A new empirical equation of shear wave velocity to predict the different peak surface accelerations for Jakarta city

Site condition and bedrock depth play important roles in the determination of peak surface acceleration(PSA)values by earthquake motions.The soil parameters of shear wave velocity(Vs)and standard penetration test-number(N)value for Jakarta city are available up to 100 m below the Earth’s surface even though the typical depths to bedrock are in excess of 100 m.This study referred to the base motion peak ground acceleration(PGA)values of 0.100 g,0.218 g and 0.378 g to predict the PSA values using the Nonlinear Earthquake site Response Analysis(NERA)to analyse a simulated dataset for the bedrock depths of 100 m,200 m,300 m,400 m and 500 m with conditioned by clayey and sandy soils.A new empirical equation of Vs=102.48 N0.297(m/s)was proposed to calculate the values of Vsused as an input parameter in the NERA programme for the prediction of seismic wave propagation.The results showed that the PSA values are dependent on the amplitude of seismic waves,depths of bedrock and the local site conditions.Changes in the PSA values from 41.0%to 51.5%and from 46.1%to 79.8%for the bedrocks overlain by sand,from 20.0%to 42.1%and from 45.9%to 58.8%for the bedrocks overlain by clay with increasing of bedrock depths from 200 m to 300 m and from 400 m to 500 m,respectively,were predicted for a 2500-year return period earthquake.Decreases in the PSA values by 41.0%,51.5%,46.1%,79.8%for the bedrocks overlain by sand and by 20.0%,42.1%,45.9%,58.8%for the bedrocks overlain by clay were predicted for a 2500-year return period earthquake due to the bedrock depth changes of 200 m,300 m,400 m,500 m.Large-magnitude earthquake of Jakarta city has a significant effect on an increase or a decrease of the PSA value with depth of bedrock and may cause the vibration damage to buildings and other constructions on the ground.The analysis of the PSA value and PSA ratio influenced by the PGA value,bedrock depth and local soil conditions will make a contribution to the design of earthquake-safe building for Jakarta city in the future.

Attenuation of peak ground accelerations from the great Wenchuan earthquake

Over 800 accelerograms recorded by 272 ground-level stations during the Wenchuan earthquake are used to analyze the influence of rupture distance, local site conditions and azimuth on peak ground accelerations （PGAs）. To achieve a better understanding of the characteristics of ground motions, the spatial distributions of the EW, NS and UD components of PGAs are obtained. Comparisons between the EW and NS components, the fault-normal and fault-parallel components, and the vertical and horizontal components of PGAs are performed, and the regression formula of the vertical-to-horizontal ratio of PGAs is developed. The attenuation relationship of peak horizontal accelerations （PHAs） is compared with several contemporary attenuation relationships. In addition, an analysis of residuals is conducted to identify the potential effects of rupture distance, azimuth and site conditions on the observed values of PHAs. The analysis focuses on medium-hard soil site conditions, as they provided most of the data used in this study.

Comparison of the cumulative absolute velocity and acceleration peak value based on Wenchuan earthquake data

This paper discusses and presents the cumulative absolute velocity （CAV） parameters of the Wenchuan earthquake. Additionally, the CAV calculated from recorded data for the earthquake is compared to the peak ground acceleration（PGA）, based on a brief analysis of background information. Accordingly, the paper studied the relationship between the CAV and PGA, and 3 CAV/PGA ratio charts were obtained in three different sub-directions. Linear and polynomial fitting operations were then used to analyze the potential discipline and characteristics in these directions. Finally, in the study, we investigated the applicability of using the CAV parameter for earthquake observation systems, and the CAV parameter was paired with the currently used PGA to provide earthquake observers and emergency responders with a theoretical basis.

