的比谱等,对比分析不同海底台站地震动的特性,以及海底台站与相邻不同场地条件陆地台站地震动特性的差别。研究发现：（1）海底与陆地竖向地震动存在明显差异;（2）不同海底台站间地震动特性亦存在较大差异和明显的规律性,海底场地条件、地形等场地因素对海底地震动特性的影响较大;（3）海底水平向地震动反应谱的特征周期较大,谱特性介于陆地中硬土与软土场地间。     

一种实时场地校正方法及其在地震预警中的应用

地震预警系统对地震数据处理的实时性要求极高。其系统数据来源除布设在基岩的测震台站外,还有大量非基岩场地的强震动台站和地震烈度仪台站,其场地影响不容忽视。为了考虑震级估算和地震动场预测中的场地影响,需实时对各种场地条件下的地震波形进行校正。目前处理一般使用某个标量来表征场地放大效应。本文采用一种实时的场地校正方法,首先计算目标场地与参考场地的谱比,然后通过最小二乘法、双线性变换将谱比转化为因果递归的无限冲激响应(IIR)时域滤波器,之后可以应用该滤波器进行实时场地校正。该方法考虑了场地放大系数的频率依赖性,相比于标量校正提高了准确度。应用我国四川和日本部分强震动台站记录,验证并讨论了这种实时场地校正方法在地震预警中的应用效果。     

表层沉积物特性对地震地面运动的影响研究

建立包含震源、沉积盆地和表层低速沉积层的二维模型,采用交错网格有限差分/伪谱混合方法求解地震波传播,讨论沉积层厚度和速度对地震地面运动的作用。结果表明:沉积层内产生的地震波的多重反射以及转换会引起地面运动持续时间的延长,它们的相干叠加会造成地面运动峰值的放大;随着沉积层速度的增加,多重反射与转换波的能量减小,地面运动持续时间减小,但是不同速度或者不同厚度的低速层模型均显示出一致的地面运动峰值放大特征。结果说明,在包含震源、沉积盆地和沉积层的模型中,沉积层对地面运动的作用机理更复杂。在实际应用中有必要同时考虑这些因素的综合作用。     

盆地对三分量地震动持时的影响初探

利用关东盆地及其周边KiK-net台网井上台站记录的2004—2017年15次中强地震（矩震级为5.1～6.9级）构建三分量记录显著持时Ds_5-95数据库。针对该数据库,基于残差分析方法和3种水平向地震动持时参数预测方程,计算并给出事件间残差和事件内残差及其随不同类别参数的变化。在此基础上,初步探讨了水平向地震动持时预测方程应用于预测竖向地震动持时的可行性及盆地对三分量地震动持时的影响。研究结果表明,对于震源距和场地V_S30相当的情况,盆地内台站持时普遍大于盆地外台站持时,盆地内、外台站竖向地震动持时均大于水平向地震动持时;3种预测方程均可实现对盆地外台站水平向地震动Ds_5-95的合理估计,但在一定程度上低估了盆地内台站的水平向地震动Ds_5-95;3种预测方程均无法直接应用于竖向地震动持时预测。     

HORIZONTAL-TO-VERTICAL SPECTRUM RATIO OF EARTHQUAKE GROUND MOTION FOR SITE CHARACTERIZATION

Nakamura's method, which uses a horizontal-to-vertical Fourier spectrum ratio of microtremor, has become popular to determine the predominant period and amplification of a site. In this study, this method is extended for earthquake ground motion recordings using new strong motion data recorded by JMA-87-type accelerometers. From the analysis of these accelerograms, horizontal-to-vertical Fourier spectrum ratios of a site for different earthquakes are also found to be stable irrespective of magnitude, distance and depth. To establish this fact, attenuation relations of velocity response spectra for horizontal and vertical components are derived for three damping ratios (0, 2 and 5 per cent) using the JMA data. Then the horizontal-to-vertical ratios of the velocity response spectra are obtained. The results show that the horizontal and vertical velocity response spectra are dependent on magnitude, distance and depth, but that their ratios are almost independent of magnitude, distance and depth. However, since the current data set consists of mostly intermediate to far field data, this observation should be limited to records of these distance ranges. Introducing station coefficients, representing site amplification, to this relation yields the value comparable to the horizontal-to-vertical Fourier spectrum ratio at a specific site. The stability of the spectrum ratio is explained by the transfer function between the ground surface and stiff-soil outcrop due to S-wave propagation. These results suggest that site amplification characteristics can be evaluated by one-point two-component surface recordings of earthquake ground motion, in a similar manner as proposed by Nakamura for microtremor. © 1997 by John Wiley & Sons, Ltd.     

