Detailed seismic zoning of the East Kazakhstan region in the Republic of Kazakhstan

Kazakhstan is currently drafting new construction regulations that comply with the major provisions of the Eurocodes.Such regulations are created on the basis of seismic zoning maps of various degrees of detail,developed by our Institute of Seismology using a new methodological approach for Kazakhstan.The article is about creating the first normative map of the Detailed Seismic Zoning on a probabilistic foundation for the Republic of Kazakhstan’s East Kazakhstan region.We carried out the probabilistic assessment of seismic hazard using a methodology consistent with the main provisions of Eurocode 8and updated compared with that used in developing maps of Kazakhstan’s General Seismic Zoning and seismic microzoning of Almaty.The most thorough and current data accessible for the area under consideration were combined with contemporary analytical techniques.Updates have been done to not only the databases being used but also the way seismic sources were shown,including active faults now.On a scale of 1:1000000,precise seismic zoning maps of the East Kazakhstan region were created for two probabilities of exceedance:10%and 2%in 50 years in terms of peak ground accelerations and macroseismic intensities.The obtained seismic hazard distribution is generally consistent with the General Seismic Zoning of Kazakhstan’s previous findings.However,because active faults were included and a thoroughly revised catalog was used,there are more pronounced zones of increased danger along the fault in the western part of the region.In the west of the territory,acceleration values also increased due to a more accurate consideration of seismotectonic conditions.Zoning maps are the basis for developing new state building regulations of the Republic of Kazakhstan.

Probabilistic seismic hazard assessment of Kazakhstan and Almaty city in peak ground accelerations

As for many post-soviet countries, Kazakhstan’s building code for seismic design was based on a deterministic approach. Recently, Kazakhstan seismologists are engaged to adapt the PSHA(probabilistic hazard assessment) procedure to the large amount of available geological, geophysical and tectonic Kazakh data and to meet standard requirements for the Eurocode 8. The new procedure has been used within National projects to develop the Probabilistic GSZ(General Seismic Zoning) maps of the Kazakhstan territory and the SMZ(Probabilistic Seismic Microzoning) maps of Almaty city. They agree with the seismic design principles of Eurocode 8 and are expressed in terms of not only seismic intensity,but also engineering parameters(peak ground acceleration PGA). The whole packet of maps has been developed by the Institute of Seismology, together with other Kazakhstan Institutions. Our group was responsible for making analysis in PGA. The GSZ maps and hazard assessment maps for SMZ in terms of PGA for return periods 475 and 2475 years are considered in the article.

On the realization of seismic microzonation of Almaty (Kazakhstan) in ground accelerations based on the “continual” approach

Seismic microzonation for Almaty city for the first time use probabilistic approach and hazard is expressed in terms of not only macroseismic intensity,but also Peak Ground Acceleration(PGA).To account for the effects of local soil conditions,the continual approach proposed by A.S.Aleshin[1,2]was used,in which soil coefficients are a function of the continuously changing seismic rigidity.Soil coefficients were calculated using the new data of geological and geophysical surveys and findings of previous geotechnical studies.The used approach made it possible to avoid using soil categories and a jump change in characteristics of soil conditions and seismic impact.The developed seismic microzonation maps are prepared for further introduction into the normative documents of the Republic of Kazakhstan.

A Bayesian Approach to Seismic Hazard Estmation: Maximum Values of Magnitudes and Peak Ground Accelerations

A rather simple straightforward procedure of estimating maximum values of the considered parameter (earthquake magnitude in a given region or seismic peak ground acceleration at the considered site) and quantiles of its probabilistic distribution in a future time interval of a given length is presented. To assess the peak ground acceleration using this method, the input information is the earthquake catalog and the regressive relation where the peak seismic acceleration at a given point bears the magnitude and epicentral distance of the site considered (seismic attenuation law). The method is based on the Bayesian approach, in which the influence of uncertainties of magnitudes and seismic acceleration values can be taken into account. The main assumptions for the method are the Poissonian character of the seismic event flow, a frequency-magnitude law of Gutenberg-Richter’s type with a cutoff maximum value for the estimated parameter, and an earthquake catalog that has a rather large number of events. The method has been applied to seismic hazard estimation in California, the Balkans, and Japan.

Amplification Effect of Peak Ground Motion Acceleration in ClassⅡ and Ⅲ Sites over Shandong Provincet

In this paper, the amplification factor (ks) of peek ground motion with different exceedance probability in class Ⅱ and Ⅲ sites over Shandong Province was estimated by analyzing the seismic response data of soil layers collected from 358 boreholes of classⅡ sites and 140 boreholes of class Ⅲ site. From the results, one can conclude that: (1) The scatter plot of ks generally obeys a normal distribution; (2) ks decreases with the increase of the strength of input ground motion, which is more apparent in Class Ⅲ site than in class Ⅱ site; (3) for classⅡ site, with the increase of depth of the bedrock interface where ground motion inputs, ks increases gradually until to a stable value when the depth reaches up to approximately 20 meters or larger. Yet, for class Ⅲ site, ks is insensitive to the depth; (4) the average of ks for classⅡ site is 1.47, slightly larger than that used in the Seismic Ground Motion Parameters Zonation Map of China (GB 18306-2001). Also, ks in classⅡ and Ⅲ sites at different levels of peak ground acceleration over Shandong Province is preliminarily discussed in the paper.