基于监测台网加速度信号分析的上海周边区域地震影响评价

2021年11月至2023年8月期间,上海市周边区域共发生了5次有感地震,分别为江苏盐城市大丰区海域5.0级、江苏常州市天宁区4.2级、黄海海域4.8级、上海市青浦区3.1级和山东德州市平原县5.5级地震,同济大学监测台网的4个测站捕获了这5次地震的场地和典型结构加速度信号,分析了各次地震作用下场地和典型结构的加速度信号的峰值及持时,探讨了各次地震信号的反应谱特征,对照设计反应谱曲线的第一特征段和第二特征段,对这5次周边区域地震对上海市的影响进行评价。

顺倾及反倾层状碎裂结构斜坡地震反应的大型振动台试验研究

西南艰险山区分布着大量的不同倾向的层状碎裂结构斜坡,地震作用下极易发生崩塌、滑坡等灾害,对在建的川藏铁路造成严重威胁。通过大型振动台模型试验,研究了强震条件下顺倾、反倾层状碎裂结构斜坡的动力响应、失稳破坏模式以及能量传递规律。试验结果表明:反倾斜坡的抗震性能显著优于顺倾斜坡;顺倾斜坡的破坏模式主要为拉裂-剪切-隆起-滑移型破坏,反倾斜坡的破坏模式主要为拉伸-弯曲-倾倒-崩塌型破坏;反倾斜坡的自振频率高于顺倾斜坡,顺倾斜坡的自振频率随震级的增加而逐渐降低,而反倾斜坡的自振频率在地震波幅值为0.4g~0.7g时出现反复震荡现象;顺倾斜坡存在明显的高程放大效应和趋表效应,反倾斜坡存在高程放大效应,其内部的加速度响应大于坡表。边际谱识别显示:顺倾斜坡的边际谱幅值(peak of marginal spectrum amplitude,简称PMSA)突变在坡腰上部最显著,说明该位置附近地震波的能量损失最大,反映出顺倾斜坡在坡腰上部附近形成了滑动破坏面;反倾斜坡的PMSA在坡肩处降低得最为显著,反映出坡肩部位损伤最为严重,易发生局部崩塌破坏。分析结果与试验现象能够较好地吻合,进一步揭示了不同结构类型层状碎裂结构斜坡在强震作用下的动力响应与失稳破坏模式,为川藏铁路的安全建设提供了依据。

震源机制类型对近场峰值加速度(PGA)分布的影响——以唐山和汶川震区为例

利用首都圈强震台网比较密集的数字地震记录,研究2003年4月发生在唐山震区的2次4级地震。利用布设在四川、甘肃、陕西的强震台网和临时强震台网的资料,研究2008年7月和8月发生在四川汶川的2次6级地震。得到正断层和走向滑动断层、逆冲断层和走向滑动断层的地震近场PGA分布的差异。结果表明,这种差异是显著的。不仅大震的PGA近场分布复杂,中小地震也是如此。经频谱分析发现,这种影响出现差异的地震波频率较低,城市化的建筑向高层大型发展,其自振周期相应较长。近直立走向滑动地震的PGA高值区沿断层对称分布,而正断层和逆断层则集中在断层上盘,这对于破坏性地震应急救援中力量、物资的投入有借鉴意义。

谱强度SI和地震动峰值加速度PGA参数在高铁列车地震预警中的应用

为了降低没有破坏性的高频小震对高铁地震报警的干扰,引入谱强度SI参数作为报警参数,分析其在高铁地震报警中的适用性。研究发现低频振动对SI的影响比高频振动大,对于高铁线路附近的高频小震,SI参数能有效的排除,但对于破坏性不大的远震大震可能会引发报警,从而产生误报现象,影响高铁列车运行效率。为了降低SI在破坏性小的远震大震中的误报率,本文引入PGA与SI作为报警参数。最后给出了不同时速下基于PGA与SI联合报警的阈值供参考。

Vertical-to-horizontal response spectral ratio for offshore ground motions:Analysis and simplified design equation

