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本文应用数学门限自回归模型和样条函数,研究了甘肃东南部的地震活动特征。结论如下:(1)甘肃东南部的地震活动具有"准周期"现象,本世纪以来已经历了三个"准周期",目前,处于第三活动期。(2)1900年以来的地震活动处于较低的水平,大多数地震的震级为5-6级。根据本文的研究,下一次地震的震级约为5级左右,目前发震的概率为0.74.(3)震级大于4.7级地震的空间分布图象与数字模拟实验结果一致。 相似文献
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采用"自激励门限自回归模型"(SETAR)对山西、河北平原带及郯庐带1970年以来半年度最高震级序列进行了分析计算,给出了1998年以来山西、河北平原带及郯庐带半年度最高预测震级。结果表明,该模型对半年度地震趋势预测具有良好的预测效果,这种建模方法有效,模型可信。 相似文献
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传统利用灰色关联分析方法对地震波动强度变化进行数学建模分析与仿真时,对地震波动强度变化的数列进行仿真分析时,忽略了地震波动强度的时间属性对结果的影响,导致分析结果准确性较低。本论述提出新的地震波动强度变化数学建模分析与仿真方法,通过地震波动强度序列的经验分布确定门限自回归模型的门限值,依据该门限值、AIC最小准则以及最小残差平方等方法获取地震波动强度序列的门限自回归模型,分析自回归模型的极限环和振荡的属性特点,得到地震波动强度变化的初步数值模拟结果。本论述构建了基于均生函数的地震波动强度序列的数学模型,通过均生函数数学建模方法拟合地震波动强度时间序列,依据时间序列基于双评分准则选取拟合周期,实现地震波动强度的数值仿真。实验结果表明,所提方法对地震波动强度变化模型具有较高的准确性和稳定性。 相似文献
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新疆近期两次地震序列的时间信息维特征 总被引：1，自引：0，他引：1
蒋海昆 《地震地磁观测与研究》1992,13(2):1-7
本文以新疆两次中强地震的余震序列为例,探讨地震序列不均勻时间分布的分形特征。对其信息维的测算表明,无标度区范围基本稳定,同一时间段内信息维数随震级下限的升高略有降低;而对相同震级下限的样本群而言,不同时段的信息维数具有一定的差异。通常是强余震活动结束之后的信息维数略高于强余震活动期间的信息维数。这一特点对大震后地震趋势的合理估计具有积极意义。 相似文献
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极值理论在地震危险性分析中有着重要应用, 发震震级超过某一阈值的超出量分布可以近似为广义帕累托分布. 基于广义帕累托分布给出了若干地震活动性参数的估计公式, 包括强震震级分布、 地震复发周期和重现水平、 期望重现震级、 地震危险性概率和潜在震级上限等; 以云南地区震级资料为基础数据, 讨论了阈值选取、 模型拟合诊断和参数估计; 在此基础上计算了该地区的地震活动性参数. 结果表明, 广义帕累托分布较好地刻画了强震震级分布, 通过超阈值(POT)模型计算的复发周期与实际复发间隔统计基本一致, 高分位数估计在一定阈值范围内表现稳定, 为工程抗震中潜在震级上限的确定提供了一种途径. 相似文献
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叙述门限自回归模型建模的基本原理及步骤,利用东北地区年最大震级序列数据建立门限自同归模型SETAR(2,4,3),并依此对东北地区未来可能发生的最大地震进行预测.结果表明,该模型预测精度较高,其研究结论对东北地区未来地震活动趋势预测具有参考意义. 相似文献
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基于广义帕累托分布构建地震活动性模型,因其输入参数取值难以避免不确定性,导致依据该模型所得的地震危险性估计结果具有不确定性。鉴于此,本文选取青藏高原东北缘为研究区,提出了基于全域敏感性分析的地震危险性估计的不确定性分析流程和方法。首先,利用地震活动性广义帕累托模型,进行研究区地震危险性估计;然后,选取地震记录的起始时间和震级阈值作为地震活动性模型的输入参数,采用具有全域敏感性分析功能的E-FAST方法,对上述两个参数的不确定性以及两参数之间的相互作用对地震危险性估计不确定性的影响进行定量分析。结果表明:地震危险性估计结果（不同重现期的震级重现水平、震级上限及相应的置信区间）对两个输入参数中的震级阈值更为敏感;不同重现期的地震危险性估计结果对震级阈值的敏感程度不同;对不同的重现期而言,在影响地震危险性估计结果的不确定性上,两个输入参数之间存在非线性效应,且非线性效应程度不同。本文提出的不确定性分析流程和方法,可以推广应用于基于其它类型地震活动性模型的地震危险性估计不确定性分析。 相似文献
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极值统计是研究较少发生但一旦发生即产生极大影响的随机事件的有效方法。本文以地震活动频繁的昆仑山地区作为研究区域,建立了基于广义帕累托分布的超阈值（POT）模型,并讨论了该地区若干地震活动性参数,包括强震震级分布、潜在震级上限、强震平均复发间隔、一定周期内的强震发震概率、一定时期内的重现水平和超定值重现震级。经统计分析得到:该地区震级阈值选定为MS5.5,超阈值期望震级为MS6.81,潜在震级上限高达MS9.08,MS8.0的平均复发间隔仅为66.8年,未来3年该地区发生MS5.5～MS6.5的概率在80%以上,百年重现水平即可达到历史最大震级MS8.1。 相似文献
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地震时间分布特征研究是进行地震预测和地震危险性分析的重要基础。以中国海域统一地震目录为基础资料，以指数分布模型、伽马分布模型、威布尔分布模型、对数正态分布模型以及布朗过程时间分布（BPT）模型为目标模型，采用极大似然法估算模型参数。根据赤池信息准则（AIC）、贝叶斯信息准则（BIC）以及K-S检验结果确定能够描述海域地震时间分布的最优模型。结果表明，对于震级相对较小（ M <6）的地震，指数分布、伽马分布以及威布尔分布均能较好地描述其时间分布特征；在大的区域范围内（如整个海域），震级相对较大（ M >6）的地震可完全采用指数分布描述其时间分布特征；在较小的区域范围内（如地震带），大地震时间间隔可能更加符合对数正态分布和BPT分布。此外，文中还采用扩散熵分析法研究地震之间的丛集性和时间相关性，结果表明，地震活动存在长期记忆性，震级相对较小（ M <6）的地震受更大地震的影响，从而在时间上表现出丛集特征。本文的研究结果对地震预测、地震危险性计算中地震时间分布模型选择和地震活动性参数计算具有一定参考价值，对理解地震孕育发生机理具有一定科学意义。 相似文献
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THE APPLICATION OF PETROLEUM SEISMIC DATA TO THE BURIED ACTIVE FAULT DETECTION——A CASE STUDY OF ACTIVE FAULTS SURVEYING IN SONGYUAN CITY 
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下载免费PDF全文 Located in the south of the Songliao Basin, Songyuan City is one of the few high seismic intensity regions (Ⅷ degree regions) in Northeast China, where a magnitude 6(3/4) earthquake took place in 1119. Since 2013, many earthquakes of magnitude above 5 have occurred in Chaganhua Town which is 100km southwest of Songyuan. The faults in the study region are almost all in a concealed state and covered by the Quaternary system, therefore, geophysical investigation, drilling and other similar means are required to determine their distribution, occurrence, nature and active period. Many seismic explorations in this region aiming at surveying the oil bearing structure have been conducted by Jilin Oilfield, which provides detailed seismic exploration information