渤海海洋石油平台设定地震反应谱的确定

以渤海海域内已兴建的BZ28-2石油平台为研究对象,综合确定性和概率地震危险性分析方法的优点,通过对渤海海域内地震活动时空分布特征、地震地质背景、发震断裂及其活动性、平台遭受破坏性地震震级与距离的可能组合、设定地震的实际发生概率等几个方面的研究,综合确定了平台不同超越慨率对应的设定地震参数,并基于以上研究结果,给出了B...     

浅壳与上地幔地震的水平加速度谱阻尼修正系数模型

对日本K-net和KiK-net台网中6 466条浅壳与上地幔地震动记录进行了统计分析,考虑四种场地类别分别建立了浅壳与上地幔地震的加速度谱阻尼修正系数模型,并利用随机效应模型将模型总残差分离为事件间残差、事件内残差（分为场地间残差和场地内残差）,计算其相应的标准差,探究地震震源、路径、场地等因素对模型误差的影响。研究结果显示:所提出的模型能较好地拟合实际计算值,其随机误差整体随谱周期和阻尼比的增大而增大;震源效应导致的随机误差在谱周期小于2.0 s时小于其它效应;在大部分谱周期上,场地效应导致的随机误差小于路径效应及其它效应;事件间残差与震源和震源深度显著相关,场地内残差与震源距显著相关。      

浅壳与上地幔地震竖向加速度谱阻尼修正系数模型

本文基于日本KiK-Net,K-Net台网及汶川地震中6 000余条浅壳与上地幔地震竖向加速度记录,分场地类型建立了包含阻尼比和谱周期两个参数的阻尼修正系数模型,用以调整无震级和震源距信息的设计谱。基于固定效应模型对阻尼修正系数对数值及阻尼比对数值的三次多项式进行线性回归得到模型表达式,基于随机效应模型对阻尼修正系数模型的残差及残差的标准差进行分离,分析震源、路径以及场地效应对模型误差的影响。研究结果表明:高阻尼长周期震源效应引起的残差大于其他效应引起的残差;场地效应引起的残差小于其他效应引起的残差。对模型残差的标准差及阻尼比对数值进行线性回归,回归方程易于计算模型残差的标准差。     

从反应谱求功率谱的精确方法及其应用

本文对由反应谱求功率谱的近似公式的误差进行了讨论,从而说明了精确求解地震动功率谱的必要性,并从构造函数的特征出发,提出了一类符合要求的构造函数族,同时对其参数的取值加以讨论。最后给出了一个算例,展示了从反应谱求功率谱的精确方法与近似方法在数值上的差别,以及对人造地震动的影响。     

A ground motion selection and modification method capturing response spectrum characteristics and variability of scenario earthquakes

Earthquake ground motion variability is one of the primary sources of uncertainty in the assessment of the seismic performance of civil systems. The paper presents a novel method to select and modify ground motions to achieve specified response spectrum variability. The resulted ground motions capture the median, standard deviation and correlations of response spectra of an earthquake scenario conditioned on a specified earthquake magnitude, source-to-site distance, fault mechanism, site condition, etc.     

川滇甘陕地区地震的加速度峰值比和竖向反应谱的统计分析

本文以国内川滇甘陕地区263个有详细场地资料的强震台站获得的802组地震动加速度记录为基础,研究了该地区加速度峰值比的总体分布特征,分别探讨了震中距和震级对加速度峰值比的影响特征,按照水平反应谱的标定方法对竖向反应谱进行标定并对其进行了统计分析。统计分析结果显示:竖向与水平向加速度峰值比的概率分布总体服从极值Ⅱ型分布,加速度峰值比均值为0.6,加速度峰值比≤0.65的累积频率为64%;Ⅱ类场地的加速度峰值比随震中距增大而减小;大震近场的加速度峰值比基本上远高于0.65;最后本文给出了不同场地类别下竖向反应谱特征参数,并与水平向反应谱特征参数进行了比较。     

Stochastic modeling of Iranian earthquakes and estimation of ground motion for future earthquakes in Greater Tehran

Strong-motion data from eight significant well-documented earthquakes in Iran have been simulated using a stochastic modeling technique for finite faults proposed by Beresnev and Atkinson [Bull Seismol Soc Am 87 (1997) 67–84; Seism Res Lett 69 (1998) 27–32]. The database consists of 61 three-component records from eight earthquakes of magnitude ranging from M 6.3 to M 7.4, recorded at hypocentral distances up to 200 km. The model predictions are in good agreement with available Iranian strong-motion data as evidenced by near-zero average of differences between logarithms of the observed and predicted values for all frequencies. The strength factor, sfact, a quantity that controls the high-frequency radiation from the source is determined, on an event-by-event basis, by fitting simulated to observed response spectra.     

