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1.
中国南北地震带是一个强震密集,人所注目的地区。本文以南北带北端地震活动性资料为基础,检验模糊数学中的信息检索方法预报地震的效果。对于一个待报时间段,方法选用相应的三个资料时间段范围,选取若干个地震活动性指标,如:相邻两个资料时间段中发生地震(M≥5)次数比N2/N1,发生地震次数随时间的变化量$ \dot{N} $,平均震级(M)及其随时间的变化量($ \dot{\bar{M}} $)。地震强度分类情况为:(1)类:M≤5.7;(2)类:5.8≤M6.7;(3)类:6.8≤M≤7.7;(4)类:7.8≤M。用模糊集理论进行待报时间段与该时间段中将发生地震类别的匹配过程,从而确定某时间段中可能发生的最大地震强度。本文选用的基础资料从十六世纪开始,范围限于南北带的北段。在对十七世纪以后的资料进行检验后,初步结果表明,检验结果较好。并对今后十年左右发生强震的可能性作了初步估计。 相似文献
2.
Earthquake Researeh in Ch一na461 .METHODLet R be some value measured or estimated as a sequenee ina’‘Past”time interval(一丁,O)(I)万‘月,=(RI,…,R。),R,之R。,R=nlaX l二f匕11(RI,…,R,,) Values(l)eould have an arbitrary Physieal nature.BelowweshalleonsiderEq.(l)asearthquakemagnitudes in a given seismic aetive region or logarithms of seismie Peak ground aeeelerations at习given site.Ro isa而nimum eutoff value;it 15 defined by Possibilities of registration systems or wasehosen as the … 相似文献
3.
To actually reflect the seismic temporal-spatial inhomogeneity of intra continental strong earthquakes of North China in seismic
hazard analysis, several seismological and geological characteristics have been selected and quantized to describe the seismicity
features in time and space of every magnitude interval with the thought of dividing the interesting magnitude range into several
intervals and using of spatial probability distribution function. A component analysis method with orthogonal transformation
is introduced to avoid the repeated use of the same element and the subjective effects in determining the annual earthquake
occurrence rates of earthquake. By passing synthetic fuzzy judgement on the nonintercorrelated new characteristics, the annual
occurrence rates of every magnitude interval of each potential source area are obtained associated with the adjustments of
earthquake reducing process after the occurrence ofM>7 quake. An intensity map of the Beijing-Tianjin-Zhangjiakou area is calculated as an example which shows a close coincidence
with the seismic temporal-spatial inhomogeneity of North China.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 496–504, 1991. 相似文献
4.
由中国大陆板块内部地震活动与其周缘地震活动的相关性,可以确定我国大陆未来地震活动的主体和地震活动高潮时间[1].在此基础上,本文进一步探讨用长时间、大面积的地震活动信息,对重点监测区未来地震作出时、空、强综合评判.全文分为三部分:1.地震强度的预报.对于确定的能有效地估计未来地震强度的5项地震活动性指标,选择加权平均型的模糊综合评判方法,对监测区未来地震的震级给出明确的结果.2.发震地点预报.对于扫描单元定义了反映b值时空变化的二项指标:b值异常次数Ayi;和b值异常均值byi.通过对二项指标空间分布的综合分析,可以估计未来地震发生的地点.3.发震时间预报.把缺震时间Tl与b值回升时间Tbu,作为描述大震前平静过程的二项定量指标.在对未来地震强度作出模糊综合评判后,可用Tl,Tbu二项指标综合推断监测区未来地震发生的时间.总结的九个震例结果表明,该方法可使地震预报定量化、实用化,可以用于地震形势的预测和中、短期地震预报. 相似文献
5.
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
6.
在十年尺度（５—１０年）地震危险性预测中，需要处理众多的不确定因素。受这些不确定因素的约束，地震预测的结果必然带有相当的不确定性，因此应该用概率分析的方法进行预测。考虑地震发生的时间、空间和强度的非均匀性及相关特征和地震危险性长期背景（地质、地球物理场等因素）与地震发生前兆的概率结合，提出了十年尺度地震危险性预测的概率模型。考虑资料的不均匀性和适宜不同地区的地震前兆方法的差异，本文还提出了概率预测模型简化形式，以满足全国不同地区的需要。本文以华北北部地区为例讨论了该模型的实际应用。文中提出的方法可以用于全国十年尺度地震危险性的概率预测。根据本项研究提供的结果和计算程序，可以满足地震对策和地震损失估计对地震中长期概率预测的需要。 相似文献
7.
