Dependence of correlations between spectral accelerations at multiple periods on magnitude and distance

In this paper, the dependence of correlations between spectral accelerations at multiple periods on magnitude (M) and distance (R) has been investigated. For this purpose, a relatively large dataset of ground motion records (GMRs), containing 1551 records with a wide range of seismic characteristics, was selected. It is shown that the difference in the correlation coefficient is statistically meaningful when the general GMR dataset is divided into two subsets based on an arbitrary M or R. The observed difference is more meaningful in the case of magnitude when compared with distance. The general dataset of GMRs was then divided into four separate subsets based on optimum values of M and R, so that the four obtained subsets were given the greatest dissimilarity in terms of the correlation coefficients. The correlation coefficients between spectral accelerations at multiple periods were calculated in the case of the four subsets and compared with the available correlations in the literature. The conditional mean spectrum was also calculated by means of the conventional correlation coefficients, as well as by using the proposed M and R dependent correlation coefficients. The results show that, despite the commonly available findings in the literature, this dependence is significant and should not be neglected in the conditional spectra calculation process. Copyright © 2013 John Wiley & Sons, Ltd.     

用Matlab软件内部函数校正强震记录的探讨

在标准化结构反应谱时,需要准确地确定地面地震动峰值。而在地震期间,测量地面运动时采集到的地震动加速度时程数据由于种种原因存在基线漂移问题,导致所测数据不能真实反映地面运动．由此难以确定真实地面运动峰值。通过对地震动加速度数据拟合,根据拟合后的数据计算地震速度及位移．并将计算结果分别与利用已有基线修正方法求得的速度及位移进行对比．从而确定最佳拟合次数,消除基线漂移造成影响。研究结果表明,经12次拟合修正地震动加速度求得的地震动位移峰值可用于相对位移反应谱标准化。     

用强震记录检验深厚土层小应变下一维等效线性化土层地震反应

本文以强震记录为基础,通过土层地震反应计算得到了地表加速度与加速度反应谱,对比研究了由强震记录得到的地表加速度以及由地表加速度得到的与土层地震反应相同阻尼下的加速度反应谱.结果表明:在高频段与中频段,用一维等效线性化计算得到的土层地震反应加速度值与反应谱值比地表实测得到的加速度记录值与加速度反应谱值偏低;但在低频段,计...     

Simulation of synthetic ground motions for specified earthquake and site characteristics

A method for generating a suite of synthetic ground motion time‐histories for specified earthquake and site characteristics defining a design scenario is presented. The method employs a parameterized stochastic model that is based on a modulated, filtered white‐noise process. The model parameters characterize the evolving intensity, predominant frequency, and bandwidth of the acceleration time‐history, and can be identified by matching the statistics of the model to the statistics of a target‐recorded accelerogram. Sample ‘observations’ of the parameters are obtained by fitting the model to a subset of the NGA database for far‐field strong ground motion records on firm ground. Using this sample, predictive equations are developed for the model parameters in terms of the faulting mechanism, earthquake magnitude, source‐to‐site distance, and the site shear‐wave velocity. For any specified set of these earthquake and site characteristics, sets of the model parameters are generated, which are in turn used in the stochastic model to generate the ensemble of synthetic ground motions. The resulting synthetic acceleration as well as corresponding velocity and displacement time‐histories capture the main features of real earthquake ground motions, including the intensity, duration, spectral content, and peak values. Furthermore, the statistics of their resulting elastic response spectra closely agree with both the median and the variability of response spectra of recorded ground motions, as reflected in the existing prediction equations based on the NGA database. The proposed method can be used in seismic design and analysis in conjunction with or instead of recorded ground motions. Copyright © 2010 John Wiley & Sons, Ltd.     

