大连开发区场地地震设计参数

根据工作区潜在震源区划分、潜在震源区地震活动性参数和地震动衰减关系, 进行场地地震危险性分析, 得到不同概率水平下场区相应地震烈度和基岩水平加速度峰值及其反应谱。根据场地工程地震条件划分不同地质单元及相应的场地类别, 进行不同概率水平的地震反应分析计算, 确定地震动设计参数。     

基于原地应力实测数据探讨华北典型强震区断裂活动危险性及其对雄安新区的影响

华北地区距雄安新区300 km范围内包括唐山、邢台和张北三个典型强震区,近50年来,先后发生1966年邢台7.2级、1976年唐山7.8级和1998年张北6.2级强震活动,未来仍具发生破坏性地震的风险。在现今构造应力环境下,3个典型强震区内断裂活动危险性如何、再次发生中强地震对雄安新区地面稳定性有怎样的影响,这些都是要回答的问题。对此,本文首先基于唐山、邢台和张北强震区关键构造部位深孔水压致裂地应力测量数据,依据Byerlee断层滑动失稳摩擦准则,计算各强震区内潜在发震断层的临界失稳状态,探讨断裂活动危险性;之后依据中华人民共和国第五代《中国地震动参数区划图》之《中国大陆及邻区潜在震源区划分图》,厘定雄安新区外围300 km范围内主要潜在震源区和震级上限;最后选取适宜的地震烈度衰减模型,定量计算主要潜在震源区未来发生震级上限地震时对雄安新区地震烈度的影响,进而为雄安新区及重大工程抗震设防提供科学参考。结果表明：(1)唐山、邢台和张北强震区内主要潜在震源区未来发生震级上限地震产生的地震烈度衰减至雄安新区时均位于Ⅳ~Ⅶ度;(2)北京通州及邻区发生8.0级地震、涞水—高碑店沿线发生6.5级地震会在雄安新区产生Ⅶ度地震烈度,震害较轻;(3)其他潜在震源区在雄安新区产生的地震烈度均小于V度,并不会产生显著震害效应。鉴于此,雄安新区抗震设防烈度建议由原Ⅶ度调至Ⅷ度为宜。     

沙牌坝址基岩场地地震动输入参数研究

重大水利水电工程地震动输入参数必须根据专门的地震危险性分析结果来确定。目前由地震危险性分析得到的一致概率反应谱具有包络的意义,不能反映实际地震的频谱特性,输入“一致概率反应谱”可能导致地震作用偏大;拟合设计反应谱人工生成地震动加速度时程的频率非平稳性也没有得到很好解决。为了解决这些问题,得到与坝址地震危险性一致、具体地震的输入参数,结合沙牌大坝提出了一套适用于重大水利水电工程基岩场地地震动输入参数确定方法：通过以有效峰值加速度为参数的概率地震危险性计算分析,确定坝址不同超越概率下的有效峰值加速度及对坝址贡献最大的潜在震源区;在最大贡献潜在震源内利用震级空间联合分布概率最大法确定坝址设定地震,依据加速度反应谱衰减关系确定与坝址设定地震对应的设计反应谱;根据设定地震结果和时变功率谱模型参数衰减关系确定时变功率谱,将时变功率谱和最小相位谱按三角级数叠加法进行强度和频率非平稳地震加速度时程合成。在对沙牌坝址区域的地震活动性及地震构造环境分析评价的基础上,采用上述方法,得到了坝址基岩场地不同超越概率下的有效峰值加速度、设计反应谱、强度和频率非平稳地震加速度时程等地震动输入参数。     

鄂西清江两水利枢纽坝址区地震危险性对比分析

本文在研究清江流域及外围区域地震地质条件和地震分布规律的基础上，划分了１、２个潜在震源区，并确定其相应的地震活动性参数，同时探讨区域地震烈度衰减规律及各潜在震源区对隔河岩和水布垭两坝址的影响烈度、进而复泊松模型，评价两坝址的地震危险性，获得了丙坝址不同期限内的地面峰值加速度及其相应的超越概率。根据对比分析，水布垭坝址的地震危险性比隔洒岩坝址小。     

