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1.
Truncation of the distribution of ground-motion residuals 总被引:1,自引:3,他引:1
Recent studies to assess very long-term seismic hazard in the USA and in Europe have highlighted the importance of the upper
tail of the ground-motion distribution at the very low annual frequencies of exceedance required by these projects. In particular,
the use of an unbounded lognormal distribution to represent the aleatory variability of ground motions leads to very high
and potentially unphysical estimates of the expected level of shaking. Current practice in seismic hazard analysis consists
of truncating the ground-motion distribution at a fixed number (ε
max) of standard deviations (σ). However, there is a general lack of consensus regarding the truncation level to adopt. This paper investigates whether
a physical basis for choosing ε
max can be found, by examining records with large positive residuals from the dataset used to derive one of the ground-motion
models of the Next Generation Attenuation (NGA) project. In particular, interpretations of the selected records in terms of
causative physical mechanisms are reviewed. This leads to the conclusion that even in well-documented cases, it is not possible
to establish a robust correlation between specific physical mechanisms and large values of the residuals, and thus obtain
direct physical constraints on ε
max. Alternative approaches based on absolute levels of ground motion and numerical simulations are discussed. However, the choice
of ε
max is likely to remain a matter of judgment for the foreseeable future, in view of the large epistemic uncertainties associated
with these alternatives. Additional issues arise from the coupling between ε
max and σ, which causes the truncation level in terms of absolute ground motion to be dependent on the predictive equation used. Furthermore,
the absolute truncation level implied by ε
max will also be affected if σ is reduced significantly. These factors contribute to rendering a truncation scheme based on a single ε
max value impractical. 相似文献
2.
John Douglas Hideo Aochi Peter Suhadolc Giovanni Costa 《Bulletin of Earthquake Engineering》2007,5(1):17-26
In this short article, the possible reduction in the standard deviation of empirical ground motion estimation equations through
the modelling of the effect of crustal structure is assessed through the use of ground-motion simulations. Simulations are
computed for different source-to-site distances, focal depths, focal mechanisms and for crustal models of the Pyrenees, the
western Alps and the upper Rhine Graben. Through the method of equivalent hypocentral distance introduced by Douglas et al.
[(2004) Bull Earthquake Eng 2(1): 75–99] to model the effect of crustal structure in empirical equations, the scatter associated
with such equations derived using these simulated data could be reduced to zero if real-to-equivalent hypocentral distance
mapping functions were derived for every combination of mechanism, depth and crustal structure present in the simulated dataset.
This is, obviously, impractical. The relative importance of each parameter in affecting the decay of ground motions is assessed
here. It is found that variation in focal depth is generally more important than the effect of crustal structure when deriving
the real-to-equivalent hypocentral distance mapping functions. In addition, mechanism and magnitude do not have an important
impact on the decay rate. 相似文献
3.
随着川滇地区强震记录的不断增加,为了建立更符合该区域地震动特征的预测模型,文中基于该区域现有的地震动数据,通过随机效应回归模型建立适用于川滇地区的地震动预测模型;2021年5月21日,云南省大理州漾濞县发生6.4级地震,为了分析文中预测模型对漾濞地震的适用性,首先根据预测模型的适用范围选取合适的漾濞地震数据,计算真实记... 相似文献
4.
青海地区强震活动的统计分析及预报探讨 总被引:2,自引:0,他引:2
从统计的角度出发,研究了青海地区1993年M≥6强震的发生概率,在此基础上应用非线性最小二乘法拟合的Gompertz与Logistic曲线模型以及可公度模型对该区M≥6.5强震进行了预测探索。结果表明,1993年该地区M≥6强震的发生概率将达到0.76-0.87,1993-1994年有可能发生M≥6.5强震。 相似文献
5.
6.
湖北西部地区小震活动与台湾强震关系研究 总被引:1,自引:1,他引:1
简要阐述了湖北西部地区地震活动和台湾地区强震活动特征, 研究了1981年以来湖北西部地区弱震和台湾地区6级以上强震发生的关系。 结果表明, 二个地区地震活动有较好的相关性。 根据这种相关性实现对台湾强震的临震预测, 对应率较高, 预报效能较好。 相似文献
7.