Ground motion modelling in Tehran based on the stochastic method

This paper presents the development of a seismological model for the Tehran area. This modelling approach, which was originally developed in Eastern North America, has been used successfully in other parts of the world including Australia and China for simulating accelerograms and elastic response spectra. Parameters required for input into the model were inferred from seismological and geological information obtained locally. The attenuation properties of the earth crust were derived from the analysis of accelerogram records that had been collated from within the region in a previous study. In modelling local modifications of seismic waves in the upper crust, shear-wave velocity profiles have been constructed in accordance with the power law. Information inferred from micro-zonation studies (for near-surface conditions) and from measurements of teleseismic P-waves reflected from the deeper crusts as reported in the literature has been used to constrain parameters in the power-law relationships. This method of obtaining amplification factors for the upper crust distinguishes this study from earlier studies in the Tehran area (in which site amplification factors were inferred from the H/V ratio of the recorded ground motions). The regional specific seismological model so constructed from the study enabled accelerograms to be simulated and elastic response spectra calculated for a series of magnitude–distance combinations. Importantly, elastic response spectra calculated from the simulated accelerograms have been compared with those calculated from accelerograms recorded from earthquakes with magnitudes ranging between M6.3 and M7.4. The peak ground velocity values calculated from the simulated accelerograms have also been correlated with values inferred from macro-seismic intensity data of 17 historical earthquakes with magnitudes varying between 5.4 and 7.7 and with distances varying between 40 and 230 km. This paper forms part of the long-term strategy of the authors of applying modern techniques for modelling the attenuation behaviour of earthquakes in countries which are lacking in instrumental data of earthquakes.     

Ground motion prediction equation considering combined dataset of recorded and simulated ground motions

Himalayan region is one of the most active seismic regions in the world and many researchers have highlighted the possibility of great seismic event in the near future due to seismic gap. Seismic hazard analysis and microzonation of highly populated places in the region are mandatory in a regional scale. Region specific Ground Motion Predictive Equation (GMPE) is an important input in the seismic hazard analysis for macro- and micro-zonation studies. Few GMPEs developed in India are based on the recorded data and are applicable for a particular range of magnitudes and distances. This paper focuses on the development of a new GMPE for the Himalayan region considering both the recorded and simulated earthquakes of moment magnitude 5.3–8.7. The Finite Fault simulation model has been used for the ground motion simulation considering region specific seismotectonic parameters from the past earthquakes and source models. Simulated acceleration time histories and response spectra are compared with available records. In the absence of a large number of recorded data, simulations have been performed at unavailable locations by adopting Apparent Stations concept. Earthquakes recorded up to 2007 have been used for the development of new GMPE and earthquakes records after 2007 are used to validate new GMPE. Proposed GMPE matched very well with recorded data and also with other highly ranked GMPEs developed elsewhere and applicable for the region. Comparison of response spectra also have shown good agreement with recorded earthquake data. Quantitative analysis of residuals for the proposed GMPE and region specific GMPEs to predict Nepal–India 2011 earthquake of Mw of 5.7 records values shows that the proposed GMPE predicts Peak ground acceleration and spectral acceleration for entire distance and period range with lower percent residual when compared to exiting region specific GMPEs.     

汶川地震不同场地反应谱平台值统计分析

加速度反应谱平台值表征地震动的强度特性,场地条件是影响反应谱平台值的一个重要因素.本文选取6组同一地区断层距相近而场地条件不同的强震记录,对其标准化的加速度反应谱形状及平台值进行分析;并以汶川地震中173个有详细地勘场地上的强震记录为基础,统计分析了不同场地类别和断层距区间内的加速度反应谱平台值.本文研究结果显示,场地条件对加速度反应谱平台值有较大影响,随着场地变软,加速度反应谱平台值增大.本文定义了场地影响系数,计算并给出了不同地面峰值加速度对应的场地影响系数.     