东北地区地震活动的Rydelek-Sacks周期性检验和震级-周期谱研究

为检验中国东北地区地震活动可能存在的周期性特征和深、浅源地震在周期性活动上的相关性,利用Rydelek-Sacks检验方法和不同的地震目录,考虑了地震震级的选取对周期性特征识别可能存在的影响,并在震级-周期谱中进行了比较研究.对该地区1970-2009年ML≥4.5浅源地震、1920-2009年Ms≥5.0浅源地震和1...     

地震与爆破的波谱差异

在对中国数字地震台网（ＣＤＳＮ）兰州台近年来记录到的兰州附近的５个工业爆破和发生在同一地区震级相近的７个天然地震作波谱分析和比较后,发现人工爆破和天然地震的波谱参数与震源参数有较大的差异,在震级与震源深度相近的条件下,主要差异有：①爆破的Ωｍ（ω）值明显大于地震的Ωｍ（ω）值,Ωｍ（ω）爆≈１．５Ωｍ（ω）震;②爆破的Ω（０）值明显大于地震的Ω（０）值,Ω（０）爆≈１．９Ω（０）震;③爆破的震源线     

Protracted river response to medieval earthquakes

Mountain rivers respond to strong earthquakes by rapidly aggrading to accommodate excess sediment delivered by co-seismic landslides. Detailed sediment budgets indicate that rivers need several years to decades to recover from seismic disturbances, depending on how recovery is defined. We examine three principal proxies of river recovery after earthquake-induced sediment pulses around Pokhara, Nepal's second largest city. Freshly exhumed cohorts of floodplain trees in growth position indicate rapid and pulsed sedimentation that formed a fan covering 150 km² in a Lesser Himalayan basin with tens of metres of debris between the 11th and 15th centuries AD. Radiocarbon dates of buried trees are consistent with those of nearby valley deposits linked to major medieval earthquakes, such that we can estimate average rates of re-incision since. We combine high-resolution digital elevation data, geodetic field surveys, aerial photos, and dated tree trunks to reconstruct geomorphic marker surfaces. The volumes of sediment relative to these surfaces require average net sediment yields of up to 4200 t km^–2 yr^–1 for the 650 years since the last inferred earthquake-triggered sediment pulse. The lithological composition of channel bedload differs from that of local bedrock, confirming that rivers are still mostly evacuating medieval valley fills, locally incising at rates of up to 0.2 m yr^–1. Pronounced knickpoints and epigenetic gorges at tributary junctions further illustrate the protracted fluvial response; only the distal portions of the earthquake-derived sediment wedges have been cut to near their base. Our results challenge the notion that mountain rivers recover speedily from earthquakes within years to decades. The valley fills around Pokhara show that even highly erosive Himalayan rivers may need more than several centuries to adjust to catastrophic perturbations. Our results motivate some rethinking of post-seismic hazard appraisals and infrastructural planning in active mountain regions. © 2018 John Wiley & Sons, Ltd.     

Rocking response of rigid blocks to earthquakes

This investigation deals with the rocking response of rigid blocks subjected to earthquake ground motion. A numerical procedure and computer program are developed to solve the non-linear equations of motion governing the rocking motion of rigid blocks on a rigid base subjected to horizontal and vertical ground motion. The response results presented show that the response of the block is very sensitive to small changes in its size and slenderness ratio and to the details of ground motion. Systematic trends are not apparent: The stability of a block subjected to a particular ground motion does not necessarily increase monotonically with increasing size or decreasing slenderness ratio. Overturning of a block by a ground motion of particular intensity does not imply that the block will necessarily overturn under the action of more intense ground motion. In contrast, systematic trends are observed when the problem is studied from a probabilistic point of view with the ground motion modelled as a random process. The probability of a block exceeding any response level, as well as the probability that a block overturns, increases with increase in ground motion intensity, increase in slenderness ratio of the block and decrease in its size. It is concluded that probabilistic estimates of the intensity of ground shaking may be obtained from its observed effects on monuments, minarets, tombstones and other similar objects provided suitable data in sufficient quantity is available, and the estimates are based on probabilistic analyses of the rocking response of rigid blocks, considering their non-linear dynamic behaviour.     