John Douglas Sinan Akkar Gabriele Ameri Pierre-Yves Bard Dino Bindi Julian J. Bommer Sanjay Singh Bora Fabrice Cotton Boumédiène Derras Marcel Hermkes Nicolas Martin Kuehn Lucia Luzi Marco Massa Francesca Pacor Carsten Riggelsen M. Abdullah Sandıkkaya Frank Scherbaum Peter J. Stafford Paola Traversa 《Bulletin of Earthquake Engineering》2014,12(1):341-358
This article presents comparisons among the five ground-motion models described in other articles within this special issue, in terms of data selection criteria, characteristics of the models and predicted peak ground and response spectral accelerations. Comparisons are also made with predictions from the Next Generation Attenuation (NGA) models to which the models presented here have similarities (e.g. a common master database has been used) but also differences (e.g. some models in this issue are nonparametric). As a result of the differing data selection criteria and derivation techniques the predicted median ground motions show considerable differences (up to a factor of two for certain scenarios), particularly for magnitudes and distances close to or beyond the range of the available observations. The predicted influence of style-of-faulting shows much variation among models whereas site amplification factors are more similar, with peak amplification at around 1s. These differences are greater than those among predictions from the NGA models. The models for aleatory variability (sigma), however, are similar and suggest that ground-motion variability from this region is slightly higher than that predicted by the NGA models, based primarily on data from California and Taiwan. 相似文献
8.
9.
IntroductionThe development and occurrence of macroseismic activity come from the specific structUreenvironment and stress condition. So the space-time distribUtion of strong quakes appears to bevery inhomogeneous. Earthquakes with Ms27.0 in a seismicity period presented often a speeding-up pattern with time in different seismic provinces. That is, the cumulative frequency of earthquakes with Ms27.0 increase with exponent N(t)=ae', in a seismicity period (ZHANG, FU, 1989).It means that t… 相似文献
10.
In order to estimate the recurrence intervals for large earthquakes occurring in eastern Anatolia, this region enclosed within
the coordinates of 36∘–42∘N, 35∘–45∘E has been separated into nine seismogenic sources on the basis of certain seismological and geomorphological criteria, and
a regional time- and magnitude-predictable model has been applied for these sources. This model implies that the magnitude
of the preceding main shock which is the largest earthquake during a seismic excitation in a seismogenic source governs the
time of occurrence and the magnitude of the expected main shock in this source. The data belonging to both the instrumental
period (MS≥ 5.5) until 2003 and the historical period (I0≥ 9.0 corresponding to MS≥ 7.0) before 1900 have been used in the analysis. The interevent time between successive main shocks with magnitude equal
to or larger than a certain minimum magnitude threshold were considered in each of the nine source regions within the study
area. These interevent times as well as the magnitudes of the main shocks have been used to determine the following relations:
fwawhere Tt is the interevent time measured in years, Mmin is the surface wave magnitude of the smallest main shock considered, Mp is the magnitude of the preceding main shock, Mf is magnitude of the following main shock, and M0 is the released seismic moment per year in each source. Multiple correlation coefficient and standard deviation have been
computed as 0.50 and 0.28, respectively for the first relation. The corresponding values for the second relation are 0.64
and 0.32, respectively. It was found that the magnitude of the following main shock Mf does not depend on the preceding interevent time Tt. This case is an interesting property for earthquake prediction since it provides the ability to predict the time of occurrence
of the next strong earthquake. On the other hand, a strong negative dependence of Mf on Mp was found. This result indicates that a large main shock is followed by a smaller magnitude one and vice versa. On the basis
of the first one of the relations above and taking into account the occurrence time and magnitude of the last main shock,
the probabilities of occurrence P(Δ t) of main shocks in each seismogenic source of the east Anatolia during the next 10, 20, 30, 40 and 50 years for earthquakes
with magnitudes equal 6.0 and 7.0 were determined. The second of these relations has been used to estimate the magnitude of
the expected main shock. According to the time- and magnitude-predictable model, it is expected that a strong and a large
earthquake can occur in seismogenic Source 2 (Erzincan) with the highest probabilities of P10 = 66% (Mf = 6.9 and Tt = 12 years) and P10 = 44% (Mf = 7.3 and Tt = 24 years) during the future decade, respectively. 相似文献
11.
12.
A. Joshi 《Journal of Seismology》2000,4(2):143-160
The rupture plane for an earthquake has been modelledby using the semi empirical technique of Midorikawa(1993). This technique estimates ground accelerationby modelling the rupture process during an earthquake.Modifications in this technique have been made for itsapplication to the Indian region. This has been tested forthe Uttarkashi earthquake of 20th Oct, 1991, India, whichwas well recorded at thirteen stations of installedstrong motion array in this region. After testingseveral possible rupture models, a final model has beenselected and peak ground acceleration due to thismodel is simulated at thirteen different stations.Dependency of methodology on model parameters, e.g.dip and mode of rupture propagation have also beenstudied in detail.Using this technique synthetic isoseismal maps wereprepared by converting peak ground acceleration intoMMI scale. Dependency of rupture models on syntheticisoseismals has also been studied in detail. Usingthis method, peak ground acceleration for the Laturearthquake of Sept 30, 1993 has been obtained atvarious places within meisoseismal area. Synthetic andfield intensity was compared at various well-knownsites. Since the region was not covered by anyinstrumental array during Latur earthquake, thesimulated peak ground accelerations are expected toserve basis of design criteria in this region. 相似文献
13.
