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1.
Probabilistic seismic hazard analysis in Nepal   总被引:3,自引:0,他引:3  
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.  相似文献   

2.
Probabilistic seismic hazard analysis: Early history   总被引:1,自引:0,他引:1  
Probabilistic seismic hazard analysis (PSHA) is the evaluation of annual frequencies of exceedence of ground motion levels (typically designated by peak ground acceleration or by spectral accelerations) at a site. The result of a PSHA is a seismic hazard curve (annual frequency of exceedence vs ground motion amplitude) or a uniform hazard spectrum (spectral amplitude vs structural period, for a fixed annual frequency of exceedence). Analyses of this type were first conceived in the 1960s and have become the basis for the seismic design of engineered facilities ranging from common buildings designed according to building codes to critical facilities such as nuclear power plants. This Historical Note traces the early history of PSHA. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

3.
On unified analysis of uncertainty in seismic hazard assessment   总被引:2,自引:0,他引:2  
(胡聿贤,陈汉尧)Onunifiedanalysisofuncertaintyinseismichazardassessment¥Yu-XianHUandHan-YaoCHEN(InstituteofGeophysics,StateSeismolog...  相似文献   

4.

川滇地区地处我国南北地震带南段,近百年来地震活动性持续较高,该地区未来强震预测研究备受关注.本文根据该区域百年时间内发生的30次MS>6.5历史地震,结合区域地质背景及GPS观测数据等,建立区域有限元准三维弹性模型,通过反演给定区域特定时刻合理的初始应力场.在此基础上,综合考虑地震孕育阶段和震后调整阶段的动力学过程,以库仑-摩尔破裂准则作为判断地震发生的条件,模拟单次地震过程和历史地震序列的发展过程.同时,对于数值模拟中的不确定性成分,通过大量Monte Carlo随机试验得到5000种初始应力场模型,确保所有模型均能重现历史地震的发震过程,最终得到现今应力场状态,并据此计算地震危险性系数,将不同模型的计算结果进行概率统计,初步得到研究区域2017年九寨沟地震后的地震危险性概率分布.结果显示历史地震破裂区的危险性概率大幅降低,相对安全;而龙门山断裂带东北段发震概率高达30%,主要是受2008年汶川地震震后应力扰动的影响;龙门山断裂带西南段(包括汶川地震破裂区与芦山地震破裂区的中间区域)与鲜水河断裂带交界处发震概率约为15%~20%;另外滇西南龙陵瑞丽断裂带及澜沧江断裂带附近发震概率约为10%~15%,近年来滇西南地区小震频发,该地区地震危险性同样值得注意.

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5.
A reliable and homogenized earthquake catalogue is essential for seismic hazard assessment in any area. This article describes the compilation and processing of an updated earthquake catalogue for Pakistan. The earthquake catalogue compiled in this study for the region (quadrangle bounded by the geographical limits 40–83° N and 20–40° E) includes 36,563 earthquake events, which are reported as 4.0–8.3 moment magnitude (MW) and span from 25 AD to 2016. Relationships are developed between the moment magnitude and body, and surface wave magnitude scales to unify the catalogue in terms of magnitude MW. The catalogue includes earthquakes from Pakistan and neighbouring countries to minimize the effects of geopolitical boundaries in seismic hazard assessment studies. Earthquakes reported by local and international agencies as well as individual catalogues are included. The proposed catalogue is further used to obtain magnitude of completeness after removal of dependent events by using four different algorithms. Finally, seismicity parameters of the seismic sources are reported, and recommendations are made for seismic hazard assessment studies in Pakistan.  相似文献   

6.
An improved seismic hazard model for use in performance‐based earthquake engineering is presented. The model is an improved approximation from the so‐called ‘power law’ model, which is linear in log–log space. The mathematics of the model and uncertainty incorporation is briefly discussed. Various means of fitting the approximation to hazard data derived from probabilistic seismic hazard analysis are discussed, including the limitations of the model. Based on these ‘exact’ hazard data for major centres in New Zealand, the parameters for the proposed model are calibrated. To illustrate the significance of the proposed model, a performance‐based assessment is conducted on a typical bridge, via probabilistic seismic demand analysis. The new hazard model is compared to the current power law relationship to illustrate its effects on the risk assessment. The propagation of epistemic uncertainty in the seismic hazard is also considered. To allow further use of the model in conceptual calculations, a semi‐analytical method is proposed to calculate the demand hazard in closed form. For the case study shown, the resulting semi‐analytical closed form solution is shown to be significantly more accurate than the analytical closed‐form solution using the power law hazard model, capturing the ‘exact’ numerical integration solution to within 7% accuracy over the entire range of exceedance rate. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