Effects of moment magnitude,site conditions and closest distance on damping modification factors

Damping modification factors (DMF) are used to adjust response spectral values corresponding to damping 5% of critical to other damping levels. Ground motions recorded are orderly grouped according to moment magnitude, site conditions and closest distance. Near-fault motion records with closest distance closer than 10 km are not included in this paper. Based on the classification, the effects of the three seismological parameters on the median DMF are investigated. Consequently, the influence of site class reduces with increasing earthquake magnitude, and the effect of closest distance generally can be neglected with closest distance closer than 100 km except for rock sites. Except for soft soil sites, moment magnitude has a more significant effect than closest distance and site conditions, and the median DMF from acceleration spectra are most sensitive to seismological parameters. For soft soil sites, the median DMF only vary a little with moment magnitude and closest distance.     

Wavelet-Hilbert transform-based simulation of pulse-like ground motion

In nonlinear dynamic structural analysis, a suite of pulse-like ground motions is required for the performance-based design of structures near active faults. The dissimilarity in the amplitude and frequency content of the earthquake time series referred to nonstationary properties in temporal and spectral, respectively. An approach is proposed based on the nonstationary properties of the far-field records and the seismological information in an event for simulating pulse-like records. The pulse-like earthquake time history is estimated via the superposition of the residual part of the earthquake with the estimated pulse. The wavelet-based Hilbert transform is utilized to characterize the nonstationary properties, the instantaneous amplitude, and frequencies of far-field records to model residual part. The effects of near-fault and pulse are estimated based on the seismological properties of the region. The validation of the procedure is indicated by comparing simulated time-series, response spectra, and Arias intensity with recorded pulse-like records in two different earthquakes in California; the M_w 6.7 1994 Northridge and the M_w 6.5 1979 Imperial valley.

     

基于工程特性的主余震型地震动降维模拟

余震是由主震孕育而来,两者之间存在着一定的关联性,如何构造主余震型地震动模型,是工程结构抗震分析的基础。着眼于地震动的工程特性,根据主余震之间的峰值加速度、强震持时、场地卓越频率等要素,分别建立主震和余震自身的演变功率谱模型,基于非平稳随机过程的谱表示,通过引入随机函数降维模拟方法,实现仅用三个基本随机变量即可精确模拟主余震型地震动过程。研究表明,采用该降维模拟方法的效率和精度均满足工程需求,且与实测主余震型地震动记录的反应谱和幅值谱拟合一致,验证该模型与方法的优越性,为工程结构在主余震型随机地震作用下的抗震分析提供有效途径。     

Broadband ground motion simulation using a hybrid approach of the May 21, 2021 M7.4 earthquake in Maduo,Qinghai, China

In this study, the broadband ground motions of the 2021 M7.4 Maduo earthquake were simulated to overcome the scarcity of ground motion recordings and the low resolution of macroseismic intensity map in sparsely populated high-altitude regions. The simulation was conducted with a hybrid methodology, combining a stochastic high-frequency simulation with a low-frequency ground motion simulation, from the regional 1-D velocity structure model and the Wang WM et al. (2022) source rupture model, respectively. We found that the three-component waveforms simulated for specific stations matched the waveforms recorded at those stations, in terms of amplitude, duration, and frequency content. The validation results demonstrate the ability of the hybrid simulation method to reproduce the main characteristics of the observed ground motions for the 2021 Maduo earthquake over a broad frequency range. Our simulations suggest that the official map of macroseismic intensity tends to overestimate shaking by one intensity unit. Comparisons of simulations with empirical ground motion models indicate generally good consistency between the simulated and empirically predicted intensity measures. The high-frequency components of ground motions were found to be more prominent, while the low-frequency components were not, which is unexpected for large earthquakes. Our simulations provide valuable insight into the effects of source complexity on the level and variability of the resulting ground motions. The acceleration and velocity time histories and corresponding response spectra were provided for selected representative sites where no records were available. The simulated results have important implications for evaluating the performance of engineering structures in the epicentral regions of this earthquake and for estimating seismic hazards in the Tibetan regions where no strong ground motion records are available for large earthquakes.     