Observations on the application of artificial neural network to predicting ground motion measures

Application of the artificial neural network （ANN） to predict pseudospectral acceleration or peak ground acceleration is explored in the study. The training of ANN model is carried out using feed-forward backpropagation method and about 600 records from 39 California earthquakes. The statistics of the residuals or modeling error for the trained ANN-based models are almost the same as those for the parametric ground motion prediction equations, derived through regression analysis; the residual or modeling error can be modeled as a normal variate. The similarity and differences between the predictions by these two approaches are shown. The trained ANN-based models, however, are not robust because the models with almost identical mean square errors do not always lead to the same predictions. This undesirable behaviour for predicting the ground motion measures has not been shown or discussed in the literature; the presented results, at least, serve to raise questions and caution on this problem. A practical approach to ameliorate this problem, perhaps, is to consider several trained ANN models, and to take the average of the predicted values from the trained ANN models as the predicted ground motion measure.

Assessment of seismic hazard of roller compacted concrete dam site in Gilgit-Baltistan of northern Pakistan

The proposed site of the Diamer Bhasha Dam in northern Pakistan is situated in an active tectonic zone with intensive seismicity,which makes it necessary for seismic hazard analysis(SHA).Deterministic and probabilistic approaches have been used for SHA of the dam site.The Main Mantle Thrust(MMT),Main Karakaram Thrust(MKT),Raikot-Sassi Fault(RKSF)and Kohistan Fault(KF)have been considered as major seismic sources,all of which can create maximum ground shaking with maximum potential earthquake(MPE).Deterministically estimated MPE for magnitudes of 7.8,7.7,7.6,and 7.1 can be produced from MMT,MKT,RKSF and KF,respectively.The corresponding peak ground accelerations(PGA)of 0.07,0.11,0.13 and 0.05 g can also be generated from these earthquakes,respectively.The deterministic analysis predicts a so-called floating earthquake as a MPE of magnitude=7.1 as close as 10 km away from the site.The corresponding PGA was computed as 0.38 g for a maximum design earthquake at the project site.However,the probabilistic analysis revealed that the PGA with 50%probability of exceedance in 100 years is 0.18 g.Thus,this PGA value related to the operational basis earthquake(OBE)is suggested for the design of this project with shear wave velocity(V_(s30))equal to 760 m/s under dense soil and soft rock conditions.

Study of the attenuation relationship for the Wenchuan M_s 8.0 earthquake

Prediction of peak ground acceleration is an essential element in engineering seismology and it has received great attention in last few decades. In this paper, a comprehensive database of the strong-motion records of the 2008 great Wenchuan Ms 8.0 earthquake is analyzed to investigate the seismic attenuation relationship and the directivity effects. In contrast to most existing seismic attenuation models, the proposed model considers explicitly the directivity effect which has primary influence on the magnitude of ground motion. Bayesian model updating is used to obtain the model parameters and the associated uncertainty. Comparative study is performed with the well-known Boore-Joyner-Fumal empirical formula. Results show that consideration of the directivity effect is vital in modeling the seismic attenuation relationship.

Probabilistic seismic hazard assessment of Nepal using multiple seismic source models

The potential for devastating earthquakes in the Himalayan orogeny has long been recognized. The 2015 MW7.8 Gorkha, Nepal earthquake has heightened the likelihood that major earthquakes will occur along this orogenic belt in the future. Reliable seismic hazard assessment is a critical element in development of policy for seismic hazard mitigation and risk reduction. In this study, we conduct probabilistic seismic hazard assessment using three different seismogenic source models(smoothed gridded, linear, and areal sources)based on the complicated tectonics of the study area. Two sets of ground motion prediction equations are combined in a standard logic tree by taking into account the epistemic uncertainties in hazard estimation. Long-term slip rates and paleoseismic records are also incorporated in the linear source model. Peak ground acceleration and spectral acceleration at 0.2 s and 1.0 s for 2% and 10%probabilities of exceedance in 50 years are estimated. The resulting maps show significant spatial variation in seismic hazard levels. The region of the Lesser Himalaya is found to have high seismic hazard potential. Along the Main Himalayan Thrust from east to west beneath the Main Central Thrust, large earthquakes have occurred regularly in history; hazard values in this region are found to be higher than those shown on existing hazard maps. In essence, the combination of long span earthquake catalogs and multiple seismogenic source models gives improved seismic hazard constraints in Nepal.