基于一致可靠度的地震动记录样本容量确定方法研究

确定地震动输入样本容量是开展结构动力地震反应分析的重要环节,目前国内外关于地震动输入样本容量的讨论往往忽略或尚难以定量考虑结构地震反应估计的可靠度水平。以一实际钢筋混凝土框架结构为例,首先分析在大样本地震动作用下结构非线性地震反应的统计特征,研究估计结构地震反应时取样本最大值和平均值的差异,然后借助于假设检验分析结构地震反应的概率分布模型,给出基于一致可靠度的地震动样本容量确定方法,并对比分析单周期点、多周期点、谱值匹配调整地震动及人工合成地震动对样本容量需求的影响,为保证在小样本地震动输入下结构地震反应估计值满足给定可靠度和容许误差提供分析方法和判断依据。本文方法适应于定量确定不同结构类型和不同地震强度水平下的地震动样本容量需求,对建筑结构抗震性能评估及设计规范研究有一定意义。     

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.     

福州盆地强地面运动特征的有限元数值模拟

区域性地震波强地面运动的量化数值模拟分析结果可以用来指导城市规划建设,并在防震减灾中发挥重要作用. 本文采用有限元数值模拟方法来模拟由地震激发的区域地震波强地面运动过程,并得到地表峰值速度和加速度的分布特征.考虑到福州是东南沿海的重要省会城市,其明显的盆地结构特征使它很容易遭受强地震灾害的影响. 因此本文以福州盆地为主要研究对象,假定盆地的主要断层某一位置在未来可能发生灾害性地震,则该地震会激发地震波的强地面运动,并由于地形、沉积层等主要影响,在盆地内部发生放大.通过对地震波传播过程的数值模拟和后处理分析,给出了该盆地的地表峰值位移、峰值速度和峰值加速度分布图谱.该图谱可为未来的福州城市规划和抗震减灾提供定量科学参考依据.     

Study on the severest real ground motion for seismic design and analysis

How to select the adequate real strong earthquake ground motion for seismic analysis and design of trucures is an essential problem in earthquake engineering research and practice.In the paper the concept of the severest design ground motion is proposed and a method is developed for comparing the severity of the recorded strong ground motions.By using this method the severest earthquake ground motions are selected out as seismic inputs to the structures to be designed from a database that consists of more than five thousand significant strong ground moton records collected over the world.The selected severest ground motions are very likely to be able to drive the structures to their critical response and thereby result in the highest damage potential.It is noted that for different structures with diffferent predominant natural periods and at different sites where structures are located the severest design ground motions are usually different.Finally.two examples are illustrated to demonstrate the rationality of the concept and the reliability of the selected design motion.     

特征地震强地面运动参数衰减公式拟合

计算机仿真模拟设定地震断层动态破裂传播和近断层强地表运动响应的结果表明, 对于特征地震而言,近断层附近的地表运动特征与断层破裂传播的方向性有着强烈的依赖关系. 当场地（观测点）至断层的距离给定时,正向于破裂传播方向的场地（场地A）的地表质点运动（位移、速度、加速度）,远远大于震中附近（场地B）和反向于破裂传播方向的场地（场地C）的地表质点运动,而且沿断层垂直分量所辐射的SH波的传播起到了主导作用. 对应于场地A,B和C,统计分析结果表明,峰值加速度的几何平均值之比为2.15:1.5:1, 而且各自的均方差分别为0.12, 0.11和0.13. 如果将所得的研究结果应用于概率地震危险性分析中,对于较低的年超越频度,近断层附近的地表峰值加速度的估算值可下降15%~30%. 因此,考虑到断层破裂传播方向性对地表运动的影响,区域衰减曲线的回归分析模型应该给予恰当的修正.      