以反应谱和功率谱密度函数表征的强震运动的统计特性

文中利用我国海城和唐山地震１９０条强震记录和美国西部１３８条强震记录研究了以反应谱和功率谱密度函数表征的强震运动的统计特性。反应谱用最大地面加速度归一化，即表为谱放大系数，功率谱密度函数用金井清谱描述。文中研究了参数的统计值和依赖性，以及谱放大系数和金井清谱参数与场地条件、震源和震中距等之间的相关性，分析比较了中美两国强震运动谱的统计特性，并对我国地震工程应用的强震运动谱的统计参数值的选取提出了建议。     

用随机方法模拟唐山7.1级余震地震动场

在系统介绍用随机方法模拟地震动的基础上,用该方法模拟了唐山7.1级余震地震动场。模拟结果表明,唐山地区发生MS7.1级余震时,该地区产生了强烈的地震动,很多区域加速度峰值超过400cm/s2,地震断层面长65km,宽13.5km,地震过程中断层面的平均滑动为1.08m。模拟与记录的地震动持时符合得不好,其原因是随机方法中的经验关系大都是在美国大陆得到的,所以建议加强中国大陆相应的地震动经验关系的研究,使随机方法能更好地适用于中国大陆。尽管如此,由于用随机方法模拟的地震动峰值和反应谱与记录符合得比较好,这些模拟结果可以作为建筑物抗震设防的地震动输入。     

一种深厚覆盖层场地地震动参数的确定方法

基于欧美规范确定了坐落在深厚覆盖层上KH抽水蓄能电站上、下库场地基本运行和最大设计地震动峰值加速度、反应谱和时程等动参数。首先依据场地区域地震烈度区划图、特征周期区划图和依据场地地质地震条件选取的5条种子实测地震动确定场地基岩输入加速度时程、峰值加速度和设计反应谱,进而基于各土层地质参数和一维弹性波传播模拟程序确定覆盖层表面的平均峰值加速度、平均反应谱和5条地震动时程,对所得到的平均反应谱和峰值加速度进行光滑处理后确定可用于各建筑物结构抗震设计的地震动参数,包括覆盖层表面水平向动力响应加速度时程、峰值加速度和设计反应谱。该方法可较好地保留输入地震动的真实动力特性,如持时、相位和频率等,为我国规范中建议的确定场地地震动参数的方法提供有益的补充。     

Statistical Characteristics of Strong Ground Motion Specified by Response Spectrum and Power Spectral Density Function

The statistical characteristics of strong ground motion specified by response spectrum and power spectral density function are studied using 190 strong-motion records of the Haicheng and Tangshan earthquakes in China and 138 earthquakes in the western United States.The response spectrum is normalized by the peak ground acceleration(i.e.,represented as spectral magnification factor),and the power spectral density function is described by the Kanai-Tajimi spectrum.The statistics and dependence of parameters are evaluated,and correlations between the spectral magnification factor or Kanai-Tajimi spectral parameters and the site condition,epicentral distance,or local magnitude are investigated.The statistical characteristics of spectra China and the U.S.A.are compared.Based on the results obtained the values of the statistics on spectral parameters for earthquake engineering applications in China are suggested.     

A study of response spectra for different geological conditions in Gujarat,India

In this study, the effect of ground geology on the acceleration response spectra is studied at 32 sites in Gujarat, India. The sites are grouped into Proterozoic, Mesozoic, Tertiary and Quaternary. The normalized acceleration response spectra at 5% damping of 407 strong ground motions (horizontal and vertical components) recorded at these sites varying in magnitude from 3.0 to 5.7 are determined. The study shows that the shape of the acceleration response spectra is influenced by the regional geology and local site conditions. The peak of maximum horizontal spectral amplification is between 0.03 and 0.05 s in Proterozoic formations, 0.06 and 0.10 s in Mesozoic formations, 0.06 and 0.08 s in Tertiary and 0.12 s in Quaternary formations. The maximum vertical spectral acceleration is at 0.025 s in Proterozoic, 0.07 s in Mesozoic, 0.05 s in Tertiary and 0.10 s in Quaternary formations. The average acceleration amplification factor in all the geological formations is between 2.5 and 3.0 both in horizontal and vertical components. It has been observed that acceleration response spectra at sites having same geological formations are also influenced by local site conditions. The study shows that the acceleration response spectrum in the current Indian code applicable for the entire country underestimates the seismic forces at hard-rock sites and overestimates at soft-soil sites. Using recorded strong motion data with Mw ranging from 3.5 to 5.7, an attenuation relationship is developed at six periods to predict geometric mean of horizontal spectral amplitudes for rock and soil sites. The spectral amplitudes predicted with the attenuation relationship match well with the observed one within statistical limits for hypocentral distances less than 200 km.     