7.
Two key issues distinguish probabilistic seismic risk analysis of a lifeline or portfolio of structures from that of a single structure. Regional analysis must consider the correlation among lifeline components or structures in the portfolio, and the larger scope makes it much more computationally demanding. In this paper, we systematically identify and compare alternative methods for regional hazard analysis that can be used as the first part of a computationally efficient regional probabilistic seismic risk analysis that properly considers spatial correlation. Specifically, each method results in a set of probabilistic ground motion maps with associated hazard‐consistent annual occurrence probabilities that together represent the regional hazard. The methods are compared according to how replicable and computationally tractable they are and the extent to which the resulting maps are physically realistic, consistent with the regional hazard and regional spatial correlation, and few in number. On the basis of a conceptual comparison and an empirical comparison for Los Angeles, we recommend a combination of simulation and optimization approaches: (i) Monte Carlo simulation with importance sampling of the earthquake magnitudes to generate a set of probabilistic earthquake scenarios (defined by source and magnitude); (ii) the optimization‐based probabilistic scenario method, a mixed‐integer linear program, to reduce the size of that set; (iii) Monte Carlo simulation to generate a set of probabilistic ground motion maps, varying the number of maps sampled from each earthquake scenario so as to minimize the sampling variance; and (iv) the optimization‐based probabilistic scenario again to reduce the set of probabilistic ground motion maps. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

8.
From recent lessons, it is evident that earthquake prediction is immature and impractical as of now. Under the circumstances, seismic hazard analysis is considered a more practical approach for earthquake hazard mitigation, by estimating the annual rate of earthquake ground motions (or seismic hazard) based on seismicity and other geological evidences. Like other earthquake studies for the high-seismicity region around Taiwan, this study aims to conduct a new seismic hazard assessment for the region using the well-established FOSM (first-order second-moment) algorithm, on the record of 55,000 earthquakes observed in the past 110 years. The new seismic hazard analysis from a different perspective shows that the annual rate for earthquake-induced PGA to exceed the current design value (i.e., 0.23g) in two major cities in Taiwan should be relatively low, with it no greater than 0.0006 per year. Besides, the FOSM estimates were found very close to those with Monte Carlo Simulation (MCS), mainly because the skewness of the three random variables (i.e., earthquake magnitude, location, and model error) considered in the probabilistic analysis is not very large.  相似文献   

9.
The distribution of earthquake magnitudes plays a crucial role in the estimation of seismic hazard parameters. Due to the complexity of earthquake magnitude distribution, non-parametric approaches are recommended over classical parametric methods. The main deficiency of the non-parametric approach is the lack of complete magnitude data in almost all cases. This study aims to introduce an imputation procedure for completing earthquake catalog data that will allow the catalog to be used for non-parametric density estimation. Using a Monte Carlo simulation, the efficiency of introduced approach is investigated. This study indicates that when a magnitude catalog is incomplete, the imputation procedure can provide an appropriate tool for seismic hazard assessment. As an illustration, the imputation procedure was applied to estimate earthquake magnitude distribution in Tehran, the capital city of Iran.  相似文献   

10.
This paper describes a methodology to incorporate vague information, based upon heuristic knowledge and expertise, into the conventional probabilistic approach for the seismic hazard analysis.

The interval analysis method is introduced to process interval information with interpretation from Dempster and Shafer's evidence theory. The Vertex Method is discussed to handle fuzzy information which is a generalization of interval information.

These methods, along with the current approach of seismic hazard analysis, are used to assess the seismic hazard for the San Francisco Bay Area in California and to provide information for deciding strengthening policy of existing buildings.  相似文献   


11.
利用概率地震危险性分析(CPSHA)方法,对山东某场地进行地震危险性分析,通过对该场地划分潜在震源区,确定地震活动性参数及地震动衰减关系,计算分析地震危险性概率,基本确定对该场地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,并确定该场地50年超越概率10%的水平向基岩地震动加速度峰值。结果发现,CPSHA方法以具体的构造尺度和更加细致的构造标志来划分潜在震源区,使潜在震源区规模缩减,从而更能反映地震活动在空间分布上的不均匀性。  相似文献   