Stochastic response of rigid foundations

While the study of kinematic interaction (i.e. the dynamic response of massless foundations to seismic loads) calls, in general, for advanced analytical and numerical techniques, an excellent approximation was proposed recently by Iguchi.^1,2 This approximation was used by the authors to analyse embedded foundations subjected to spatially random SH-wave fields, i.e. motions that exhibit some degree of incoherence. The wave fields considered ranged from perfectly coherent motions (resulting from seismic waves arriving from a single direction) to chaotic motions, resulting from waves arriving simultaneously from all directions. Additional parameters considered were the shape of the foundation (cylindrical or rectangular) and the degree of embedment. It was found that kinematic interaction usually reduces the severity of the motions transmitted to the structure, and that incoherent motions do not exhibit the frequency selectivity (i.e. narrow valleys in the foundation response spectra) that coherent motions do.     

Biot response spectrum

The response spectrum method (RSM) in earthquake engineering was conceived and then fully developed by M.A. Biot (1905–1985) during the period of about 10 yr, between 1932 and 1942. On the occasion of the 100th anniversary of Biot's birth, this paper reviews his contributions to earthquake engineering, and then briefly outlines the milestones in the later evolution of the RSM, and the eventual introduction and acceptance of the method by the engineering disciplines in the early 1970s. The role of the Biot spectrum in the formulation of design codes is illustrated briefly, using examples from code development in California. Finally, the limitations of the linear response superposition method are discussed, and future directions for the development of earthquake-resistant design tools are suggested.     

Stochastic ground-motion simulation of two Himalayan earthquakes: seismic hazard assessment perspective

The earthquakes in Uttarkashi (October 20, 1991, M _w 6.8) and Chamoli (March 8, 1999, M _w 6.4) are among the recent well-documented earthquakes that occurred in the Garhwal region of India and that caused extensive damage as well as loss of life. Using strong-motion data of these two earthquakes, we estimate their source, path, and site parameters. The quality factor (Q _β ) as a function of frequency is derived as Q _β (f) = 140f ^1.018. The site amplification functions are evaluated using the horizontal-to-vertical spectral ratio technique. The ground motions of the Uttarkashi and Chamoli earthquakes are simulated using the stochastic method of Boore (Bull Seismol Soc Am 73:1865–1894, 1983). The estimated source, path, and site parameters are used as input for the simulation. The simulated time histories are generated for a few stations and compared with the observed data. The simulated response spectra at 5% damping are in fair agreement with the observed response spectra for most of the stations over a wide range of frequencies. Residual trends closely match the observed and simulated response spectra. The synthetic data are in rough agreement with the ground-motion attenuation equation available for the Himalayas (Sharma, Bull Seismol Soc Am 98:1063–1069, 1998).     

Study of the anomaly of seismic fractal spectrum before strong earthquakes

3 Conclusions The research of some theoretical Contor models of multi-scale and the numerical model of seismic spatial distribution show that the physical property of anomalies in seismic fractal spectrums is due to an increment of nonuniformity in the point set (earthquakes), in another word, the complexity increases. It is exactly the general precursory that the distribution pattern becomes complex from simple or nonuiform from uniform. So seismic multi-fractal spectrums is one of the best methods or tools for describing the complexity of seismic temporal-spatial distribution patterns. According to this view of point, taking the anomalies of the seismic multi-fractal spectrum as the earthquake prediction criterion is very valuable and worth while further studying. This project is supported by Chinese Joint Seismological Science Foundation.     