for preliminary detection of active faults. In this paper, the main features of petroleum-related seismic data and major methods for extracting tectonic information are presented; on the plain, the trace information of the main structure is extracted by the t0 interface contour map which allows direct reflection of rises and falls of stratal interfaces and the tectonic characteristics of the corresponding geologic period; on the section, the "extending upwards" characteristics of faults are captured by tracing and marking geological phenomena in the reflective standard layer, faults, the surface of unconformity and so on. Under the comprehensive use of the "3D" structure in the interpretation of the results, accurate spatial distribution information of main faults are obtained in the study region, this offers an effective approach to preliminary judgment of the activity of faults in this region. Meanwhile, the active age of the target faults is identified by superimposing the deep and shallow seismic data and integrating with the drilling detection. 相似文献
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Antonio Rovelli 《Physics of the Earth and Planetary Interiors》1983,33(2):94-110
Stochastic modelling is applied to the analysis of local earthquake recordings, which are usually extremely rich in random incident-wave trains that are chaotically superimposed because of scattering effects in the Earth's crust. The presence in the seismic signal of effects connected with the scale of inhomogeneity in the lithosphere cannot be deterministically described in detail. The application of a stochastic second-order autoregressive model to accelerometric records for the higher magnitude (ML ? 6) Friuli earthquakes and to short-period seismometric records for the aftershocks of the strong earthquake of 6 May 1976 has allowed inferences to be drawn about the spectral properties of seismic signals and the propagation mechanisms of seismic waves. These inferences are based on an extremely small number of parameters of a mathematical model suitable for simultaneously describing the random sequence of scattered wave trains in the time and frequency domains. Useful physical information has been obtained about the dynamic characteristic correlation times and the predominant frequency of the seismic signals; moreover, the strength, σ2e(t), of the innovation of the stochastic process fitting the real digital data set has been estimated. From the envelopes of σ2e(t), the quantity heuristically used in the stochastic approach to describe seismic excitation, the·mean free-path between successive scatterings (l), or the equivalent diffusivity coefficient (d) and turbidity (g), and their dependence on seismic wave frequency have been investigated. For Friuli, using seismometric data at an epicentral distance of ～ 20 km and earthquakes with a magnitude just under 2, mean free-path estimates obtained by means of autoregressive parameters vary from ～ 5 km for the strong interaction model to ～ 30 km for the single scattering model. Furthermore, by means of accelerometric records for the strongest earthquakes in Friuli during May and September 1976, the dependence for the maximum of the seismic excitation on the epicentral distance R was estimated as (σ2e)max ～ R?ν (with ν 1.94 ± 0.13), which is in good agreement with results obtained for the same region using standard methods by means of acceleration peaks versus R. Lastly, stochastic modelling provides a method of estimating change versus time for the predominant frequency and characteristic correlation time of narrow band digital recordings. These two parameters were computed by means of autoregressive parameters in different physical situations and were found to be functions of the earthquake source, the instrumentation frequency response, and the Earth's filtering effects. 相似文献
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基于POCS方法指数阈值模型的不规则地震数据重建(英文) 总被引：8，自引：3，他引：5