12.
提出了双场点地震危险性分析方法,用以计算在相同地震构造环境中,相同地震作用下的相邻两个工程场点同时超越其给定地震动参数的概率.该方法是确定系统的危险段落、场点遭受的附加地震危险的有效工具.基于汶川MS8.0地震后大渡河干流及邻近地区的地震环境,以大渡河干流梯级水电站系统为例,确定了大渡河干流梯级水电站各个河段的地震危险性.其中危险性最高的3个河段是:龚嘴—铜街子河段、沙坪—龚嘴河段和大岗山—龙头石河段.  相似文献   

13.
Shear wave velocity modelling in crustal rock for seismic hazard analysis   总被引:2,自引:1,他引:2  
P-wave velocity data along with the thickness of sedimentary and crystalline layers within bedrock were collected from all global regions and presented in the Global Crustal Model CRUST2.0, published in 2001. This well-organised database provides invaluable potential contributions towards future seismic hazard modelling, particularly for stable continental regions (SCRs), where there is a scarcity of representative strong motion records for conventional modelling purposes. The P-wave velocity information presented in CRUST2.0 has been converted herein to S-wave velocity information. The latter is especially important for purposes of seismic hazard modelling. The value of the CRUST2.0 model has therefore been greatly enhanced by the important findings presented and further developed in this paper. By making the best use of available information on crustal conditions, the amplification behaviour of seismic waves affecting a region, an area or a site for any given earthquake scenario may be predicted. The developed methodology, which is intended for worldwide applications, has been illustrated by case studies in which model S-wave velocity profiles were developed for different geological regions within North America. The model profiles were found to be in excellent agreement with field measurements reported for each respective region.  相似文献   

14.
The intterrelation among strong earthquakes and its application are emphatically studied in this paper. Taking North China seismic region as study area, we have investigated how a great earthquake influence other strong earthqukaes in neighbouring area? Does there exist earthqukae immunity phenomenon? If it exists, what distributional pattern did it has in space-time domain? The results show that occurrence of earthquakes withM⩾7 has cetain immunity phenomenon to earthquakes withM⩾6 in North China. Among others, the immunity area of earthquakes withM=8 is much larger than that ofM=7. For earthquakes withM⩾8, the immunity area to the earthquakes ofM=7 is larger than toM=6. Based on the above analysis, using some statistical methods, we gave the variational regularity of seismic immunity factor with space and time, and explored its concrete application in seismic hazard analysis. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 339–346, 1993.  相似文献   

15.
徐伟进  吴健  高孟潭 《地球物理学报》2023,66(12):5005-5018

概率地震危险性分析是地震区划图编制、重大工程场地地震安全性评估以及地震风险管理等领域的重要依据,地震时间活动性模型则是概率地震危险性分析的主要理论基础.本研究中基于布朗过程时间(Brownian passage time(BPT))模型,计算了不同情况下中国大陆特征地震震源区时间相依的地震发生率,采用概率地震危险性计算方法,选择合适的地震动模型,评估了中国大陆地区时间相依的地震危险性,并与基于泊松模型的地震危险性做了比较.结果表明,时间相依的地震活动特征对概率地震危险性具有显著影响,在那些地震离逝时间相对较长,离逝率较大(大于1)的震源区,时间相依的地震危险性结果相较于基于泊松模型的地震危险性结果显著增大,增大幅度最大可达50%以上.相反,在那些刚发生地震不久,地震离逝时间较短的震源区,时间相依的地震危险性结果相较于泊松模型显著减小,减小幅度最大可达50%左右.地震复发间隔的变异系数对地震危险性结果也有显著影响,选择合适的变异系数对时间相依地震危险性分析十分重要,后续应该加强对地震复发间隔不确定性的研究.研究结果还表明,时间相依的地震活动特征对不同超越概率下的地震危险性结果的影响是一致的,不随超越概率水平的变化而变化.本文研究结果对地震风险管理、地震保险以及相关防震减灾政策的制定等方面具有重要的应用价值.