成层地基一维土层对地震的随机反应分析

首先基于改进的一维剪切梁模型，对成层土层推导了确定自振频率、振型函数、参与系数及稳态动力响应的封闭型解析表达式，首次证明了成层土层振型函数的正交性，然后在此基础上，利用随机振动理论，研究了成层土层对地震的随机动力反应问题，关于基岩输入地震加速度的功率谱密度函数，考虑了两种形式：白噪声谱和过滤白噪声谱。数值计算结果表明：对这两种谱，土层的最大期望反应是不相同的；平稳输入与输出过高估计了土层的随机反应。     

Stochastic response of multistorey yielding frames

A model for the random vibration of hysteretic and degrading plane frames to Gaussian shot noise or filtered shot noise is presented. The model, which combines the discrete hinge concept previously used in deterministic frame analysis with Bouc's smooth system hysteresis, results in a non-linear set of differential equations which can be linearized in closed form without recourse to the Krylov-Bogoliubov assumptions. Solution is iterative in the stationary case and by numerical integration with stepwise updates in the non-stationary case. Numerical studies are presented of strong girder and strong column two storey, one bay frames. These studies indicate that the model can locate the sites of yielding and provide reasonable values of structural response as compared with simulation data. Moreover, the model can provide a joint by joint breakdown of the structure energy dissipation rate.     

Consecutive combined response spectrum

Appropriate estimates of earthquake response spectrum are essential for design of new structures, or seismic safety evaluation of existing structures. This paper presents an alternative procedure to construct design spectrum from a combined normalized response spectrum(NRSC) which is obtained from pseudo-velocity spectrum with the ordinate scaled by different peak ground amplitudes(PGA, PGV, PGD) in different period regions. And a consecutive function f(T) used to normalize the ordinates is defined. Based on a comprehensive study of 220 strong ground motions recorded during recent eleven large worldwide earthquakes, the features of the NRSC are discussed and compared with the traditional normalized acceleration, velocity and displacement response spectra(NRSA, NRSV, NRSD). And the relationships between ground amplitudes are evaluated by using a weighted mean method instead of the arithmetic mean. Then the NRSC is used to define the design spectrum with given peak ground amplitudes. At last, the smooth spectrum is compared with those derived by the former approaches, and the accuracy of the proposed spectrum is tested through an analysis of the dispersion of ground motion response spectra.     

Characteristics of strong ground motion for typical Australian intra-plate earthquakes and their relationship with the recommended response spectra

Global epicentre maps show that the majority of earthquakes are inter-plate, although moderate to large earthquakes do occur intra-plate, i.e. within the plates. The seismicity of the Australian continent is typical of intra-plate environments and a magnitude M_L 6 earthquake has an average return period of about 5 years. Recordings of Australian intra-plate earthquakes are investigated here to characterise their frequency content, peak acceleration and duration.Due to lack of quality strong motion records of large intra-plate earthquakes at short distances, synthetic seismograms are commonly used for testing structural behaviour. An empirical Green's Function method (Geophys. Res. Lett., 5 (1978), 1–4; Proceedings of the Third International Microzonation Conference, Seattle, USA, vol. 1, (1982), pp. 447–458.) is chosen to simulate a large earthquake by summation in time of a number of smaller earthquakes or sub-events, each given a slightly different origin time to represent more realistically the propagation of a rupture along an assumed fault plane. In the first instance, recordings on rock of the magnitude M_L 2.3 aftershock of the 29 December 1989 Newcastle earthquake were used as sub-events to simulate the main shock of magnitude M_L 5.6. Validation studies for events recorded elsewhere in Australia are also considered.The response spectra of such synthetic events will be compared with the recommended spectra developed empirically from a statistical analysis of strong motion data for magnitude 5.4–6.5 intra-plate earthquakes recorded in other parts of the world and normalised to a peak ground velocity of 50 mm/s which is typical for a return period of 500 years in Australia (Australasian Structural Engineering Conference, Auckland, New Zealand, (1998), pp. 439–444.). Preliminary results from this comparison with the response spectra recommended for the Building Code of Australia show that the synthetic waveforms produced by this method are realistic and can be used to represent ground motion during typical Australian intra-plate earthquakes.     

地磁加卸载响应比与地震对应关系研究

通过对浙、沪、苏邻近 4个地磁观测点的近十年的资料,及邻近区域10个地震进行了每日Z分量日变幅加卸载响应比随时间变化和响应比月均值的相关研究。结果表明:加卸载响应比阈值P₀(Z) 和响应比月均值P_M(Z)的大小与地震的震级、震中距及异常出现的早晚并非完全呈线性相关;当响应比值大于某一阈值时,有可能发生一定震级的地震 ;按该方法结果综合分析,截止1998年9月底,未来1年左右的时间内在该研究区域或更大范围(含台湾区域)有可能发生6级左右的地震。该方法可作为分析预报手段参与中短期和短临地震趋势判断的一种新方法。