Seismic hazard assessment of Western Coastal Province of Saudi Arabia:deterministic approach

Seismic hazard assessment is carried out by utilizing deterministic approach to evaluate the maximum expected earthquake ground motions along the Western Coastal Province of Saudi Arabia. The analysis is accomplished by incorporating seismotectonic source model, determination of earthquake magnitude （Mmax）, set of appropriate ground motion predictive equations （GMPE）, and logic tree sequence. The logic tree sequence is built up to assign weight to ground motion scaling relationships. Contour maps of ground acceleration are generated at different spectral periods. These maps show that the largest ground motion values are emerged in northern and southern regions of the western coastal province in Saudi Arabia in comparison with the central region.

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.

Integration of Geophysical and Geotechnical Soil Characteristics for Local Site Seismic Design in Georgia

Recently, number of new constructions and engineering projects increased in Georgia, especially in Tbilisi, the capital of Georgia. Because of significant seismic activity of Caucasus region, seismic hazard assessment is very important issue for seismic-designing of engineering projects. Due to modern building codes, complex study of the local area is crucial for proper design of any type of constructions. Among them, following studies should be performed: probabilistic seismic hazard assessment, geological, geotechnical, geophysical, etc. After that, all information should be merged to each other and taken into account while designing of the project. In this paper, location of one construction site was selected as an application of complex study in order to show how can be merged different studies to each other. At the beginning, geological survey (well drilling) and geotechnical studies including laboratory tests were performed. Then geophysical profiling and downhole tests in wells were done by obtaining direct and shear wave velocities including estimation of physical-mechanical parameters. Next, probabilistic seismic hazard assessment and site-depended seismic hazard assessment were performed based on all information obtained by different studies. As a result, influence of local soil amplification on seismic hazard assessment is shown for the study area.

含软弱夹层场地的一维等效线性化地震响应研究

为了探明软弱夹层对场地的地震动响应影响,明确软弱夹层对地震场地的影响方式,基于等效线性化方法构建一维场地模型,对场地进行不同幅值的基岩地震动输入的响应计算,得到了多种地震工况下场地的PGA和地震波傅里叶谱.分析了地震波频谱在场地自然频率附近波段的谱值比曲线变化和软弱夹层对不同频率波段的消减情况,并根据滞回理论探明了地表加速度减小的原因.研究结果表明:在受到地震作用时,场地中的软弱夹层的剪切模量减小并且阻尼比增大,使得软弱夹层出现大应变并消耗了高频段的地震能量,使得传输到地表的地震波PGA减小;且当基岩输入地震强度增大时,地表PGA放大系数曲线呈现出逐渐减小并趋于平稳的规律性.

基于Matlab的地震动参数综合确定

本文主要介绍了基于Matlab编写的用于确定场地地震动参数的程序,从输入、处理和输出3大框架模块,结合笔者理解与经验对设计地震参数的确定过程进行较为详细分析。程序使用1个Excel文件整体控制输入参数,综合考虑了峰值加速度、场地类别、设计地震分组、区划图调整系数等因素,简化繁杂的反应谱数据处理过程,使用了不同规范推荐的规准谱,实现了钻孔反应谱的自动标定、自动保存图件并导出地震动参数表格;程序可对不同设计基准期、不同超越概率水准的多个钻孔、多条土层反应谱数据一次性综合分析,在处理区域性地震安全性评价等多场点工程项目时十分高效。文中对地震安全性评价工作中的实例进行了应用分析,程序既可以处理基岩反应谱,也可以对钻孔反应谱进行整体分析或单独分析,得到较为合理的场地地震动参数,有助于场地地震影响评价工作的开展。

钢-混工字组合连续梁桥地震易损性及其影响参数分析

以一座3×40m钢-混工字组合连续梁桥为依托,通过SAP2000建立不同墩高、不同上部结构荷载及不同上部主梁截面等全桥非线性有限元模型。选取峰值地面加速度(PGA)作为地震动强度参数,以桥墩位移延性比为损伤指标确定了完全破坏、严重破坏、中等破坏、轻微破坏、基本完好等5种结构破坏状态,分析了不同PGA作用下的桥墩易损性。研究结果表明:对于钢-混工字组合连续梁桥,相同桥墩截面尺寸、同一峰值地面加速度(PGA)下,桥墩高度越高,各个破坏状态的超越概率越小,其破坏风险越小;在合理的上部结构设计前提下,增加上部结构荷载,会降低桥墩的抗震性能;相同的下部结构布置,上部主梁采用钢-混组合结构,其桥墩易损性破坏概率要比同跨径的钢筋混凝土T型梁桥小,抗震性能更优越。建议桥梁抗震设计时重点关注上述因素的影响。