In order to study the differences in vertical component between onshore and offshore motions,the vertical-to-horizontal peak ground acceleration ratio(V/H PGA ratio) and vertical-to-horizontal response spectral ratio(V/H) were investigated using the ground motion recordings from the K-NET network and the seafloor earthquake measuring system(SEMS).The results indicate that the vertical component of offshore motions is lower than that of onshore motions.The V/H PGA ratio of acceleration time histories at offshore stations is about 50%of the ratio at onshore stations.The V/H for offshore ground motions is lower than that for onshore motions,especially for periods less than 0.8 s.Furthermore,based on the results in statistical analysis for offshore recordings in the K-NET,the simplified V/H design equations for offshore motions in minor and moderate earthquakes are proposed for seismic analysis of offshore structures.

The Analysis of Accelerograms for the Earthquake Resistant Design of Structures

In this paper, the analysis of ground motions (displacements, velocities and accelerations) has been performed focused to the seismic design. The relationships between the peak ground acceleration (PGA), the peak ground velocity (PGV), the peak ground displacement (PGD) and the bracketed duration, with the earthquake magnitude, are presented and their validity and applicability for seismic design is discussed. Finally, the dominant periods of the ground motions (displacement, velocity and acceleration) are obtained from their Fourier Spectrum. Their validity and applicability for the seismic design is discussed also. The results presented in this paper show that the relationships that exist between the important parameters: PGA, PGV, PGD and duration;and the earthquake magnitude, allow the prediction of the values for these parameters, in terms of the magnitude for future strong motions. These predictions can be very useful for seismic design. Particularly, the prediction of the magnitude associated to the critical acceleration, because the earthquakes with magnitude greater than this critical magnitude can produce serious damages in a structure (even its collapsing). The application of the relationships obtained in this paper must be very careful, because these equations are dependent on the source area, location and type of structure. The dominant periods of the ground motions (displacement, velocity and acceleration) that are computed and presented in this paper, are also important parameters for the seismic design, because recent studies have shown that the earthquake shaking is more destructive on structures having a natural period around some of these dominant periods. These parameters must also be handled with caution, because they show dependence with the source area, location and type of structure.

汶川地震诱发滑坡与地震动峰值加速度对应关系研究

利用汶川地震获得的地震动记录及峰值加速度数据和收集整理的近3000个崩滑点数据,对汶川地震诱发滑坡与地震动峰值加速度之间的对应关系进行研究,得到如下认识:(1)地震动峰值加速度与地震诱发崩滑之间存在非常明显的正相关性,随峰值加速度增加,地震滑坡灾害也逐渐严重。(2)在龙门山震区存在0.2g的峰值加速度分界线,大于此值时,地震滑坡灾害比较严重。(3)整个区域峰值加速度的下限为0.05～0.07g,小于此值时,诱发滑坡的可能性很小。(4)不同地质区域对应斜坡临界加速度有所不同,一般在0.05～0.15g之间变化,平均为0.1g,说明震区斜坡承受地震的水平较差;峰值加速度超过局部场地斜坡临界加速度后,诱发滑坡的可能性增加。得到的峰值加速度研究结果与其他研究结果较为一致,表明利用地震动参数研究地震滑坡具有很好的一致性。依据峰值加速度与地震滑坡的对应关系,可以对震后滑坡灾害作快速评估,也可以将其应用到地震滑坡灾害预测/区划工作中,与地震动峰值加速度区划形成很好的衔接。

地震烈度和地震动参数相关性研究进展及讨论

地震烈度直观反映震害轻重程度,而根据地震动记录推测烈度可大大加速烈度评定进程。另外我国目前抗震设计还处于烈度和地震动参数并用时期,需要两者关系,因此研究烈度与地震动参数(峰值加速度/PGA,峰值速度/PGV)的关系十分必要。本文介绍了中外各国两者相关性研究的历史沿革以及研究成果,并进一步对所有研究成果进行了对比分析及讨论。

