Mixing Methodologies in Seismic Hazard Assessment via a Logic Tree Procedure: An Application for Eastern Spain     

J. J. Giner  S. Molina  J. Delgado  P. Jáuregui 《Natural Hazards》2002,25(1):59-81

This study provides a procedure for assessing seismic hazardand uncertainties in regions that are characterised by a large non-instrumental earthquakedatabase and a seismic and tectonic behaviour which doesn't allow an evident seismic zonation.This procedure is a synthesis of the non-zoning or non-parametric methodology (using extremevalues distribution functions as proposed by Epstein and Lomnitz, 1966) and the zoning orparametric methodology (using the theorem of total probability as proposed by Cornell, 1968)via a logic tree procedure taking into consideration the advantages offered by each of these.Taking the area which we shall describe as the east coast of Spain and surrounding inland areas,an application was made and a specific logic tree was developed in order to solve the problems anduncertainties related to the evaluation of the seismic hazard using both methodologies. The use of thelogic tree allowed the systematisation of a large number of solutions obtained. A number of relevantresults were obtained which show that in some cases there are great differences in the seismichazard results provided by the non-zoning and the zoning methodologies. In these cases, mean value andstandard deviation of the obtained results provide an intermediate solution to the over-conservativeestimation provided by the non-zoning methodology and the lowest results provided by the zoningmethodology. In other cases results provided by both methodologies are significantly closer.In any case, synthesis among both methodologies gives a wider knowledge of the uncertaintiesassociated with the seismic hazard results. Finally uncertainties increase with the decreaseof the annual probability of exceedence and in sites with a seismic history of large size earthquakes.  相似文献   

Uncertainties in Facies Proportion Estimation I. Theoretical Framework: The Dirichlet Distribution     

André Haas  Philippe Formery 《Mathematical Geology》2002,34(6):679-702

To simulate geological models comprising several litho-types—or facies—we need first to estimate their proportions, which are often poorly known. The corresponding uncertainties can be modelled using a Bayesian approach for inverting the multinomial distribution. The result obtained is known as the Dirichlet distribution. It can be simulated by decomposition into independent conditional distributions. Application of the model is extended to the case of nonstationary proportions and, with some approximation, to the case of correlated spatial data. The mathematical developments presented in the appendices provide a more precise and general definition of the distribution, several decomposition formulae into independent variables, the determination of remarkable stability properties, and the resulting consequences for the conditional and marginal distributions.  相似文献   

Maximum likelihood estimation of Gutenberg-Richterb parameter for uncertain magnitude values     

Andrzej Kijko 《Pure and Applied Geophysics》1988,127(4):573-579

The maximum likelihood estimation of theb parameter in the Gutenberg-Richter relation is extended to the case of uncertain magnitude. An interval which contains the real unknown magnitude is used rather than the uncertain magnitude itself. The proposed approach is very flexible, it allows for the combination of the parts of a catalog of different quality into a single minimally biased set of recurrence parameters.On leave from the Institute of Geophysics, Polish Academy of Sciences, 00-973 Warsaw, Pasteura 3, Poland  相似文献   

The Uncertainty of Mesoscale Numerical Prediction of Heavy Rain in South China and the Ensemble Simulations     

陈静  薛纪善  颜宏 《Acta Meteorologica Sinica》2005,19(1):1-18

1. IntroductionHeavy rain is a kind of severe natural calamitythat influences South China. After decades of years oftests and theoretical exploration by Chinese scientists,significant progresses have been achieved in its predic-tion and basic theoretical studies (Huang, 1986; Xue,1999; Zhou et al., 2003). Currently, the mesoscale nu-merical model has already been employed as one of themajor tools in the prediction and research on heavyrain in South China, promoting considerably the ac-curac…  相似文献   

Spatial-temporal rainfall modelling for flood risk estimation   总被引：4，自引：6，他引：4  

H. S. Wheater  R. E. Chandler  C. J. Onof  V. S. Isham  E. Bellone  C. Yang  D. Lekkas  G. Lourmas  M.-L. Segond 《Stochastic Environmental Research and Risk Assessment (SERRA)》2005,19(6):403-416