全球地震危险性图与抗震设防烈度关系浅析

抗震设防烈度是建筑抗震设计的一项基本参数,许多国外工程建设项目由于所在国无可供执行或参照的抗震设计规范,使得项目前期的场地勘察与结构设计缺乏相应依据。文章介绍了全球地震模型开源平台发布的全球地震危险性图,通过分析其基准场地与国标场地类别的联系,探求全球地震危险性图地震动峰值加速度与抗震设防烈度的对应关系,为国内外工程建设项目的岩土工程勘察和抗震设计提供参考依据。

Seismic attenuation relationship with homogeneous and heterogeneous prediction-error variance models

Peak ground acceleration(PGA) estimation is an important task in earthquake engineering practice.One of the most well-known models is the Boore-Joyner-Fumal formula,which estimates the PGA using the moment magnitude,the site-to-fault distance and the site foundation properties.In the present study,the complexity for this formula and the homogeneity assumption for the prediction-error variance are investigated and an effi ciency-robustness balanced formula is proposed.For this purpose,a reduced-order Monte Carlo simulation algorithm for Bayesian model class selection is presented to obtain the most suitable predictive formula and prediction-error model for the seismic attenuation relationship.In this approach,each model class(a predictive formula with a prediction-error model) is evaluated according to its plausibility given the data.The one with the highest plausibility is robust since it possesses the optimal balance between the data fi tting capability and the sensitivity to noise.A database of strong ground motion records in the Tangshan region of China is obtained from the China Earthquake Data Center for the analysis.The optimal predictive formula is proposed based on this database.It is shown that the proposed formula with heterogeneous prediction-error variance is much simpler than the attenuation model suggested by Boore,Joyner and Fumal(1993).

Probabilistic seismic hazard analysis in Nepal

The seismic ground motion hazard for Nepal has been estimated using a probabilistic approach. A catalogue of earthquakes has been compiled for Nepal and the surrounding region （latitude 26% N and 31.7% N and longitude 79° E and 90° E） from 1255 to 2011. The distribution of catalogued earthquakes, together with available geological and tectonic information were used to delineate twenty-three seismic source seismic source information and probabilistic earthquake hazard prediction relationship, peak ground accelerations （PGAs） have zones in Nepal and the surrounding region. By using the parameters in conjunction with a selected ground motion been calculated at bedrock level with 63%, 10%, and 2% probability of exceedance in 50 years. The estimated PGA values are in the range of 0.07-0.16 g, 0.21 0.62 g, and 0.38-1.1 g for 63%, 10%, and 2% probability of exceedance in 50 years, respectively. The resulting ground motion maps show different characteristics of PGA distribution, i.e., high hazard in the far-western and eastern sections, and low hazard in southern Nepal. The quantified PGA values at bedrock level provide information for microzonation studies in different parts of the country.

强度包线参数不确定性对土层地震反应影响研究

基于地震动衰减模型获取的强度包线参数是人工合成地震动的必备参数之一,目前已有多种地震动衰减模型成果,各自得到的结果有一定差异性,这势必影响土层地震反应分析结果以及基于此结果确定出的设计地震动参数。为研究这一影响,设定不同的震级、震中距,利用各衰减模型分别计算强度包线参数,获取对应的各强度包线参数的分布范围,并均匀划分取值点,以典型的不同强度加速度反应谱作为目标谱,人工合成一系列地震动并作为输入,计算来源与实际工程中不同场地类别的代表性场地的土层地震反应。研究表明:单独改变三个包线参数的大小对同一场地的地表峰值加速度并没有明显影响;部分场地随着t1、ts、c的增长,在某些区间呈现相反的变化趋势;部分类别场地之间的地表峰值加速度在震中距与震级变化时差值大致固定。强度包线参数的不确定性对土层地震反应分析结果有重要影响,人工合成地震动时要慎重选取。

基于地震灾害风险普查的概率地震危险性分析--以从化区为例

为了厘定概率地震危险性分析方法在地震灾害风险调查与评估工作中的适用性,针对从化区,以中国地震动参数区划图(GB18306-2015)提供的信息为依托,给出其周边的潜在震源区划分、地震活动性参数及地震动衰减关系,基于地震灾害风险普查资料,利用概率地震危险性分析(CPSHA)方法对其进行地震危险性分析。确定了对从化区地震动峰值加速度起主要贡献的几个潜在震源区及贡献值,计算了从化区未来50年超越概率63%、10%、2%和100年超越概率1%的PGA分布,基于地理信息系统(Geographic Information System,GIS)平台绘制了从化区4种概率下的基岩及地表地震动峰值加速度值分布图。结果表明:背景源(17)、广州、佛冈、河源、担杆岛、珠海和东莞潜在震源区对计算区内PGA起主要贡献;区内50年超越概率10%地表地震动分布中间高两边低。