最大峰值加速度与有效峰值加速度的大小比例关系及影响因素探讨

分别以最大峰值加速度(以下简称PGA)和有效峰值加速度(以下简称EPA)为参数,对金沙江流域上12个工程场点进行了地震危险性分析,得到了各个场点在不同的年超越概率下的基岩PGA和EPA值。通过对PGA、EPA值比较分析认为:PGA与EPA值的大小比例关系主要受年超越概率大小的影响,当年超越概率较大时,表现为PGA>EPA;当年超越概率较小时,PGA与EPA的比例关系还与场点周围的潜源分布形式及潜源的震级上限的大小有关,不同的年超越概率、不同的潜源分布形式和震级上限,可使PGA>EPA,也可使PGA<EPA。

梁式桥抗震设计的弹塑性位移反应谱

合理选取四类场地320条强震记录,研究地震动特性及恢复力模型动力参数对弹塑性位移谱与残余位移谱影响。结果表明,给出某一标准设防烈度的弹塑性反应谱,其它设防烈度下弹塑性反应谱可据PGA设防烈度与PGA标准烈度比值调整获得;可忽略屈服后刚度比对弹塑性位移谱影响,但应选择偏于保守的屈服后刚度比统计残余位移谱,由此建立的残余位移谱只适用短周期、低延性一般规则桥梁中、低矮桥墩的抗震设计;阻尼比与位移延性比为影响弹塑性位移谱及残余位移谱重要因素,阻尼比增大会减少桥梁非弹性变形及震后残余位移。基于该结果建立适用于我国梁式桥抗震设计的弹塑性及残余位移谱,为考虑残余位移影响的梁式桥基于性能的抗震设计提供重要参考依据。

土的动剪切模量非线性特性对地震动的影响研究

通过一维等效线性化方法研究土的动剪切模量非线性特性对土层地震反应的影响,主要分析动剪切模量比与剪应变关系曲线以及最大动剪切模量对反应谱特征周期和地表加速度峰值的影响。结果表明,对于小震和中震,土的动剪切模量比和最大动剪切模量对反应谱特征周期略有影响,对地表加速度峰值影响并不明显;但对于大震,对反应谱特征周期和地表加速度峰值影响较大,随着动剪切模量比和最大动剪切模量的增大,反应谱特征周期减小,地表加速度峰值增大,土层越厚其影响越大。二者对比结果表明,强震下土的动剪切模量比与剪应变关系曲线对地震动的影响程度要比最大动剪切模量对地震动的影响大得多,说明强震下土的动剪切模量比与剪应变关系曲线对土层地震反应会产生更显著影响。

表层土结构对地表地震动的影响研究

场地覆盖土层的结构特别是近地表土层结构的变化对地表地震动的影响很大,针对表层土结构的变化对地表地震动的影响进行研究。根据场地实际钻孔资料,选取和构造了199个场地计算剖面,利用工程上广泛应用的一维等效线性化波动分析方法,计算了不同场地类别(Ⅰ、Ⅱ、Ⅲ类)在3个典型地震动时程、但不同幅值输入情况下地表的峰值加速度的变化情况。通过对计算结果的分析,总结了表层土厚度的变化和剪切波速的变化对不同场地地表峰值加速度的规律性影响。

地表水下渗对典型黄土场地地震效应的影响

近年来,地表水下渗对工程地质灾害的影响逐渐被人们所关注,但是其对黄土场地地震动的影响还没有引起足够的重视。因此,选取典型黄土场地,分析了地表水下渗对地表加速度反应峰值及加速度反应谱的影响,旨在研究地表水下渗对黄土场地地面运动的影响规律。结果表明:随着地表水的不断下渗,地表地震峰值加速度及土层地震动放大作用都有减小趋势,地表水的存在一定程度上对地震动具有减震作用;但场地的特征周期都有增的趋势,反应谱平台范围越来越宽,使得地面上固有周期处于反应谱平台范围内的建筑都有较大的反应,尤其是与原始剖面(没有地表水)相比,地表水的存在对场地特征周期的放大作用最大可达1.5倍左右,这使得地面上更多的建筑都会有较大的反应。