上海市南部地区地震危险性分析

本文通过对工作区内地震地质、地球物理场特征研究,确定了场区周围九个潜在震源区,分析计算得出各潜在震源区的地震活动性参数。用概率论的方法,以洪华生等人提出的《断层—破裂模型》计算得到上海市南部地区地震烈度年超越概率以及10、20、50、100、200、300、500年内场区的地震影响烈度超越概率,并对这一地区的地震危险性进行了估计。     

近断层强地震动预测中的有限断层震源模型

提出了近断层强地震动预测中建立活断层上设定地震有限断层震源模型的方法和步骤.首先,根据地震地质和地震活动性调查以及地球物理勘探等资料,确定活断层的空间方位和滑动类型; 然后,根据地震定标律确定活断层的宏观震源参数; 第三,将高强体模型与k平方滑动模型相结合,产生断层破裂面上的混合滑动分布.在此基础上,预测了与1994年Northridge地震断层类型、矩震级(M_w6.7)基本一致的设定地震的有限断层震源模型.最后,将预测的有限断层震源模型与基于地震学的、使用动力学拐角频率的地震动随机合成方法相结合,预测了1994年Northridge地震近断层12个基岩台站的加速度时程,并和实际记录进行了对比.结果表明,用上述方法和步骤建立的有限断层震源模型是可行、实用的.      

近源地震动峰值加速度衰减关系影响因素分析

本文收集了丰富的强震资料, 以峰值加速度为例, 采用简单且体现近场峰值加速度PGA震级饱和和距离饱和特性的衰减模型, 研究了表征震级与距离饱和效应的R0(M)的性质。R0与震级相关, 同时与震源性质、地震波频谱有关。在单个地震的R0(M)的求取中, 由于R0与系数d几乎呈线性关系, 所以要求单个地震R0的值, 必须先根据理论约束确定d的大小。在检验衰减方程的预测效果时, 不仅要判断衰减曲线是否反映了实测资料的平均变化趋势, 而且要判断实测资料是否绝大多数落在84%及16%概率水平的预测曲线之内(之间).     

苏州第四纪深厚沉积层一维等效线性和非线性地震反应对比分析

合理描述土体动力本构关系对场地设计地震动参数取值的准确性有显著影响。以苏州城区200 m深的钻孔剖面为研究对象,对比分析了一维等效线性波传分析法（ELA法）和基于修正Matasovic本构模型的多自由度集中质量非线性分析法（NLA法）给出的深厚场地地震反应,研究了基岩输入地震动特性和地震基岩面的选取对深厚场地地震反应的影响。结果表明：（1）随基岩地震动强度（PGA）的增大,ELA法给出的地表PGA呈单调递增的特征,而NLA法给出的地表PGA呈先快速增大后缓慢减小或几乎不变的趋势;（2）ELA法和NLA法给出的地表加速度反应谱（Sa谱）在短周期范围内存在明显差异,ELA法对基岩高频地震动具有显著的滤波效应,而NLA法对基岩高频地震动的影响表现为随基岩PGA的增大先放大后减小的特征;（3）随地震基岩面深度的增大,地表Sa谱的谱值呈现出稍许增大的趋势,但对周期T<0.1 s部分,NLA法给出的地表Sa谱的谱值则呈现出稍许减小的现象;（4）中、大震作用下,地表地震动持时不仅与基岩地震动特性有关,还与地震反应分析方法和地震基岩面的选取密切相关,NLA法能更合理地反映基岩地震动强度和上覆土层厚度对地表地震动持时的影响。     

宁波地区地震危险性分析简述

本文论述了宁波盆地附近区域构造的活动性及其对宁波地区地震的影响，并通过对该区历史地震的时空分析划分了潜在震源区，确定了地震活动参数。采用地震点源扩散模型计算了宁波市的地震危险性，得到了地震烈度和峰值加速度的超越概率。从而由地质构造活动性和地震活动性两方面评估了宁波地区的地震危险性。可作为各类工程建设规划参考。     

