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1.
Ｔｈｅｒｅｌａｔｉｏｎｓｈｉｐｓｂｅｔｗｅｎｅａｒｔｈｑｕａｋｅｓａｎｄｐｏｓｉｔｉｏｎｓｏｆｔｈｅｓｕｎａｎｄｍｏｏｎ（Ⅱ）——Ｓｏｍｅｔｅｍｐｏｒａｌｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｔｈｅａｆｔｅｒｓｈｏｃｋｓｅｑｕｅｎｃｅｓｏｆｓｔｒｏｎｇｅ... 相似文献
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研究我国东部9次余震序列的总体特征得到:余震频度符合 n=n1t-h关系;频度和强度随时间衰减较慢;最大地震后3、4天内发生的余震所勾划的余震区常常比最终余震区小;多数余震分布在地壳中5至10公里的深度上.一些强余震前的中小余震时空分布有下述特征:（1）强余震前几天至十几天,余震序列的频度偏离正常衰减值;（2）强余震前有中小余震震中向下一次强余震的震中附近扩展或形成空区的现象;（3）强余震前震级序列出现缺震现象;（4）余震序列有准周期性.上述特性预示其后将发生强余震,同时表明强余震有类似于大地震的孕震过程.种种现象还表明余震序列在时间和空间上可能是由主震的直接余震和强余震的次级余震相互叠加所组成的.最后将某些特性和岩石试验结果进行了比较和讨论. 相似文献
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In this paper, we present a model for studying aftershock sequences that integrates Coulomb static stress change analysis, seismicity equations based on rate-state friction nucleation of earthquakes, slip of geometrically complex faults, and fractal-like, spatially heterogeneous models of crustal stress. In addition to modeling instantaneous aftershock seismicity rate patterns with initial clustering on the Coulomb stress increase areas and an approximately 1/t diffusion back to the pre-mainshock background seismicity, the simulations capture previously unmodeled effects. These include production of a significant number of aftershocks in the traditional Coulomb stress shadow zones and temporal changes in aftershock focal mechanism statistics. The occurrence of aftershock stress shadow zones arises from two sources. The first source is spatially heterogeneous initial crustal stress, and the second is slip on geometrically rough faults, which produces localized positive Coulomb stress changes within the traditional stress shadow zones. Temporal changes in simulated aftershock focal mechanisms result in inferred stress rotations that greatly exceed the true stress rotations due to the main shock, even for a moderately strong crust (mean stress 50 MPa) when stress is spatially heterogeneous. This arises from biased sampling of the crustal stress by the synthetic aftershocks due to the non-linear dependence of seismicity rates on stress changes. The model indicates that one cannot use focal mechanism inversion rotations to conclusively demonstrate low crustal strength (≤10 MPa); therefore, studies of crustal strength following a stress perturbation may significantly underestimate the mean crustal stress state for regions with spatially heterogeneous stress. 相似文献
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对大地震发生后强余震的震源机制,基于主要地震断层上小余震的时空分布进行了详细研究.近期在中国境内发生的强烈板内地震,如1976年唐山、1975年海城、1976年盐源——宁蒗等地震曾被中国地震台网很好记录.主震刚发生后的小余震以及强余震前后的小余震的震源用 S——P 时间的收敛法进行测定.强余震的断层是依靠这些小余震的震中分布来描绘的.可以看出有三种情况.第一,在主震断层区内,一次强余震发生在较小余震的比较不密集的部位;第二,一次强余震沿断层发生并与主震断层是共轭的;第三,一次强余震在沿平行并离开主震断层的断层上发生.可以认为,地质条件控制着强余震的发生.作为强余震的可能前兆,则有唐山地震的一次强余震,震级为7.1.其发生前,出现一些前震以及在接近主震断层方向上的某些地震台所记录的初动方向有变化.可以设想,这里的应力场在强余震发生前是有所变化的. 相似文献
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分析了发生在新疆、甘肃、青海和宁夏地区的部分中强地震的多种地震波参数（Ｐ↑－波初动符号、初动半周期、振幅比、尾波持续时间比、尾波衰减系数α值和品质因子Ｑ值）在主震后一个月内的变化情况。结果表明，强余震发生之前，余震序列的地震波参数有较明显的变化。利用这种变化，可以预报后续强余震的发生。 相似文献
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K. Nishigami 《Pure and Applied Geophysics》2006,163(2-3):601-616
The 2004 Mid Niigata Prefecture earthquake (MJMA 6.8) and its aftershock sequences generated complicated, i.e., several conjugate fault planes in their source region. In
order to understand the generating process of these earthquakes, we estimated a 3-D distribution of relative scattering coefficients
in the source region. The large slip area during the main shock rupture seems to be bounded by strong heterogeneous zones
with larger scattering coefficients. Hypocenters of the main shock and major large aftershocks with M 5-6 classes tend to be located close to stronger scattering areas. We found that one of these strong heterogeneities already