GROUND MOTION CHARACTERISTICS OF GAOYOU-BAOYING M4.9 EARTHQUAKE

An M4.9 earthquake occurred at the junction of Gaoyou and Baoying on July 20, 2012. In this paper, 43 sets of strong motion records of the main shock are analyzed. With these data, we analyzed the characteristics of the peak ground motion value, attenuation relation, duration and acceleration response spectrum. We draw the peak acceleration contour map of the region near the epicenter. The contour line is smooth and the trend of long axis is northwest-southeast. Distribution of peak acceleration of the observed records is basically consistent with the real intensity distribution. Compared with the predicted result based on the seismic attenuation relation proposed by Yu Yanxiang and Wang Suyunon for eastern China and the Fifth-generation ground motion zonation map, the horizontal PGA and PGV of Gaoyou-Baoying earthquake are higher than the predicted results that are based on the model of Fifth-generation ground motion zonation map, while the PGV is similar with the predicted results which are based on Yu Yanxiang and Wang Suyun's model. We regressively analyzed the spatial-temporal change curves of the two types of relative ground motion durations. Compared with the predicted results proposed by Bommer et al. (2009) based on the NGA strong motion records, the durations of all the three components of this earthquake are higher. 10 typical recordings' acceleration response spectra with 5% damping are calculated, their peak periods are around 0.1~0.3s. The acceleration response spectrum of the station 32BYT, which has the largest amplitude, is considerably larger than the Chinese code design spectra, while it becomes notably smaller when the period is larger than 0.4s. Compared with the horizontal bedrock acceleration response spectrum predicted by the attenuation relationship for the eastern part of China, the observed response spectrum shape is similar with the predicted ones, while almost all the observed response spectrum values (except station 32YCT)are smaller than the predicted bedrock acceleration response spectrum. These phenomena suggest that this earthquake has a weak impact on the seismic fortification standards in this area. Using H/V single-station spectral ratio method, amplitude and site amplification effect of the two typical stations are calculated, and the results show the H/V values are obviously larger than that of ground microtremor. This suggests that the site of the station has obvious amplification effect on ground motion.     

近断层强地震动场预测

以1997年4月11日新疆伽师地震（M_w6.1）为例,详细介绍了近断层强地震动场的预测方法.首先,用有限断层震源建模方法建立了该次地震的震源模型;然后,基于动力学拐角频率的地震动随机模拟方法,模拟了该次地震仅有主震加速度记录、且位于巨厚土层上的三个台站的加速度时程,并用实际地震记录进行了验证.在此基础上,基于预测的近断层77个节点的加速度时程的峰值绘制了该次地震的加速度场.结果表明,上述方法模拟的加速度时程在0.5 Hz以上的高频段是可行的、实用的;预测的近断层加速度场具有非常明显的上盘效应.地表最大加速度的范围与断层面上最大凹凸体位置相对应,说明与断层面上凹凸体相对应的地面上的建（构）筑物将会遭受到较为严重的震害.     

Deterministic seismic scenarios for North East India

In this paper, ground motion during six past devastating earthquakes and one possible future event in the northeastern part of India is estimated by seismological approaches. Considering uncertainty in the input source parameters, a series of ground motions have been simulated. The peak ground acceleration (PGA) and response spectra at important cities and towns in the epicentral regions of these events are obtained. The PGA distribution over the entire northeastern region of India, encompassing the epicenter, is presented in the form of contours. The obtained results can be used for the seismic analysis and design of structures in this region.