走滑断层地震地表断裂位错估计方法研究

为对一次地震中可能造成的地表断裂位错作出较准确的估计,采用拟静力弹塑性有限元方法,分别对覆盖土层为粉质黏土和黏土情况下,走滑断层引发的地震地表断裂进行了数值模拟分析。根据历史震害数据回归拟合的震级M与基岩位错 的关系式以及数值计算结果,建立了震级M与地表位错 的关系式。公式中考虑了土层厚度H对地表位错 的影响,而不仅仅局限于根据震级M的大小通过统计公式来估算地表断裂位错 。结果表明,走滑断层引发的地震地表断裂位错不仅与震级的大小有关,还与土层厚度和土层性质有关;在相同震级作用下,随着土层厚度的增加,地表位错逐渐减小;在相同震级和相同土层厚度下,上覆土层为粉质黏土时产生的地表位错要大于上覆土层为黏土时产生的地表位错;根据拟合的公式估计出不同震级情况下可不考虑走滑断层影响的临界覆盖土层厚度值,有助于提高活动断裂地震危险性评估工作的可靠性。     

Seismicity, seismotectonics and seismic hazard of Italy

A first generation of probabilistic seismic hazard maps of the Italian country are presented. They are based on seismogenic zoning deriving from a kinematic model of the structural tectonic units and on an earthquake catalogue with the foreshock and aftershock events filtered out. The following ground motion parameters have been investigated and mapped using attenuation equations based on strong-motion recordings of Italian earthquakes: peak ground acceleration and velocity; Arias intensity; strong motion duration; and the pseudovelocity and pseudoacceleration spectral values at 14 fixed frequencies both for the vertical and the largest horizontal component. A Poissonian model of earthquake occurrence is assumed as a default and the hazard maps are presented in terms of ground motion values expected to be exceeded at a 10% probability level in 50 years (return period 475 years) according to the requirement of Eurocode 8 for the seismic classification of national territories, as well as in terms of exceedance probabilities of selected ground motion values. Finally, as a tentative study, the use of hybrid methods (implementing both seismogenic zones and structures), renewal processes (including earthquake forecasting) and the influence of site effects (as the basis for the planning of earthquake scenarios) were explored.     

Generation of stochastic earthquake ground motion in western Saudi Arabia as a first step in development of regional ground motion prediction model

Earthquake ground motion model is an essential part of seismic hazard assessment. The model consists in several empirical ground motion prediction equations (GMPEs) that are considered to be applicable to the given region. When the recorded ground motion data are scarce, numerical modeling of ground motion based on available seismological information is widely used. We describe results of stochastic simulation of ground motion acceleration records for western Saudi Arabia. The simulation was performed using the finite fault model and considering peak ground acceleration and amplitudes of spectral acceleration at natural frequencies 0.2 and 1.0 s. Based on the parameters of the input seismological model that were accepted in similar previous studies, we analyze influence of variations in the source factor (stress drop) and in the local attenuation and amplification factors (kappa value, crustal amplification). These characteristics of the model are considered as the major contributors to the ground motion variability. The results of our work show that distribution of simulated ground motion parameters versus magnitude and distance reveals an agreement with the GMPEs recently used in seismic hazard assessment for the region. Collection of credible information about seismic source, propagation path, and site attenuation parameters using the regional ground motion database would allow constraining the seismological model and developing regional GMPEs. The stochastic simulation based on regional seismological model may be applied for generation of ground motion time histories used for development of analytical fragility curves for typical constructions in the region.     