Some recent developments in the stochastic modelling of single site and spatial rainfall are summarised. Alternative single site models based on Poisson cluster processes are introduced, fitting methods are discussed, and performance is compared for representative UK hourly data. The representation of sub-hourly rainfall is discussed, and results from a temporal disaggregation scheme are presented. Extension of the Poisson process methods to spatial-temporal rainfall, using radar data, is reported. Current methods assume spatial and temporal stationarity; work in progress seeks to relax these restrictions. Unlike radar data, long sequences of daily raingauge data are commonly available, and the use of generalized linear models (GLMs) (which can represent both temporal and spatial non-stationarity) to represent the spatial structure of daily rainfall based on raingauge data is illustrated for a network in the North of England. For flood simulation, disaggregation of daily rainfall is required. A relatively simple methodology is described, in which a single site Poisson process model provides hourly sequences, conditioned on the observed or GLM-simulated daily data. As a first step, complete spatial dependence is assumed. Results from the River Lee catchment, near London, are promising. A relatively comprehensive set of methodologies is thus provided for hydrological application.  相似文献   

基于微博数据的西藏那曲比如县地震舆情分析     

刘婉婷  杨新月  刘耀辉  魏本勇  齐文华  孙磊 《震灾防御技术》2021,16(4):771-780

震后对网络舆情信息的监控与分析,对于相关部门开展震灾应急救援、掌握救灾动态、稳定民众情绪具有重要意义。本研究基于新浪微博数据,运用网络爬虫技术,获取西藏自治区那曲市比如县6.1级地震震后24小时及震后一周的相关微博及评论;利用Python中文分词组件“jieba”和ROST CM6软件,对数据进行分类、去重、分词等处理,得到结构化的分级、分类数据,并制成震后微博时间序列图、地理分布图、舆情热词词频表、情绪极性统计图等,实现微博舆情数据的可视化。研究结果表明,本次地震事件的微博舆情整体呈现积极情绪,微博活跃程度与当地经济发展程度密切相关。在本次地震舆情传播中,政府部门的舆情引导起到至关重要的作用,舆情传播中的防灾视频传播具有明确的正向引导作用。本研究对于中国西部欠发达少数民族地区的地震舆情分析及引导工作具有借鉴意义。  相似文献   

随机模型上的地震动模拟研究     

余嘉顺  唐红  谢显中 《地震研究》2005,28(1):58-63

介绍了一项随机模拟实验,该实验通过模拟一个具体场址模型的地震动响应了解模型参数不确定性对模拟结果的影响。首先给定一个典型的第四纪沉积层场址模型的参数(包括地层厚度、介质密度、横波速度和品质因子等)的统计特征,并据此在计算机上按截尾的正态分布随机抽样形成了16384个随机模型,然后分别在各个模型上进行SH波地震动响应模拟,最后对所有的模拟结果进行统计分析,了解模型参数的不确定程度与模拟结果变化范围之间的关系。实验结果表明,模型参数不确定性对模拟结果的影响程度是随频率增大的。随机模型地震动响应的第一个放大峰发生在353±031Hz的频率上,其幅值为438±076;第二放大峰发生在885±108Hz的频率上,幅值为422±090。两放大峰值的均方差与均值之比分别为18%和25%。与模型参数20%的相对变化程度大致相当。但更高频率上振幅响应的均方差与均值之比则高达30%～40%。  相似文献   