国际上两种典型土层地震反应分析程序对比研究

土层地震反应分析方法分为频域与时域两大类,目前国际上最好的一维程序为SHAKE2000与DEEPSOIL,但二者的适用性和比较情况尚不得知。构造了符合我国规范的4种类别场地,对14个场地在3条地震动输入和3个烈度下总共82组工况进行对比计算,研究二者计算出的地表峰值加速度、反应谱和剪应变的异同。结果表明:二者差异大小与场地类别、输入PGA和输入地震动的频率分布有关,其中场地类别起主要作用,其他因素影响较小;只有在Ⅰ类场地下二者差异可忽略,其他类别场地存在差异,深软场地差异十分显著;虽然DEEPSOIL在计算反应谱高频部分表现优于SHAKE2000,但无论地表加速度峰值还是整体反应谱都要逊于后者,特别是对Ⅲ类场地和Ⅳ类场地情况;DEEPSOIL计算得到的土体剪应变普遍大于SHAKE2000,在软土场地表现十分显著,很多工况结果达到了不合理的程度,这应是其表现逊色的原因;在Ⅲ类和Ⅳ类场地下,两程序很多计算结果与现有认识相差很大。其结果为了解掌握土层地震反应分析方法的国际现有水平及今后方法改进提供了一定基础。

复杂斜坡动力响应特征分析

深切谷坡浅表部卸荷裂隙发育,风化强烈,致使浅表层成为非连续介质,出现介质性质差异,地震动响应由此变得复杂。通过对青川东山斜坡地震动监测数据进行分析,并结合适用于分析岩质边坡运动过程的非连续变形分析(DDA)方法对青川东山斜坡动力响应特征进行数值模拟,揭示了震中距、高程、震级、地形以及"丁"字形山体等因素对地震波峰值加速度(PGA)放大的影响。结果表明:垂直山脊方向以及高程较高时的地震波峰值加速度放大倍数较大,可达6.12倍;在地形突出部位,地震波亦能得到一定程度的放大,放大倍数可达3.3倍;在"丁"字形山脊结合部位,PGA放大倍数会出现一定程度的减小。

基于现行规范场地划分标准的地震动峰值加速度衰减关系研究

文章搜集了美国西部近几年场地钻孔资料和近几年的强震记录,根据钻孔资料把强震记录按照我国《建筑抗震设计规范》(GB 50011-2010)中的规定进行场地分类,利用这些强震记录建立了适合我国场地的地震动峰值衰减关系。在衰减关系模型中考虑到了震级饱和和近场距离饱和特性,统计得到了Ⅰ、Ⅱ、Ⅲ类场地的地震动峰值加速度的衰减关系并分析了其特点。通过将Ⅰ类场地地震动PGA的衰减关系和其他研究的基岩场地衰减关系对比,可以看出第Ⅰ类场地得到的水平与竖向PGA衰减曲线和其他研究的基本一致。由此说明只要场地分类相同,使用各地区同类场地的强震记录进行地震动参数研究是可行的。研究结果为我国各类场地的PGA的估计提供了依据。

面向地下结构的最优地震动峰值指标随埋深变化规律

选取了50条实际地震动,采用一维场地等效线性化方法分别对均匀半空间场地和成层半空间场地进行地震响应分析,同时选择效益性作为判别标准来探究最优地震动峰值指标(峰值加速度PGA,峰值速度PGV,峰值位移PGD)随埋深变化的规律.研究结果表明:对于选取的两类场地,最优地震动峰值指标均随埋深的改变而变化,埋深浅时PGA效益性最优,随着埋深的增加,效益性最优逐渐由PGA转变至PGV;PGA与PGV转折的交点位置随场地剪切波速的不同而不同,且该转折交点位置与场地剪切波速呈线性相关.