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基于积函数极值法,确定了刚度分布未知的挡水坝的地震剪力和地震弯矩上限。计算表明,西方的理论解与文献「１」,「２」的数值计算结果是一致的。 相似文献
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目前,工程结构抗震设计已经发展到以极限状态概率为安全标准的概率设计阶段。极值统计方法所得结果可以提供工程结构抗震设计参数。本文用极值统计分析方法研究了工程场地历史地震影响烈度的分布特征,探讨了利用历史地震影响评价工程场地地震危险性的可能性。结果表明,在历史地震资料比较丰富的地区,可以采用极值统计分析方法,从工程场地影响烈度时间序列中取得抗震设计的依据。在具体分析中,宜采用陈培善改进后的极值分布函数(Gc)和=(l——0.44)/(n+0.12)数据点拟合方式。 相似文献
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利用陈培善等人对极值理论修改后的极值分布函数模型对1971-01～2012-06台湾地区的地震资料进行统计分析。根据地震活动和地震地质构造特征划分区域、确定边界,单位时间的选取由其地震发生的频度和能量来确定,单位时间内最小与最大地震的确定分别考虑相关区域内台网的监控能力以及删除余震后的实际情况,根据修正后的极值理论统计计算出相应地震的复发周期及在未来一定时间内可能发生相应地震的次数与发震概率,并对有关结果进行模型检验和映震能力分析,同时与利用M-T图及震级与G-R关系获取的M≥7.0级地震的复发周期进行比较。 相似文献
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本文应用极值分布函数和震级平均复发周期概念,研究了华南5条地震带的缺震情况,外推未来5至10年结果表明:右江带无M≥5级地震:东南沿海内带有5.6～5.9级地震危险,但危险性不大;东南沿海外带发生6.5～6.9级地震的概率达69％;台湾西带随时可能发生5级和6级地震;台湾东带随时有可能发生6级和7级地震。 相似文献
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R. B. S. Yadav Yusuf Bayrak J. N. Tripathi S. Chopra A. P. Singh Erdem Bayrak 《Pure and Applied Geophysics》2012,169(9):1619-1639
The maximum likelihood estimation method is applied to study the geographical distribution of earthquake hazard parameters and seismicity in 28 seismogenic source zones of NW Himalaya and the adjoining regions. For this purpose, we have prepared a reliable, homogeneous and complete earthquake catalogue during the period 1500–2010. The technique used here allows the data to contain either historical or instrumental era or even a combination of the both. In this study, the earthquake hazard parameters, which include maximum regional magnitude (M max), mean seismic activity rate (λ), the parameter b (or β?=?b/log e) of Gutenberg–Richter (G–R) frequency-magnitude relationship, the return periods of earthquakes with a certain threshold magnitude along with their probabilities of occurrences have been calculated using only instrumental earthquake data during the period 1900–2010. The uncertainties in magnitude have been also taken into consideration during the calculation of hazard parameters. The earthquake hazard in the whole NW Himalaya region has been calculated in 28 seismogenic source zones delineated on the basis of seismicity level, tectonics and focal mechanism. The annual probability of exceedance of earthquake (activity rate) of certain magnitude is also calculated for all seismogenic source zones. The obtained earthquake hazard parameters were geographically distributed in all 28 seismogenic source zones to analyze the spatial variation of localized seismicity parameters. It is observed that seismic hazard level is high in Quetta-Kirthar-Sulaiman region in Pakistan, Hindukush-Pamir Himalaya region and Uttarkashi-Chamoli region in Himalayan Frontal Thrust belt. The source zones that are expected to have maximum regional magnitude (M max) of more than 8.0 are Quetta, southern Pamir, Caucasus and Kashmir-Himanchal Pradesh which have experienced such magnitude of earthquakes in the past. It is observed that seismic hazard level varies spatially from one zone to another which suggests that the examined regions have high crustal heterogeneity and seismotectonic complexity. 相似文献
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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
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东昆仑断裂带是青藏高原东北部一条重要的活动断裂, 构成了巴颜喀拉块体的北边界。 根据阿尼玛卿山两侧滑动速率和历史地震的差异, 将断裂带分为东西两个部分。 滑动速率由西向东递减, 近百年的历史地震产生的破裂基本覆盖了西部和东部的一部分。 随着巴颜喀拉块体周缘强震的持续发生, 作为块体北边界的东昆仑断裂带的地震空区及地震潜势研究变得更加重要。 近些年通过对东昆仑断裂带不同段的研究得到了较多的滑动速率和古地震序列数据, 为评价断裂带未来百年地震危险性提供了有利条件。 利用NB模型中的对数正态分布方法, 得到了东昆仑断裂带在未来100 a的发震概率, 研究表明, 东部(玛曲段)发震概率相对较高, 需要进一步关注。 相似文献
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通过与更早地震资料的对比, 研究了鲜水河断裂带, 川滇地壳块体东带、 西带, 松潘、 龙门山断裂带以及整个川滇地区较长时间尺度的地震活动盛衰交替性。 结果表明, 川滇东带北段(鲜水河断裂带)、 松潘、 龙门山地震带及川滇西带中段和南段(主要是红河断裂带)的地震活动具有明显的几十到百年尺度的盛衰交替性。 而川滇东带中南段(安宁河-则木河-小江断裂带)与川滇西带北段(金沙江断裂带)在上述地震带的平静期里, 中强以上地震频次明显减少, 但有个别7级以上强震发生。 这样, 整个川滇地区地震活动的盛衰交替性呈现一种比较复杂的阶段性特征: 伴随频繁中强震的强震活跃期与突发强震活动期交替出现。 值得注意的是, 川滇地区从19世纪末开始的伴随频繁中强震的强震活跃期已超过百年, 目前出现长期平静, 应注意进入突发强震活动期的可能性。 根据川滇地区上一个突发强震活动期突发强震的空间分布, 推测未来的突发强震可能发生在南北向断裂带, 或其他方向断裂带与南北向断裂带的交汇部。 文中还对上述统计现象的机理作了简要讨论。 相似文献
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Ram Bichar Singh Yadav Jayant Nath Tripathi Bal Krishna Rastogi Mridul Chandra Das Sumer Chopra 《Pure and Applied Geophysics》2010,167(11):1331-1342