中全新世以来东亚夏季气温对轨道强迫时空响应不一致的模拟研究          下载免费PDF全文

吴鹏飞  刘征宇  程军  陈广善 《地球物理学报》2014,57(6):1757-1768

基于一个海-气耦合模式FOAM（the Fast Ocean Atmosphere Model）在轨道强迫下对过去6 ka气候变化的瞬变模拟结果,本文分析了中全新世以来东亚地区夏季气温对日射变化的响应特征.研究发现,东亚地区夏季气温对日射响应具有时空不一致性：相对于现代,6 kaB.P.时北半球夏季日射偏强,东亚地区地面气温却未普遍偏高,而是约以35°N为界,北方显著偏暖,南方气温变化不明显甚至有微弱冷却.自6 ka B.P.至今,东亚40°N以北的中、高纬陆地夏季气温大致呈线性降低趋势,以南的低纬陆地夏季气温则呈量级较小的“U”型变化,即气温在约3 kaB.P.附近达最低值,前3 ka为降温趋势,后3 ka为升温趋势.这与一些地质记录反映的气温变化相一致.中全新世以来东亚夏季气温演变的时空不一致性,可能源自因海陆热力惯性不同所引起的气温对日射响应的差异.热容量较小的东亚高纬大陆夏季气温主要响应7月份日射;而热容量较大的海洋对日射的响应通常会滞后约2个月,其夏季气温主要响应5月份日射.受海洋影响,南方陆地夏季气温对日射响应呈现出与海洋相似的特点.在岁差周期上,5、6、7月份日射间的相位差相对于较长轨道时间尺度较不明显,但在相对较短的近6千年时期内,它们相继出现波谷而呈显著趋势差异,从而导致了中全新世以来东亚夏季气温变化的时空差异.正如有学者所指出的,夏季气温变化对应的可能并非同季节日射强迫,考察轨道强迫的气候响应时,如何选择日射标尺至关重要,否则可能混淆“因果”.  相似文献   

Characteristics of tropical Pacific SST predictability in coupled GCM forecasts using the NCEP CFS     

Emilia K. Jin  James L. Kinter III 《Climate Dynamics》2009,32(5):675-691

The limits of predictability of El Niño and the Southern Oscillation (ENSO) in coupled models are investigated based on retrospective forecasts of sea surface temperature (SST) made with the National Centers for Environmental Prediction (NCEP) coupled forecast system (CFS). The influence of initial uncertainties and model errors associated with coupled ENSO dynamics on forecast error growth are discussed. The total forecast error has maximum values in the equatorial Pacific and its growth is a strong function of season irrespective of lead time. The largest growth of systematic error of SST occurs mainly over the equatorial central and eastern Pacific and near the southeastern coast of the Americas associated with ENSO events. After subtracting the systematic error, the root-mean-square error of the retrospective forecast SST anomaly also shows a clear seasonal dependency associated with what is called spring barrier. The predictability with respect to ENSO phase shows that the phase locking of ENSO to the mean annual cycle has an influence on the seasonal dependence of skill, since the growth phase of ENSO events is more predictable than the decay phase. The overall characteristics of predictability in the coupled system are assessed by comparing the forecast error growth and the error growth between two model forecasts whose initial conditions are 1 month apart. For the ensemble mean, there is fast growth of error associated with initial uncertainties, becoming saturated within 2 months. The subsequent error growth follows the slow coupled mode related the model’s incorrect ENSO dynamics. As a result, the Lorenz curve of the ensemble mean NINO3 index does not grow, because the systematic error is identical to the same target month. In contrast, the errors of individual members grow as fast as forecast error due to the large instability of the coupled system. Because the model errors are so systematic, their influence on the forecast skill is investigated by analyzing the erroneous features in a long simulation. For the ENSO forecasts in CFS, a constant phase shift with respect to lead month is clear, using monthly forecast composite data. This feature is related to the typical ENSO behavior produced by the model that, unlike the observations, has a long life cycle with a JJA peak. Therefore, the systematic errors in the long run are reflected in the forecast skill as a major factor limiting predictability after the impact of initial uncertainties fades out.  相似文献   

地震层析成像中的不确定性   总被引：1，自引：0，他引：1  

安美建  冯梅  赵琳 《CT理论与应用研究》2009,18(2):24-32

地震层析成像已经是一种常用的探测地球内部三维波速结构的地球物理方法。这些深部地球结构信息是人们深入认识地球的重要依据,同时由于地表地质过程往往取决于深部动力过程,因此深部结构已经开始受到了地质学家们的广泛重视。但地震层析成像方法众多,所得到的参数和精度可能有所不同,这给非地震学专业的研究人员在使用层析成像结果的过程中造成了极大的不便。为了更好地实现地球物理,地球化学和地质等多学科交叉应用,本文系统分析了地震层析成像结果中可能存在的不确定性,同时提出了相应的建议以帮助地质学家们能够正确对待层析成像结果中的不确定性并合理利用地震层析成像结果。  相似文献