existed before the occurrence of the M 5.9 aftershock on November 8. We suppose that heterogeneous structures in the source region of this earthquake sequence affected
the initiation and growth of ruptures of the main shock and major large aftershocks. 相似文献
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Temporal features of the aftershock activities following twelve moderate shallow earthquakes in Greece have been studied quantitatively, by making use of the modified Omori's formula and Akaike's Information Criterion (AIC).Although the earthquake sequences occurred in different seismotectonic regions in Greece, similar seismic patterns before the occurrence of large aftershocks have been observed. Aftershock activity shows an appreciable decrease from the level expected from the modified Omori formula before the occurrence of the large aftershock. Also in some cases, the aftershock activity recovers to a normal level or increases beyond it prior to the occurrence of the large aftershock, if the aftershock activity is monitored immediately after the occurrence of the main shock. In such case, the observed pattern may be useful in predicting a large aftershock. 相似文献
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This paper mainly discusses the correlations of the occurrence time of the generalized preshock sequence earthquakes and the lunar and solar local hour angles over a period of time in the seismogenic zone of strong earthquake prior to a mainshock. Their group characteristics indicate that the occurrence time of earthquakes above a certain scale is modulated by the lunar and solar local hour angles. Statistical results show that the significant correlations exist between these two things, which is of some physical significance. At the same time, the differences of actions of the Sun and Moon are analyzed and the possible active mechanism is discussed from the point of earthquake-restrained as well. 相似文献
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The aftershock processes that occurred in 1990?C2008 on the Kamchatka Peninsula and in the adjacent water area are numerically modeled with the aim of forecasting the aftershock activity. The aftershocks are identified by the Molchan-Dmitrieva algorithm followed by the analysis of spatiotemporal distribution of the earthquakes, which gives the final aftershock sequences. The simulations are based on the relaxation and triggering models of the aftershock processes. The studied models adequately describe and reliably simulate the temporal behavior of the aftershock sequences. An attempt is made to forecast the aftershock processes in Kamchatka using the ETAS model. It is shown that forecasting based on the data observed during the preceding time intervals is quite accurate. This approach can be applied in the centers of seismological monitoring for estimating the aftershock activity within the first days after a strong earthquake. 相似文献
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The aftershock processes that occurred in 1990–2008 on the Kamchatka Peninsula and in the adjacent water area are numerically modeled with the aim of forecasting the aftershock activity. The aftershocks are identified by the Molchan-Dmitrieva algorithm followed by the analysis of spatiotemporal distribution of the earthquakes, which gives the final aftershock sequences. The simulations are based on the relaxation and triggering models of the aftershock processes. The studied models adequately describe and reliably simulate the temporal behavior of the aftershock sequences. An attempt is made to forecast the aftershock processes in Kamchatka using the ETAS model. It is shown that forecasting based on the data observed during the preceding time intervals is quite accurate. This approach can be applied in the centers of seismological monitoring for estimating the aftershock activity within the first days after a strong earthquake.
相似文献12.