Towards a new reference ground motion prediction equation for Italy: update of the Sabetta–Pugliese (1996)

A revised Italian strong motion archive has become available since July 2007, including all the records of the strongest events occurred from 1972 to 2004. It contains the uncorrected and corrected accelerograms and the metadata relevant to seismic events, recording stations and instruments added after a careful revision. The availability of this archive allowed us to perform a first step towards an update of the reference ground motion prediction equations for Italy, which were evaluated by Sabetta and Pugliese in (Bull Seismol Soc Am 77:1491–1513, 1987), for peak ground acceleration and velocity, and subsequently extended to the 5% damped pseudovelocity response spectra in 1996. A subset with the 27 major earthquakes occurred in Italy from 1972 to 2002, in the magnitude range 4.6–6.9, was extracted and 235 good quality waveforms were selected, recorded at distances up to 183 km. The goodness of fit of the Sabetta and Pugliese (Bull Seismol Soc Am 86:337–352, 1996) model was explored using two independent statistical approaches (Spudich et al. Bull Seismol Soc Am 89:1156–1170, 1999 and Scherbaum et al. Bull Seismol Soc Am 94:2164–2185, 2004). The results obtained show that the Sabetta and Pugliese (Bull Seismol Soc Am 77:1491–1513, 1987) does not adequately fit the new strong-motion data set, for its small standard deviation and its non-zero bias. In particular, the most noteworthy result is that the Sabetta and Pugliese (Bull Seismol Soc Am 77:1491–1513, 1987) over-predicts peak ground acceleration and velocity at rock sites. New coefficients for the prediction of horizontal peak ground acceleration, peak ground velocity and acceleration response spectra, adopting the same functional form in Sabetta and Pugliese (Bull Seismol Soc Am 77:1491–1513, 1987), were then evaluated in order to fit the new data set. This paper illustrates the steps made to update the existing ground motion prediction equations for Italy, discusses their limitations and provides the basis for future developments.     

应用动态复合震源模型模拟汶川Mw7.9地震强地面运动

2008年5月12日中国汶川地区发生Mw7.9地震,震中位置103.4°E,31.0°N.主要发震断层空间展布长达300多公里,由南西方向到北东方向呈现明显的分段性,汶川一映秀段逆冲为主兼有少量的右旋走滑分量;安县一北川段为逆冲一右旋走滑的断层错动;青川段以右旋走滑为主兼有少量逆冲分量.采用改进后的复合震源强地面运动预...     

基于特征分类排序的典型海底地震动记录研究

面向海域工程抗震设计及评估对海底地震动的需求,基于日本相模湾海域K-NET的ETMC海底强震动记录,根据震级、震中距选取面向工程输入的949组地震动记录数据库。在考虑震源类型差异的基础上,对地震动峰值、持时、频谱等参数进行分析,通过反应谱、Arias烈度等指标描述典型海底地震动特征。根据峰值加速度、显著持时等强度指标对海底地震动记录进行排序,给出基于不同地震动特征分类下的典型地震动记录。推荐的海底地震动可为考虑不同结构需求参数的典型海域工程结构时程分析提供输入地震动。     

强地震动估计和地震危险性评定

本文介绍了近几年获取的强震记录中显示出的地震动特征，诸如近断裂的破裂方向性效应、上盘效应、影响地震波传播的地壳波导效应、沉积盆地的放大效应和盆地边缘效应；归纳了强地震动估计的三种方法，简要综述了经验性衰减模型、预测强地震动的随机法和宽频带格林函数法；讨论了估计活断层引起的地震动所应把握的要点。