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16.
A project has been implemented in recent years for assessing seismic hazard in the Italian territory on probabilistic bases, to be used as scientific background for the revision of the current seismic zonation. A consolidated approach was considered for the purpose; seismic hazard was estimated in terms of peak ground acceleration and macroseismic intensity. As the computer code employed allows the user to make specific choices on some input data, some rather unorthodox decisions were taken regarding earthquake catalogue completeness, seismicity rates, boundaries of the seismogenic zones, definition of the maximum magnitude, attenuation relation, etc. The overwhelming amount of geological and seismological data for Italy (just consider, for example, that the earthquake catalogue collects events which occurred over the last ten centuries) permits the operator to make different choices, more or less cautiously. It is quite interesting, then, to evaluate the influence of the specific choices on the final hazard results as a comparison to traditional possibilities. The tests performed clearly indicate the critical choices and quantify their contribution. In particular, we consider thorough comprehension of the space geometry of the earthquake source boundaries and the adequacy of the attenuation relation in modelling the radiation pattern very important.  相似文献   

17.
A mature mathematical technique called copula joint function is introduced in this paper, which is commonly used in the financial risk analysis to estimate uncertainty. The joint function is generalized to the n-dimensional Frank’s copula. In addition, we adopt two attenuation models proposed by YU and Boore et al, respectively, and construct a two-dimensional copula joint probabilistic function as an example to illustrate the uncertainty treatment at low probability. The results show that copula joint func...  相似文献   

18.
Statistical modeling of ground motion relations for seismic hazard analysis   总被引:1,自引:0,他引:1  
We introduce a new approach for ground motion relations (GMR) in the probabilistic seismic hazard analysis (PSHA), being influenced by the extreme value theory of mathematical statistics. Therein, we understand a GMR as a random function. We derive mathematically the principle of area equivalence, wherein two alternative GMRs have an equivalent influence on the hazard if these GMRs have equivalent area functions. This includes local biases. An interpretation of the difference between these GMRs (an actual and a modeled one) as a random component leads to a general overestimation of residual variance and hazard. Beside this, we discuss important aspects of classical approaches and discover discrepancies with the state of the art of stochastics and statistics (model selection and significance, test of distribution assumptions, extreme value statistics). We criticize especially the assumption of logarithmic normally distributed residuals of maxima like the peak ground acceleration (PGA). The natural distribution of its individual random component (equivalent to exp(ε 0) of Joyner and Boore, Bull Seism Soc Am 83(2):469–487, 1993) is the generalized extreme value. We show by numerical researches that the actual distribution can be hidden and a wrong distribution assumption can influence the PSHA negatively as the negligence of area equivalence does. Finally, we suggest an estimation concept for GMRs of PSHA with a regression-free variance estimation of the individual random component. We demonstrate the advantages of event-specific GMRs by analyzing data sets from the PEER strong motion database and estimate event-specific GMRs. Therein, the majority of the best models base on an anisotropic point source approach. The residual variance of logarithmized PGA is significantly smaller than in previous models. We validate the estimations for the event with the largest sample by empirical area functions, which indicate the appropriate modeling of the GMR by an anisotropic point source model. The constructed distances like the Joyner–Boore distance do not work well for event-specific GMRs. We discover also a strong relation between magnitude and the squared expectation of the PGAs being integrated in the geo-space for the event-specific GMRs. One of our secondary contributions is the simple modeling of anisotropy for a point source model.  相似文献   

19.
The characterisation of the seismic hazard input is a critical element of any seismic design code, not only in terms of the absolute levels of ground motion considered but also of the shape of the design spectrum. In the case of Europe, future revisions of the seismic design provisions, both at a national and a pan‐European level, may implement considerable modifications to the existing provisions in light of recent seismic hazard models, such as the 2013 European Seismic Hazard Model. Constraint of the shape of the long‐period design spectrum from seismic hazard estimates on such a scale has not been possible, however, owing to the limited spectral period range of existing ground motion models. Building upon recent developments in ground motion modelling, the 2013 European Seismic Hazard Model is adapted here with a new ground motion logic tree to provide a broadband Probabilistic Seismic Hazard Analysis for rock sites across a spectral period range from 0.05 seconds to 10.0 seconds. The resulting uniform hazard spectra (UHS) are compared against existing results for European and broadband Probabilistic Seismic Hazard Analysis and against a proposed formulation of a generalised design spectrum in which controlling parameters can be optimised to best fit the uniform hazard spectra in order to demonstrate their variability on a European scale. Significant variations in the controlling parameters of the design spectrum are seen both across and within stable and active regions. These trends can help guide recalibrations of the code spectra in future revisions to seismic design codes, particularly for the longer‐period displacement spectrum.  相似文献   

20.
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