共查询到17条相似文献，搜索用时 187 毫秒
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2021年2月13日日本福岛县东部海域(Off-Fukushima)发生的MW7.1地震是目前世界最大的海底观测系统——日本海沟地震和海啸海底观测网(S-net)——迄今为止记录到最大的俯冲带地震.为认识海底地震动并探究海陆差异,本文介绍了S-net海域台网及其数据处理的特殊性和必要性,分析了Off-Fukushima地震的地震动幅值、频谱和持时特征,比较了海底与陆地震动衰减特性的异同,对比了近海岸埋置台站、近海沟未埋台站及陆地台站地震动的差异,并与俯冲带地震动模型(GMM)进行了比较.结果表明：Off-Fukushima地震海底水平向PGV和周期大于0.5 s的加速度反应谱值显著大于陆地记录;相比陆地,海底动力放大系数谱向长周期方向偏移,表明海底记录长周期成分更丰富;受到海水的抑制作用,海底记录V/H反应谱比值小于陆地记录;由于海底记录与陆地GMM在路径和场地方面存在差异,水平向PGA及反应谱的残差分布出现明显偏移;海底近海岸埋置台站与近海沟未埋台站的地震动特征存在系统性差异,水平向差异很可能与海底地形有关,而竖向可能受到布设方式对台站与海底耦合程度的影响.本文... 相似文献
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局部场地条件是决定场地地震动强度和频谱的重要因素，基于强震动和脉动记录的统计分析，获取表征场地条件影响的特征参数已成为确定工程场地设计地震动的较经济和实用方法，特别是对于大范围或难以开展现场勘测的工程场地。利用日本KiK-net台网强震动记录计算分析了台站场地地震动水平/竖向谱比（HVSR）与地表/基底谱比（SBSR）的差异，揭示SBSR/HVSR与HVSR呈对数线性分布的统计特征，并给出其定量关系，据此提出表征场地对地震动影响的修正水平/竖向谱比法。修正水平/竖向谱比法具有仅需地表观测记录的优势，并进一步考虑了场地竖向地震效应对水平/竖向谱比法精度的影响，更能合理地表征场地对地震动的影响。 相似文献
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为考查远场地震动的场地相关性并评价一些场地特性分析方法的适用性,采用不同方法对汶川地震山东省12个远场台站的强震记录进行了分析.选取台站分别位于按建筑抗震设计规范(CBC)场地划分中的Ⅰ—Ⅲ类场地上.地震动记录的分析方法包括傅里叶幅值谱法,地震反应谱法,水平与竖向谱比率法,参考点谱比率法,以及尾波分析等.结果表明,按傅里叶幅值谱法,地震反应谱法,水平与竖向谱比法计算得到的卓越周期均远大于台站场地的卓越周期,不同方法得到的结果之间也有较大差别,且主要反映长周期地震动的卓越频率;参考点谱比率法的结果未反映地震动的卓越周期,也与场地的卓越周期差别较大;对完整记录尾波分析所得的结果比较接近场地的卓越周期.希望本文能为考虑远场地震作用时设计谱的建立,以及场地特性估计时地震动分析方法的选取提供参考依据. 相似文献
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为基于谱比方法研究海底地震动场地效应,选取日本DONET1台网的20个海底台站2014—2021年记录的1634组地震数据,对其进行筛选和处理后,利用水平与竖向谱比（HVSR）方法考虑不同布设对海底5组节点台站（KMA、KMB、KMC、KMD、KME）谱比特征的影响。研究结果表明:KMA与KME节点台站具有相似的场地特征,KMB与KMD节点台站分散布置在2种场地,KMC节点台站场地与其他节点均不相似,这与长期地质调查结果相似;海底台站谱比曲线呈多峰值现象,其中KMB、KMC、KMD分组台站利用HVSR方法识别的主频变异性较高,KMA、KME分组台站主频较稳定;相同地形条件下,布设方式相同的海底台站谱比曲线随频率分布相似,海底复杂场地条件下,采用装沙沉底方式布置的台站识别场地条件时出现偏差;海底复杂因素对掩埋沉箱方式布设的台站谱比曲线的影响主要集中在频率<5 Hz的低频处;海底复杂因素对未埋入海底台站谱比曲线的影响主要集中在频率为5—10 Hz的高频处。研究结果可为海底地震动场地效应研究提供参考。 相似文献
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通过对水口水电站重力坝强震反应台站在古田地震中获取的强震反应观测资料进行信噪比、反应谱和功率谱分析,得到如下结论:①大坝在0.7～15 Hz频率段的振动特性较为可信;②坝基和自由场输入地震动富于高频,峰值加速度反应谱存在较大差异;③坝基输入地震动存在差异性,建议今后此类大坝抗震设计时考虑多点地震动输入;④单个卓越频率携带的能量对反应谱影响不大,反应谱是和输入地震动总能量相关的;⑤坝体刚度较大,此次地震中还处于线弹性状态。初步了解了强震记录的地震动特性和大坝结构的抗震性能,对认识水库地震近场地震动特性和重力坝地震反应有一定的参考意义。 相似文献
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显著的竖向地震动是近断层地震动区别于远场地震动的重要特征之一,为更合理地确定竖向地震动作用,研究了近断层区域竖向地震动的反应谱特征及其与水平向反应谱比值的影响因素.首先,选取1952—1999年世界范围内震级在M5.4—7.6之间的18次地震的地震动记录,研究竖向地震加速度反应谱及其与水平向加速度反应谱比值特征;然后统计分析了断层距、场地条件、震级以及断层机制对竖向与水平向加速度反应谱比的影响.结果表明,一般情况下竖向加速度具有更丰富的短周期分量,并且竖向加速度反应谱衰减较慢;断层距在20km以内的近断层区域、软弱土层场地、中等震级地震和逆断层大震级中长周期范围等条件下,具有较大的竖向与水平向加速度反应谱比值;在近断层区域的结构抗震设计中应充分考虑竖向地震动的影响. 相似文献
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随着强震台网的密布及观测记录的增加,为研究各类局部场地地震反应预测模型的合理性提供了有效的参考依据,也使利用强震记录及场地条件研究地震动特征成为可能。选取场地地质参数资料和地震记录数据齐全的日本小田原（Ashigara Valley）盲测试验场地,通过对比不同地震动输入方式及场地反应分析模型,研究地震动特征,分析现有模型的优劣。基于1990年8月5日M5.1强震事件的地表基岩记录和地下基岩地震记录,采用地下台强震记录直接输入、地表基岩台强震记录减半为基底地震动输入、地表基岩台强震记录反演为基底地震动输入作为3种基岩地震动输入。基于局部场地条件分别建立一维等效线性模型、二维黏弹性模型及二维时域等效线性化模型等工程中常用的场地数值分析模型,进行局部场地地震反应分析,预测该盲测场地的地表地震动特征,并与对应的实测强震记录结果进行对比,分析不同基岩地震动输入方式对预测地震动特征及地表土层反应谱特征的影响,重点分析地震动输入、土体非线性、场地横向不均匀性及几何与非线性特征共同作用等因素对地表地震动特征的影响,以期为地表地震动的合理预测提供参考。 相似文献