Perceptible earthquakes in the broad Aegean area

A probabilistic estimate of seismic hazard can be obtained from the spatial distribution, of earthquake sources, their frequency–magnitude distribution and the rate of attenuation of strong ground motion with distance. We calculate the earthquake perceptibility, i.e. the annual probability that a particular level of ground shaking will be generated by earthquakes of particular magnitude, by weighting frequency–magnitude data with the predicted felt area for a given level of ground shaking at a particular magnitude. This provides an earthquake selection criterion that can be used in the anti-seismic design of non-critical structures. We calculate the perceptibility, at a particular value of isoseismal intensity, peak ground acceleration and velocity, as a function of source magnitude and frequency for the broad Aegean area using local attenuation laws. We use frequency–magnitude distributions that were previously obtained by combining short-term catalogue data with tectonic moment rate data for 14 tectonic zones in Greece with sufficient earthquake data, and where contemporary strain rates are available from satellite data. Many of the zones show a ‘characteristic earthquake’ distribution with the most perceptible earthquake equal to the maximum magnitude earthquake, but a relatively flat perceptibility between magnitudes 6 and 7. The maximum perceptible magnitude is in the fastest-deforming region in the middle of the Aegean sea, and tends to be systematically low on the west in comparison to the east of the Aegean sea. The tectonic data strongly constrain the long-term recurrence rates and lead to low error estimates (±0.2) in the most perceptible magnitudes.     

Probabilistic seismic hazard analysis for Sumatra, Indonesia and across the Southern Malaysian Peninsula

The ground motion hazard for Sumatra and the Malaysian peninsula is calculated in a probabilistic framework, using procedures developed for the US National Seismic Hazard Maps. We constructed regional earthquake source models and used standard published and modified attenuation equations to calculate peak ground acceleration at 2% and 10% probability of exceedance in 50 years for rock site conditions. We developed or modified earthquake catalogs and declustered these catalogs to include only independent earthquakes. The resulting catalogs were used to define four source zones that characterize earthquakes in four tectonic environments: subduction zone interface earthquakes, subduction zone deep intraslab earthquakes, strike-slip transform earthquakes, and intraplate earthquakes. The recurrence rates and sizes of historical earthquakes on known faults and across zones were also determined from this modified catalog. In addition to the source zones, our seismic source model considers two major faults that are known historically to generate large earthquakes: the Sumatran subduction zone and the Sumatran transform fault. Several published studies were used to describe earthquakes along these faults during historical and pre-historical time, as well as to identify segmentation models of faults. Peak horizontal ground accelerations were calculated using ground motion prediction relations that were developed from seismic data obtained from the crustal interplate environment, crustal intraplate environment, along the subduction zone interface, and from deep intraslab earthquakes. Most of these relations, however, have not been developed for large distances that are needed for calculating the hazard across the Malaysian peninsula, and none were developed for earthquake ground motions generated in an interplate tectonic environment that are propagated into an intraplate tectonic environment. For the interplate and intraplate crustal earthquakes, we have applied ground-motion prediction relations that are consistent with California (interplate) and India (intraplate) strong motion data that we collected for distances beyond 200 km. For the subduction zone equations, we recognized that the published relationships at large distances were not consistent with global earthquake data that we collected and modified the relations to be compatible with the global subduction zone ground motions. In this analysis, we have used alternative source and attenuation models and weighted them to account for our uncertainty in which model is most appropriate for Sumatra or for the Malaysian peninsula. The resulting peak horizontal ground accelerations for 2% probability of exceedance in 50 years range from over 100% g to about 10% g across Sumatra and generally less than 20% g across most of the Malaysian peninsula. The ground motions at 10% probability of exceedance in 50 years are typically about 60% of the ground motions derived for a hazard level at 2% probability of exceedance in 50 years. The largest contributors to hazard are from the Sumatran faults.     