为了在地震危险性分析方法中,较好地反映大陆内部地震活动的时空不均匀性,按照震级分档和空间概率分布函数的思路,本文选取并量化了多个地震、地质特征,以描述各震级档地震活动在时间上和空间上的性质.为避免同一因素的重复使用和主观作用的介入,文中引入了分量分析方法对特征进行正交变换.对变换得到的互不相关的新特征进行模糊综合评判,再结合七级以上强震发生后的减震作用,确定了各潜在震源区各震级档的地震年平均发生率作为例子,试算了京-津-唐-张地区的地震烈度区划图.该例子说明,本文的分析方法,不仅能反映华北地区地震活动的时空不均匀性,还避免了特征量的重复使用和专家判断的影响 相似文献
8.
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
9.
Ram Bichar Singh Yadav Jayant Nath Tripathi Bal Krishna Rastogi Sumer Chopra 《Pure and Applied Geophysics》2008,165(9-10):1813-1833
The Gujarat and adjoining region falls under all four seismic zones V, IV, III and II of the seismic zoning map of India, and is one of the most seismically prone intracontinental regions of the world. It has experienced two large earthquakes of magnitude M w 7.8 and 7.7 in 1819 and 2001, respectively and several moderate earthquakes during the past two centuries. In the present study, the probability of occurrence of earthquakes of M ≥ 5.0 has been estimated during a specified time interval for different elapsed times on the basis of observed time intervals between earthquakes using three stochastic models namely, Weibull, Gamma and Lognormal. A complete earthquake catalogue has been used covering the time interval of 1819 to 2006. The whole region has been divided into three major seismic regions (Saurashtra, Mainland Gujarat and Kachchh) on the basis of seismotectonics and geomorphology of the region. The earthquake hazard parameters have been estimated using the method of maximum likelihood. The logarithmic of likelihood function (ln L) is estimated and used to test the suitability of models in three different regions. It was found that the Weibull model fits well with the actual data in Saurashtra and Kachchh regions, whereas Lognormal model fits well in Mainland Gujarat. The mean intervals of occurrence of earthquakes are estimated as 40.455, 20.249 and 13.338 years in the Saurashtra, Mainland Gujarat and Kachchh region, respectively. The estimated cumulative probability (probability that the next earthquake will occur at a time later than some specific time from the last earthquake) for the earthquakes of M ≥ 5.0 reaches 0.9 after about 64 years from the last earthquake (1993) in Saurashtra, about 49 years from the last earthquake (1969) in Mainland Gujarat and about 29 years from the last earthquake (2006) in the Kachchh region. The conditional probability (probability that the next earthquake will occur during some specific time interval after a certain elapsed time from last earthquake) is also estimated and it reaches about 0.8 to 0.9 during the time interval of about 57 to 66 years from the last earthquake (1993) in Saurashtra region, 31 to 51 years from the last earthquake (1969) in Mainland Gujarat and about 21 to 28 years from the last earthquake (2006) in Kachchh region. 相似文献
10.
收集了湖北省数字测震台网2007—2015年记录到的数字地震波形,利用震相清晰的台站测定了地方震震级,并计算了其与中国地震台网中心公布震级的偏差.在此基础上,以每个数字测震台站为中心,按照每30°为一个区间,将每个台站记录到的地震事件分为12个区间,对每个区间的平均震级偏差和标准离差予以统计分析.结果显示,除去24个无地震事件区间,300个区间的平均震级偏差中,81.7%的偏差小于0.3;再除去14个样本数为1的区间,其余286个区间的方位标准离差中,98.3%的离差小于0.5.经校正后各区间的平均震级偏差和方位标准离差均有所下降,表明地震传播方位对地方震震级测定的影响有所降低.因此,针对数字测震台站对不同方位地震所测定的震级偏差存在的差异进行相应校正是必要且有意义的. 相似文献
11.
Many uncertainty factors need be dealt with in the prediction of seismic hazard for a 10-year period.Restricted by these uncertainties,the result of prediction is also uncertain to a certain extent,so the probabilistic analysis method of seismic hazard should be adopted.In consideration of the inhomogeneity of the time,location,and magnitude of future earthquakes and the probabilistic combination of the background of long-term seismic hazard(geology,geophysical field,etc.)and the precursors of earthquake occurrence,a model of probabilistic prediction of seismic hazard in a period of 10 years s proposed.Considering the inhomogeneity of data and earthquake precursors for different regions in China,a simplified model is also proposed in order to satisfy the needs of different regions around the country.A trial in North China is used to discuss the application of the model.The method proposed in this paper can be used in the probabilistic prediction of seismic hazard in a period of 10 years.According to the 相似文献
12.