Northeast India and adjoining regions (20°–32° N and 87°–100° E) are highly vulnerable to earthquake hazard in the Indian
sub-continent, which fall under seismic zones V, IV and III in the seismic zoning map of India with magnitudes M exceeding 8, 7 and 6, respectively. It has experienced two devastating earthquakes, namely, the Shillong Plateau earthquake
of June 12, 1897 (M
w
8.1) and the Assam earthquake of August 15, 1950 (M
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8.5) that caused huge loss of lives and property in the Indian sub-continent. In the present study, the probabilities of
the occurrences of earthquakes with magnitude M ≥ 7.0 during a specified interval of time has been estimated on the basis of three probabilistic models, namely, Weibull,
Gamma and Lognormal, with the help of the earthquake catalogue spanning the period 1846 to 1995. The method of maximum likelihood
has been used to estimate the earthquake hazard parameters. The logarithmic probability of likelihood function (ln L) is estimated
and used to compare the suitability of models and it was found that the Gamma model fits best with the actual data. The sample
mean interval of occurrence of such earthquakes is estimated as 7.82 years in the northeast India region and the expected
mean values for Weibull, Gamma and Lognormal distributions are estimated as 7.837, 7.820 and 8.269 years, respectively. The
estimated cumulative probability for an earthquake M ≥ 7.0 reaches 0.8 after about 15–16 (2010–2011) years and 0.9 after about 18–20 (2013–2015) years from the occurrence of
the last earthquake (1995) in the region. The estimated conditional probability also reaches 0.8 to 0.9 after about 13–17
(2008–2012) years in the considered region for an earthquake M ≥ 7.0 when the elapsed time is zero years. However, the conditional probability reaches 0.8 to 0.9 after about 9–13 (2018–2022)
years for earthquake M ≥ 7.0 when the elapsed time is 14 years (i.e. 2009). 相似文献
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研究华北地区(34-42N,108-124E)地震活动的时空分布表明,不同的时期,主要的地震活动在不同的区域发生,随时空的整体性转移是明显的.太行山前断裂带是该区最重要的构造带之一,它不仅控制了其两端的地震活动,也控制了以它为界的东、西两区的地震活动.并指出,大约从19世纪以来,华北地区的地震活动主要在东区,而不在西区,地震活动格局已经发生了重大改变;作为地震预报的重点监视区,应着重考虑目前正在活动的地区,这对地震的长期预报是重要的. 相似文献
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应用混合极值理论及最大似然法估计东南沿海各地震区的地震危险性 总被引：1，自引：0，他引：1
将东南沿海地区划分为７个地震区带，利用历史及现代地震资料，动用混合极值理论及最大似然法分析了各个地震区带的地震危险性，并采用预测检验的方法确定了各个地震区带的危险阈值，对各地震区未来两年的中小地震及未来５年的中强地震的危险性分别给出了定量估计。 相似文献
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鄂尔多斯周缘地震带地震活动的分期和相关分析 总被引：3，自引：0，他引：3
利用最优分割法对鄂尔多斯周缘地震带(区)的地震活动进行了分期,并作了相关分析。结果表明,1000年以来汾渭地震带北段可划为4个活跃期,每个活跃期的中心间距约300年,最大地震为7级,天水—陕南地震带(区)近一、二百年的地震活动可分为持续约10年左右的几个地震簇。所有分期中,海原地震带能量释放最大,且最近仍很活跃。汾渭地震带和海原—银川地震带活跃期存在相关现象,且其南段往往先于北段活跃,目前活动水平较低。该带1900年以来地震还有与河套地震带地震相呼应的现象和沿构造带南北迁移的规律。根据分期和相关结果推测,鄂尔多斯周缘各地震带都存在中强地震背景。其中海原—银川地震带近期发生5—6级或更大地震的可能性较大,天水—陕南地震带近期也有发生中强地震的可能。汾渭地震带虽然存在孕育6级以上大震的背景,但近年还不会发生强震。 相似文献
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Based on historical earthquake data, we use statistical methods to study integrated recurrence behaviors of strong earthquakes along 7 selected active fault zones in the Sichuan-Yunnan region. The results show that recurrences of strong earthquakes in the 7 fault zones display near-random, random and clustering behaviors. The recurrence processes are never quasiperiodic, and are neither strength-time nor time-strength dependent. The more independent segments for strong earthquake rupturing a fault zone has, the more complicated the corresponding recurrence process is. And relatively active periods and quiescent periods for earthquake activity occur alternatively. Within the active periods, the distribution of recurrence time intervals between earthquakes has relatively large discretion, and can be modelled well by a Weibull distribution. The time distribution of the quiescent periods has relatively small discretion, and can be approximately described by some distributions as the normal. Both the durations of the active periods and the numbers of strong earthquakes within the active periods vary obviously cycle by cycle, leading to the relatively active periods having never repeated quasi-periodically. Therefore, the probabilistic assessment for middle- and longterm seismic hazard for entireties of active fault zones based on data of historical strong earthquakes on the fault zones still faces difficulty. 相似文献