Tectonic stress,seismicity, and seismic hazard in the southeastern Carpathians

Intermediate-depth earthquakes in the Vrancea region occur in response to stress generation due to descending lithosphere beneath the southeastern Carpathians. In this article, tectonic stress and seismicity are analyzed in the region on the basis of a vast body of observations. We show a correlation between the location of intermediate-depth earthquakes and the predicted localization of maximum shear stress in the lithosphere. A probabilistic seismic hazard assessment (PSHA) for the region is presented in terms of various ground motion parameters on the utilization of Fourier amplitude spectra used in engineering practice and risk assessment (peak ground acceleration, response spectra amplitude, and seismic intensity). We review the PSHA carried out in the region, and present new PSHA results for the eastern and southern parts of Romania. Our seismic hazard assessment is based on the information about the features of earthquake ground motion excitation, seismic wave propagation (attenuation), and site effect in the region. Spectral models and characteristics of site-response on earthquake ground motions are obtained from the regional ground motion data including several hundred records of small and large earthquakes. Results of the probabilistic seismic hazard assessment are consistent with the features of observed earthquake effects in the southeastern Carpathians and show that geological factors play an important part in the distribution of the earthquake ground motion parameters.     

Modeling of seismic hazard for Turkey using the recent neotectonic data

Recent developments in the neotectonic framework of Turkey introduced new tectonic elements necessitating the reconstruction of Turkey's seismic hazard map. In this regard, 14 seismic source zones were delineated. Maximum earthquake magnitudes for each seismic zones were determined using the fault rupture length approximation. Regression coefficients of the earthquake magnitude–frequency relationships for the seismic zones were compiled mostly from earlier works. Along with these data, a strong ground motion attenuation relationship developed by Joyner and Boore [Joyner, W.B., Boore, D.M., 1988. Measurement, characterization, and prediction of strong ground motion. Earthquake Engineering and Soil Dynamics, 2. Recent Advances Ground Motion Evaluation, pp. 43–102.] was utilized to model the seismic hazard for Turkey using the probabilistic approach. For the modeling, the “earthquake location uncertainty” concept was employed. A grid of 5106 points with 0.2° intervals was constituted for the area encompassed by the 25–46°E longitudes and 35–43°N latitudes. For the return periods of 100 and 475 years, the peak horizontal ground acceleration (pga) in bedrock was computed for each grid point. Isoacceleration maps for the return periods of 100 and 475 years were constructed by contouring the pga values at each node.     

关于工程地震实践若干问题

本文介绍和讨论了有关工程地震实践中的某些成果和问题:(1)考虑近源地震动饱和的衰减场模式及其转换;(2)核电厂厂址设计基准地面运动和不同核法规对人工设计时程合成的技术要求对比;(3)水利水电工程场地地震安全性评价;(4)以金沙江中下游地区为例介绍地震设防区划和设防区划图系;(5)从科学性和工程可接受性, 以工程法规为基础提出工程活动断裂的定义、断裂活动性工程分类和地震断错形变工程评价。     

Sensitivity analysis of seismic hazard for the northwestern portion of the state of Gujarat, India

We test the sensitivity of seismic hazard to three fault source models for the northwestern portion of Gujarat, India. The models incorporate different characteristic earthquake magnitudes on three faults with individual recurrence intervals of either 800 or 1600 years. These recurrence intervals imply that large earthquakes occur on one of these faults every 266–533 years, similar to the rate of historic large earthquakes in this region during the past two centuries and for earthquakes in intraplate environments like the New Madrid region in the central United States. If one assumes a recurrence interval of 800 years for large earthquakes on each of three local faults, the peak ground accelerations (PGA; horizontal) and 1-Hz spectral acceleration ground motions (5% damping) are greater than 1 g over a broad region for a 2% probability of exceedance in 50 years' hazard level. These probabilistic PGAs at this hazard level are similar to median deterministic ground motions. The PGAs for 10% in 50 years' hazard level are considerably lower, generally ranging between 0.2 g and 0.7 g across northwestern Gujarat. Ground motions calculated from our models that consider fault interevent times of 800 years are considerably higher than other published models even though they imply similar recurrence intervals. These higher ground motions are mainly caused by the application of intraplate attenuation relations, which account for less severe attenuation of seismic waves when compared to the crustal interplate relations used in these previous studies. For sites in Bhuj and Ahmedabad, magnitude (M) 7 3/4 earthquakes contribute most to the PGA and the 0.2- and 1-s spectral acceleration ground motion maps at the two considered hazard levels.