本文研究了近几年来我国发生的一系列强地震以及部分中强地震后,短时间内余震活动的时空分布特征.结果表明,不同类型的地震序列,在大震后短时间内余震频度衰减和余震区的变化过程上有明显差别.作者认为,这种差别有可能作为一次强地震后及时对地震类型和趋势进行判断的依据之一. 相似文献
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A. I. Lutikov 《Izvestiya Physics of the Solid Earth》2008,44(3):181-192
A rational choice of the scalar seismic moment and ordering index is proposed that can be advantageously used for the monitoring of source zones of strong earthquakes in order to predict the development of a seismic situation. These parameters are the main characteristics of seismotectonic deformation. The ordering index characterizes a regular change in time of chaotization and ordering phases of the seismic process related to the occurrence of strong aftershocks. Using the December 5, 1997, Kronotskii (M w = 7.8) and December 26, 2004, Sumatra (M w = 9.0) earthquakes as an example, temporal variations of the studies parameters in the aftershock zones of these earthquakes are analyzed in detail. 相似文献
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中强地震余震序列地震目录编目是否完备、 震源参数是否准确,直接影响余震序列特征分析、 震后趋势快速判断和强余震预测等研究结果的科学性和可靠性. 2013年7月22日甘肃岷县-漳县MS6.6地震余震序列目录中存在较多单台记录地震事件,地震观测报告仅给出其震级,而未给出震中位置. 由于余震波形间的相互交叠干扰,使得余震最大振幅的测量误差较大,造成地震观测报告给出的单台事件震级误差较大. 精确估计单台记录地震事件的震中和震级,能够补充完善现有地震目录,提高地震目录的完备性. 本文对单台记录地震事件震中和震级的估计不仅限于单个台站,而是通过分析区域台网中多个台站的波形记录实现. 首先以余震序列中震级较大、 波形记录信噪比较高的地震波形作为模板,使用波形互相关震相检测技术,检测单台记录的地震事件在多个台站的震相到时. 如果能在4个以上台站检测到震相,则利用测震台网常用的HYPOSAT方法估计其震中位置,并利用多个台站记录波形与模板地震的振幅比估计其震级. 之后计算主震发生后不同时间的最小完备性震级,并通过线性拟合得到最小完备性震级随时间变化的表达式,以分析此地震余震序列的目录完备性. 经过计算共得到253个单台记录地震事件的震级和其中177个事件的震中位置,其震中空间分布范围与余震序列中其它地震分布范围基本一致. 震级复测以及与人工拾取震相到时误差对比表明,该方法所得震相检测和震级估计结果具有较好的可靠性. 主震及最大余震发生后的短时间内,有较多数量单台事件的目录所给出的震级偏低,分析认为可能受主震与较大余震后续震相以及余震间相互干扰所致. 主震发生0.02—0.3天内,其余震序列最小完备性震级随时间的对数呈线性下降,在0.3天后最小完备性震级稳定在ML1.1左右. 相似文献
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Data replenishment of five moderate earthquake sequences in Japan,with semi-automatic cluster selection 
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下载免费PDF全文 Missing early aftershocks following relatively large or moderate earthquakes can cause significant bias in the analysis of seismic catalogs. In this paper, we systematically address the aftershock missing problem for five earthquake sequences associated with moderate-size events that occurred inland Japan, by using a stochastic replenishing method. The method is based on the notion that if a point process (e.g., earthquake sequence) with time-independent marks (e.g., magnitudes) is completely observed, it can be transformed into a homogeneous Poisson process by a bi-scale empirical transformation. We use the Japan Meteorological Agency (JMA) earthquake catalog to select the aftershock data and replenish the missing early events using the later complete part of each aftershock sequence. The time windows for each sequence span from 6 months before the mainshock to three months after. The semi-automatic spatial selection uses a clustering method for the epicentral selection of earthquakes. The results obtained for the original JMA catalog and replenished datasets are compared to get insight into the biases that the missing early aftershocks may cause on the Omori-Utsu law parameters’ estimation, characterizing the aftershock decay with time from the mainshock. We have also compared the Omori-Utsu law parameter estimates for two datasets following the same mainshock; the first dataset is the replenished sequence, while the second dataset has been obtained by waveform-based analysis to detect early aftershocks that are not recorded in the JMA catalog. Our results demonstrate that the Omori-Utsu law parameters estimated for the replenished datasets are robust with respect to the threshold magnitude used for the analyzed datasets. Even when using aftershock time windows as short as three days, the replenished datasets provide stable Omori-Utsu law parameter estimations. The p-values for all the analyzed sequences are about 1.1 and c-values are significantly smaller compared to those of original datasets. Our findings prove that the replenishment method is a fast, reliable approach to address the missing aftershock problem. 相似文献