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The effect of seawater on vertical ground motions is studied via a theoretical method and then actual offshore ground motion records are analyzed using a statistical method. A theoretical analysis of the effect of seawater on incident plane P and SV waves at ocean bottom indicate that on one hand, the affected frequency range of vertical ground motions is prominent due to P wave resonance in the water layer if the impedance ratio between the seawater and the underlying medium is large, but it is greatly suppressed if the impedance ratio is small; on the other hand, for the ocean bottom interface model selected herein, vertical ground motions consisting of mostly P waves are more easily affected by seawater than those dominated by SV waves. The statistical analysis of engineering parameters of offshore ground motion records indicate that:(1) Under the infl uence of softer surface soil at the seafl oor, both horizontal and vertical spectral accelerations of offshore motions are exaggerated at long period components, which leads to the peak spectral values moving to a longer period.(2) The spectral ratios(V/H) of offshore ground motions are much smaller than onshore ground motions near the P wave resonant frequencies in the water layer; and as the period becomes larger, the effect of seawater becomes smaller, which leads to a similar V/H at intermediate periods(near 2 s). These results are consistent with the conclusions of Boore and Smith(1999), but the V/H of offshore motion may be smaller than the onshore ground motions at longer periods(more than 5 s). 相似文献
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This paper aimed to examine the site dependence and evaluate the methods for site analysis of far-source ground motions. This was achieved through the examination of frequency content estimated by different methods based on strong ground motions recorded at twelve far-source stations in Shandong province during the Wenchuan earthquake. The stations were located in sites with soil profiles ranging from code classes Ⅰ to Ⅲ. Approaches used included the Fourier amplitude spectrum (FAS), the earthquake response spectrum (ERS), the spectral ratio between the horizontal and the vertical components (H/V), the spectral ratio between the spectra at the site and at a reference site (SRRS), and coda wave analysis (CWA). Results showed that major periods of these ground motions obtained by FAS, ERS and H/V ratio methods were all evidently larger than site dominant periods; the periods were also different from each other and mainly reflected the frequency content of long period components. Prominent periods obtained by the SRRS approach neither illuminated the long period aspect nor efficiently determined site features of the motions. The CWA resulted in a period close to site period for stations with good quality recordings. The results obtained in this study will be useful for the evaluation of far-source effect in constructing seismic design spectra and in selecting methods for ground motion site analysis. 相似文献