A review of rock mechanics studies in the United States pertinent to earthquake prediction 总被引:1,自引:0,他引:1
J. Byerlee 《Pure and Applied Geophysics》1978,116(4-5):586-602
Premonitory phenomena such as dilatancy, creep, acoustic emission, and changes in seismic velocity and attenuation, electrical resistivity, magnetic moment, and gas emission, which occur before fracture of initially intact rock and before stick-slip on faults or between finely ground surfaces of rock, have been reviewed and discussed in relation to earthquake prediction. This review is restricted to the results of laboratory experiments that have been carried out in the United States of America. 相似文献
14.
The thermal pollution patch of Hadera power plant was used as a natural laboratory to evaluate the potential long-term effects of rise in Eastern Mediterranean SST on living benthic foraminifera. Their sensitivity to environmental changes makes foraminifera ideal for this study. Ten monthly sampling campaigns were performed in four stations located along a temperature gradient up to 10 °C from the discharge site of heated seawater to a control station. The SST along this transect varied between 25/18 °C in winter and 36/31 °C in summer. A significant negative correlation was found between SST in all stations and benthic foraminiferal abundance, species richness and diversity. The total foraminiferal abundance and species richness was particularly low at the thermally polluted stations especially during summer when SST exceeded 30 °C, but also throughout the entire year. This indicates that thermal pollution has a detrimental effect on benthic foraminifera, irrelevant to the natural seasonal changes in SST. 相似文献
15.
16.
华北地区强震前兆空间动态场中短期综合预报研究 总被引:1,自引:0,他引:1
通过80多种测震学指标的筛选和多种稳定性试验,探索以一种新的指标筛选法-“对比筛选法”选取地震学单参数,在此基础上提取地震学综合预报指标P值。由此,发展了一种新的测震学的定量综合预报方法SQIP。同时研究了非测震学前兆综合指标PP值的确定和应用效果检验及其空间扫描的动态显示,尝试了震兆指标和前兆指标联合应用于地震预报的研究。以动态的思维逻辑不断追踪地震活动的异常行为,判定地震在中短期的危险地点。就 相似文献
17.
SLG地区天然气资源量丰富,是我国油气增储上产的重要区域,利用叠后地震描述进行储层预测时多解性很强.本文针对SLG地区盒8段储层,充分利用了叠前地震资料信息丰富的特点,以AVO模型正演技术为基础,研究含气砂岩的地球物理响应特征.利用弹性波阻抗反演和叠前同步反演等技术,开展了叠前储层预测和含气性检测,形成了叠前地震描述技术系列.实际钻探结果表明,预测结果的精度较高,表明利用叠前地震描述技术进行SLG地区盒8段储层预测是可行的. 相似文献
18.
作为强震长期预测基础的地震带、潜在震源区的划分,仍然依据地震构造类比和地震活动重复两原则。现有的强震长期预测方法在构造“稳定”区,即没有活动构造、没有历史地震(包括古地震)资料的条件下,无能为力。通过张北地震资料的分析,高精度地震定位并结合波形数据反演震源机制的结果表明:在稳定而统一的构造应力场的作用下,沿其最大剪切应力方向上的小地震集中成带,并且持续活动、震源机制的优势取向与应力场吻合,小震带便可以看作属于现今活动的震源断层,在地震长期预测工作中可以作为划分潜在震源区的依据。构造“稳定”区发生的强震属于新破裂。 相似文献
19.
20.
在波谱分析的基础上,对广东地区75个地震的波谱和震源参数进行了研究和探讨,侧重研究了它们与地震强度的关系,初步结果表明:地震波谱和震源参数的震源半径,地震矩,应力降,平均位错,环境剪切应力,它们与地震的震级的相关性十分密切,主要表现在当震级小于ML3.8时,应力降、平均位错、环境剪切应力的对数跟震级呈现明显的正相关,而拐角频率、震源半径则与震级无关;反之,当震级大于ML3.8时,拐角频率、震源半径的对数则与震级又表现出很强的相关性,而应力降、平均位错、环境剪切应力与震级相关性不显著。上述结果说明,用地震波谱和震源参数开展地震预报研究必须十分注意它们与地震强度彼此的相关性问题,否则会对异常的判别造成很大的影响,从而得出错误的结果。 相似文献