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1990年4月17日乌恰6.4级地震序列有以下特征:(1)主震型序列;(2)强余震前小地震震中向强余震的震中附近迁移;(3)余震频度衰减快;(4)余震在主震和最大余震之间活动;(5)较大余震存在“密集-平静-发震”的规律;(6)存在晚期较强余震。 相似文献
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R. N. Vakarchuk R. E. Tatevossian Zh. Ya. Aptekman V. V. Bykova 《Izvestiya Physics of the Solid Earth》2013,49(5):653-659
The source of the 1991 Racha earthquake in the Greater Caucasus generally corresponds to thrusting, which is characteristic of the predominant regional compression stress field. A more adequate view of the rupture process is provided by a complex source model composed of three subsources. This model is reconstructed by the body-wave inversion and consistent with the spatial distribution of the aftershocks. In terms of the suggested model, at the last stage of the rupture process, the opposite slip type (normal faulting) is observed in the source, which seems to be objective. It compensates the rapid (probably short) local redistribution of stresses caused by the thrusts in the first two subsources. The surface deformations observed in the epicentral zones of strong earthquakes are probably the analogs of such a compensative mechanism. For example, in the rear parts of the thrusts associated with the surface ruptures, normal faults trending parallel to the strike of the thrust line occur. Another analog of the compensative motion is probably the peculiarities of the aftershock sources. It has long since been noted (Kuznetsova et al., 1976) that some fault plane solutions in the aftershock sequences of strong earthquakes are close to the main shock solution, while others are different. The explanation of this phenomenon is suggested in (Kuznetsova et al., 1976; Kostrov and Das, 1988). In (Kuznetsova et al., 1976), these events are referred to as the aftershocks due to the fracture growth and aftershocks of relaxation, respectively. 相似文献
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Forecasting aftershock activity: 1. Adaptive estimates based on the Omori and Gutenberg–Richter laws
The method for forecasting the intensity of the aftershock processes after strong earthquakes in different magnitude intervals is considered. The method is based on the joint use of the time model of the aftershock process and the Gutenberg–Richter law. The time model serves for estimating the intensity of the aftershock flow with a magnitude larger than or equal to the magnitude of completeness. The Gutenberg–Richter law is used for magnitude scaling. The suggested approach implements successive refinement of the parameters of both components of the method, which is the main novelty distinguishing it from the previous ones. This approach, to a significant extent, takes into account the variations in the parameters of the frequency–magnitude distribution, which often show themselves by the decreasing fraction of stronger aftershocks with time. Testing the method on eight aftershock sequences in the regions with different patterns of seismicity demonstrates the high probability of successful forecasts. The suggested technique can be employed in seismological monitoring centers for forecasting the aftershock activity of a strong earthquake based on the results of operational processing. 相似文献
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基于区域地震活动频次对比的余震删除方法 总被引：2，自引：0，他引：2
从尽可能科学地删除余震, 又保留有价值的地震预测信息的目的出发, 提出了一种既考虑地震序列特征, 又基于主震后孕震区内的余震活动频次与区域地震活动正常时段频次相比的删除余震方法(简称SMRZ方法), 编制了相应的计算程序。 以西北地区发生的几次较大地震为例, 对该文提出的SMRZ方法、 广泛使用的K-K方法以及G-C方法的删除余震效果进行了对比研究。 结果表明, 与其他方法相比, 笔者提出的方法识别余震时、 空分布范围比较合理, 同时保留了对未来地震有重要预测意义的前震, 有较好的实际应用效果。 相似文献