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This paper presents a novel approach to model and simulate the multi-support depth-varying seismic motions (MDSMs) within heterogeneous offshore and onshore sites. Based on 1D wave propagation theory, the three-dimensional ground motion transfer functions on the surface or within an offshore or onshore site are derived by considering the effects of seawater and porous soils on the propagation of seismic P waves. Moreover, the depth-varying and spatial variation properties of seismic ground motions are considered in the ground motion simulation. Using the obtained transfer functions at any locations within a site, the offshore or onshore depth-varying seismic motions are stochastically simulated based on the spectral representation method (SRM). The traditional approaches for simulating spatially varying ground motions are improved and extended to generate MDSMs within multiple offshore and onshore sites. The simulation results show that the PSD functions and coherency losses of the generated MDSMs are compatible with respective target values, which fully validates the effectiveness of the proposed simulation method. The synthesized MDSMs can provide strong support for the precise seismic response prediction and performance-based design of both offshore and onshore large-span engineering structures. 相似文献
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A wide variety of near-fault strong ground motion records were collected from various tectonic environments worldwide and were used to study the peak value ratio and response spectrum ratio of the vertical to horizontal component of ground motion, focusing on the effect of earthquake magnitude, site conditions, pulse duration, and statistical component. The results show that both the peak value ratio and response spectrum ratio are larger than the 2/3 value prescribed in existing seismic codes, and the relationship between the vertical and horizontal ground motions is comparatively intricate. In addition, the effect of the near-fault ground motions on bridge performance is analyzed, considering both the material nonlinear characteristics and the P~? effect. 相似文献
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Turkey was struck by two major events on August 17th and November 12th, 1999. Named Kocaeli (Mw=7.4) and Düzce (Mw=7.2) earthquakes, respectively, the two earthquakes provided the most extensive strong ground motion data set ever recorded in Turkey. The strong motion stations operated by the General Directorate of Disaster Affairs, the Kandilli Observatory and Earthquake Research Institute of Bogazici University and Istanbul Technical University have produced at least 27 strong motion records for the Kocaeli earthquake within 200 km of the fault. Kocaeli earthquake has generated six motions within 20 km of the fault adding significantly to the near-field database of ground motions for Mw>=7.0 strike–slip earthquakes. The paper discusses available strong motion data, studies their attenuation characteristics, analyses time domain, as well as spectral properties such as spectral accelerations with special emphasis on fault normal and fault parallel components and the elastic attenuation parameter, kappa. A simulation of the Kocaeli earthquake using code FINSIM is also presented. 相似文献
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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。 相似文献