Probabilistic Appraisal of Earthquake Hazard Parameters Deduced from a Bayesian Approach in the Northwest Frontier of the Himalayas 总被引：5，自引：0，他引：5
R. B. S. Yadav T. M. Tsapanos Yusuf Bayrak G. Ch. Koravos 《Pure and Applied Geophysics》2013,170(3):283-297
A straightforward Bayesian statistic is applied in five broad seismogenic source zones of the northwest frontier of the Himalayas to estimate the earthquake hazard parameters (maximum regional magnitude M max, β value of G–R relationship and seismic activity rate or intensity λ). For this purpose, a reliable earthquake catalogue which is homogeneous for M W ≥ 5.0 and complete during the period 1900 to 2010 is compiled. The Hindukush–Pamir Himalaya zone has been further divided into two seismic zones of shallow (h ≤ 70 km) and intermediate depth (h > 70 km) according to the variation of seismicity with depth in the subduction zone. The estimated earthquake hazard parameters by Bayesian approach are more stable and reliable with low standard deviations than other approaches, but the technique is more time consuming. In this study, quantiles of functions of distributions of true and apparent magnitudes for future time intervals of 5, 10, 20, 50 and 100 years are calculated with confidence limits for probability levels of 50, 70 and 90 % in all seismogenic source zones. The zones of estimated M max greater than 8.0 are related to the Sulaiman–Kirthar ranges, Hindukush–Pamir Himalaya and Himalayan Frontal Thrusts belt; suggesting more seismically hazardous regions in the examined area. The lowest value of M max (6.44) has been calculated in Northern-Pakistan and Hazara syntaxis zone which have estimated lowest activity rate 0.0023 events/day as compared to other zones. The Himalayan Frontal Thrusts belt exhibits higher earthquake magnitude (8.01) in next 100-years with 90 % probability level as compared to other zones, which reveals that this zone is more vulnerable to occurrence of a great earthquake. The obtained results in this study are directly useful for the probabilistic seismic hazard assessment in the examined region of Himalaya. 相似文献
13.
-- We investigate the impact of different rupture and attenuation models for the Cascadia subduction zone by simulating seismic hazard models for the Pacific Northwest of the U.S. at 2% probability of exceedance in 50 years. We calculate the sensitivity of hazard (probabilistic ground motions) to the source parameters and the attenuation relations for both intraslab and interface earthquakes and present these in the framework of the standard USGS hazard model that includes crustal earthquakes. Our results indicate that allowing the deep intraslab earthquakes to occur anywhere along the subduction zone increases the peak ground acceleration hazard near Portland, Oregon by about 20%. Alternative attenuation relations for deep earthquakes can result in ground motions that differ by a factor of two. The hazard uncertainty for the plate interface and intraslab earthquakes is analyzed through a Monte-Carlo logic tree approach and indicates a seismic hazard exceeding 1 g (0.2 s spectral acceleration) consistent with the U.S. National Seismic Hazard Maps in western Washington, Oregon, and California and an overall coefficient of variation that ranges from 0.1 to 0.4. Sensitivity studies indicate that the paleoseismic chronology and the magnitude of great plate interface earthquakes contribute significantly to the hazard uncertainty estimates for this region. Paleoseismic data indicate that the mean earthquake recurrence interval for great earthquakes is about 500 years and that it has been 300 years since the last great earthquake. We calculate the probability of such a great earthquake along the Cascadia plate interface to be about 14% when considering a time-dependent model and about 10% when considering a time-independent Poisson model during the next 50-year interval. 相似文献
14.
Time probabilistic evaluation of seismically induced landslide hazard in Irpinia (Southern Italy) 总被引：2，自引：0，他引：2
A recently proposed method, which incorporates the Newmark model to evaluate the earthquake-induced landslide hazard at regional scale, was applied to Irpinia, one of the most seismically active regions of Italy. The method adopts a probabilistic approach to calculate values of critical acceleration ac representing the minimum strength required for a slope not to fail at a fixed probability level in a given time interval. Regional probabilistic hazard maps were generated for the two failure types most common in Irpinia (slump–earthflows and rock falls). The results suggest that quite moderate critical acceleration (0.05–0.08 g) could suffice to keep the slope failure probability low. However, the available data indicate that potential slide surfaces with ac below these values could be common in Irpinia, where, perhaps in relation to particular geo-environmental conditions, a relative large number of marginally stable slopes might survive other destabilising actions and fail even on occasion of not particularly strong earthquake shaking. 相似文献
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16.