不规则地震数据会对地震多道处理技术的正确运行造成不良影响,降低地震资料的处理质量。本文将广泛用于图形图像重建的凸集投影方法应用到地震数据重建领域,实现规则样不规则道缺失数据的插值重建。对于整道缺失地震数据,将POCS迭代重建过程由时间域转移到频率域实现,避免每次迭代都对时间做正反Fourier变换,节约了计算量。在迭代过程中,阈值参数的选择方式对重建效率有重要影响。本文设计了两种阈值集合模型进行重建试验,试验结果表明:在相同重建效果下,指数型阈值集合模型可以有效减少迭代次数,提高重建效率。此外,分析了POCS重建方法的抗噪性能和抗假频性能。最后,理论模型和实际资料处理效果验证了本文重建方法的正确性和有效性。 相似文献
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This paper proposes a simple class of threshold autoregressive model for purpose of forecasting daily maximum ozone concentrations
in Southern California. Linear time series model has been widely considered in environmental modeling. However, this class
of models fails to capture the nonlinearity in ozone process and the complexity of meteorological interactions with ozone.
In this article, we used the threshold autoregressive models with two classes of regimes; periodic and meteorological regimes.
Days in week were used for the periodic regimes and the regression tree method was used to define the regimes as a function
of meteorological variables. As the reference model we used the autoregressive model with lagged ozone and various lagged
meteorological variables as the covariates. The proposed models were applied to a 3-year dataset of daily maximum ozone concentrations
obtained from five monitoring stations in San Bernardino County, CA and their forecast performances were evaluated using an
independent year-long dataset from the same stations. The results showed that the threshold models well capture the nonlinearity
in ozone process and remove the nonstationarity in model residuals. The threshold models outperformed the non-threshold autoregressive
models in day-ahead forecasts. The tree-based model showed slightly better performance than the periodic threshold model. 相似文献
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Janez K. Lapajne Barbara Sket Motnikar Blaz Zabukovec Polona Zupancic 《Journal of Seismology》1997,1(1):73-85
A progress report on the mapping effort for construction of a peak ground acceleration (PGA) map of Slovenia for 475-year return period for rock and firm soil is presented. The methodology is similar to that recently applied in Central and Eastern United States. It is based on historical seismicity spatially smoothed to different length scales. The procedure is described by Frankel (1995). He uses the characteristic earthquake recurrence relationship and in his firt version four different seismicity models. We also use four seismicity models. But instead of characteristic earthquake recurrence, we use the doubly truncated exponential magnitude-frequency relationship; no evidence of characteristic earthquakes in Slovenia has been found yet. Three of our models are similar to Frankel's first three models. Model 1 uses spatially smoothed activity rate based on magnitude 3.7 and above events since 1880. Model 2 deals with spatially smoothed activity rate based on magnitude 5.0 abd above events since 1690. Model 3 smoothes the observed activity over the entire region; it represents a uniform seismicity zone. Frankel skipped this model in his latest version (Frankel et al. 1996). In model 4, we introduce a new approach of calculating seismic activity rate taking into account released seismic energy. The ground motion attenuation model of Pugliese and Sabetta (1989) is used for all models. PGA maps for models 1, 2, 3 and 4 have been calculated, and a weighted mean map derived from them. A map of model 1 has been compared with the corresponding source zone map; the two maps do not differ significantly. A worst-case map derived from all four models has also been produced. 相似文献
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东汉早期(公元25—127年)的地震史料十分宝贵, 它反映了从远古零散、 不系统的地震记载转入连续记载并逐渐认识地震的过程. 这时的地震事件较多, 但研究不充分, 地震参数基本呈空白状. 史料的记载方式以“郡国地震”和“京师地震”为主; 时间上, 基本在汉和帝以后; 地点上, 以大华北为主. 本文具体分析了东汉早期的33次地震事件, 利用新的地震烈度衰减关系, 采用郡国平均地理面积和有感面积的概念, 比照地震范例的标准, 按《中国地震目录》的烈度震级表进行参数估算. 研究期间最主要的地震事件是4次震级≥6 1/2 的强震, 即公元46年10月和119年3月南阳地震、 121年10月冀南-鲁西地震和123年5月汉阳地震, 震后都有持续1—2年的余震活动. 公元118年前的地震主要分布于大华北, 震中至京师洛阳的距离多在200 km以外. 除两次5 1/2 —6级地震外, 均属5—5 1/2 级中等强度地震, 少数小于4 3/4 级. 京师洛阳虽经历过多次地震, 但其受影响程度并不强, 基本为有感或强有感的水平, 没有遭受过破坏性或中等强度的震害. 相似文献