Ruifang Yu Yisheng Song Xiangyun Guo Qianli Yang Xinjuan He Yanxiang Yu 《地震科学（英文版）》2022,35(5):314-328
Seismic hazard analyses are mainly performed using either deterministic or probabilistic methods. However, there are still some defects in these statistical model-based approaches for regional seismic risk assessment affected by the near-field of large earthquakes. Therefore, we established a deterministic seismic hazard analysis method that can characterize the entire process of ground motion propagation based on stochastic finite-fault simulation, and we chose the site of the Xiluodu dam to demonstrate the method. This method can characterize earthquake source properties more realistically than other methods and consider factors such as the path and site attenuation of seismic waves. It also has high computational efficiency and is convenient for engineering applications. We first analyzed the complexity of seismogenic structures in the Xiluodu dam site area, and then an evaluation system for ground motion parameters that considers various uncertainties is constructed based on a stochastic finite-fault simulation. Finally, we assessed the seismic hazard of the dam site area comprehensively. The proposed method was able to take into account the complexity of the seismogenic structures affecting the dam site and provide multi-level parameter evaluation results corresponding to different risk levels. These results can be used to construct a dam safety assessment system of an earthquake in advance that provides technical support for rapidly and accurately assessing the post-earthquake damage state of a dam, thus determining the influence of an earthquake on dam safety and mitigating the risk of potential secondary disasters. 相似文献
17.
Assessing current faulting behaviors and seismic risk of the Anninghe-Zemuhe fault zone from seismicity parameters 总被引：6，自引：0，他引：6
Introduction Strong and large earthquakes are prepared and generated on specific segments of active fault zones, especially on the asperity parts of the zones (Aki, 1984; Wiemer, Wyss, 1997; Wyss, et al, 2000). Therefore, both the faulting-behavior identification and the rupture segmentation mainly based on the method of active tectonics are always important aspects in active fault research (DING, et al, 1993). The purposes of the two aspects of research focus on determining fault units tha… 相似文献
18.
利用区域台网地震资料, 分析了川西安宁河-则木河断裂带不同段落的现今活动习性，进而鉴别潜在大地震危险的断裂段. 文中由异常低b值的分布圈绘出凹凸体，发展和应用了由多个地震活动参数值的组合判定断裂分段活动习性的方法，尝试了利用凹凸体段的震级频度关系参数估计特征地震的平均复发间隔. 结果表明，该研究断裂带存在5个不同现今活动习性的段落. 其中，安宁河断裂的冕宁-西昌段属于高应力下的闭锁段，其核心部分为一较大尺度的凹凸体；则木河断裂的西昌-普格段则表现为低应力下的微弱活动状态. 重新定位的震源深度分布，显示出上述闭锁段和微弱活动段的断层面轮廓. 冕宁-西昌段是未来大地震的潜在危险段. 该段从最晚的1952年6.7级地震起算，至未来特征地震的平均复发间隔估值为55～67年, 未来地震的震级估值为7.0～7.5. 本研究也初步表明，同-断裂段的活动习性可随时间动态演变. 相似文献
19.
冀鲁豫交界区地下流体模糊熵值的变化与地震的关系 总被引：3，自引：0，他引：3
采用概率化预处理方法，把冀鲁豫交界区地下流体多种观测项目的观测值转化为概率值时间序列，然后计算其模糊从属函数。在此基础上计算该区地下流体构成的信息源系统的模糊熵值，分析了模糊熵值变化与1983年山东菏泽Ms 5.9地震和1985年河北任县Ms5.0地震的关系。结果显示，在这两次中强地震前分别有明显的减熵异常过程，并且一次比一次明显，中强地震都发生在低熵值处，震后恢复到高熵值的变化过程。这可能反映了地下流体构成的信息源系统在地震孕育和发生过程中的减熵有序变化。通过研究认为，该区模糊熵值减到0.907为发震前兆异常警戒线，并且离中强地震发生的时间越近，减熵过程越大；震级越大，减熵过程越明显，减熵时间越长。 相似文献
20.
通过对距离和震级的分档将权重引入两步回归法: 第一步, 将地震记录按距离分档, 每个记录得到的权重为w'ij=1/(njni)(其中nj为该记录所在档的地震数, ni为该记录的地震在此档中的记录数), 这种权重的取法不仅使各档的权重相同, 而且保证每档中不同地震在各档中的权重也相同; 第二步, 将地震按震级分档, 每次地震得到的权重为v'k=1/nk(其中nk为该地震所在档的地震数). 以Joyner 和Boore的数据为分析对象进行加权两步法的回归, 并与传统两步法回归的结果进行比较. 结果表明: 传统两步法在近场拟合的小震峰值加速度的估计值偏大, 大震峰值加速度的估计值偏小, 其衰减曲线在远场的衰减速度过快; 而加权两步法则能更好地反映地震动的空间分布规律. 相似文献