共查询到20条相似文献，搜索用时 15 毫秒
1.
本文应用断裂力学和流变介质中波的传播理论来研究震前长周期形变波的波动源以及这类波传播的一些主要特征,在理论研究结果的基础上,对我国多次较大地震前观测到的短临地震前兆进行了剖析,并从中识别出一些可能与长周期形变波有关的短临地震前兆.首先,从粘滑与破裂这两类主要地震机制出发,提出了粘滑前的预滑与破裂前断裂的预扩展(亚稳态扩展)可能是产生震前长周期波的两类波动源的看法,并着重从理论上讨论了后一类波动源.其次,以地壳流变介质模型为基础,对长周期形变波的传播特性进行了理论研究.选用地壳的广义流变介质模型,求解了所述的两类波动源在这种流变地壳介质中引起的长周期形变波传播的动力学问题,从理论上得出了长周期形变波在地壳内传播的某些一般特征.然后,专门分析了我国多次大地震前实际观测到的短期和临震地震前兆资料,并着重讨论了唐山地震的短临前兆.在这些不同类型的短临地震前兆中,我们得出地下水位、地倾斜及潮位自动记录曲线等的某些振动式及阶跃式短临地震前兆与长周期形变波的理论探讨结果基本相符,因而可以认为它们属于由长周期形变波所反映的地震前兆.在理论研究与实际资料分析的基础上,本文归纳了由长周期形变波所引起的短临地震前兆的一些基本特征,包括传播速度、衰 相似文献
2.
Seismoionospheric disturbances in the parameters of the ionospheric F 2 and sporadic E layers at the chain of the Japanese stations for vertical sounding of the ionosphere before strong crustal earthquakes with M>6.5 during the period from 1968 to 1992 have been considered. The dependence of the disturbance time of appearance in the ionospheric parameters on the earthquake magnitude and epicentral distance, obtained for each specific earthquake using the selected series of ionospheric stations, made it possible to consider these disturbances among medium-term precursors of earthquakes. The velocity of the disturbance front apparent motion has been determined based on the model of horizontal radially-isotropic disturbance propagation from the projection of the impending earthquake epicenter to the ionospheric altitudes. The conclusion has been made that the distinguished seismoionospheric disturbances follow the boundary of the earthquake preparation region, expanding on the Earth’s surface. 相似文献
3.
地震前兆检验的地球动力学问题对地震预测问题争论的评述(之三) 总被引：1，自引：1，他引：1
地震前兆的效能检验问题既是地震预测研究中的一个基本问题，也是近年来围绕地震预测问题的一个争论焦点。传统的地震预测研究中关于地震前兆机理的一个基本假定，即地震前兆来自地震孕育过程中应力场的某种变化，与传统的地震前兆检验方案，即针对“异常”信息统计与地震之间的“对应”情况，并进行统计显著性检验，存在一个内在的逻辑矛盾。地震前兆的检验不是一个简单的统计问题，而是一个地球动力学问题，不考虑地球动力学的地震前兆检验是没有意义的，由此得到的检验结果则可能对相关研究造成误导。 相似文献
4.
以震中迁移始发点的前兆讨论了唐山7.8级地震震中位置的预测,并以此为例分析了汶川8级地震和芦山7级地震的前兆问题。另外,从震中迁移延长线上的前兆来讨论了唐山大震的发生时间。 相似文献
5.
地震强地面运动预测对工程的抗震设计,地震危害性分析以及减轻特定地区可能发生的大地震所造成的灾害具有重要的作用.本文根据辽宁省海城地区的地质资料和发生于1975年2月4日辽宁省海城市的MS7.3地震资料,分别构造了海城地区的地下速度结构和海城地震的震源模型,并且使用可以准确描述地形起伏的曲线网格有限差分方法计算了海城地震的波场传播过程.通过对计算得到的波场快照、合成理论地震图以及地震烈度的分析表明：（1）震源模型、地下的速度结构和地形起伏对海城地震的波场传播模拟具有重要的影响,它们所产生的近断层效应、方向性效应和盆地效应明显;（2）通过计算得到的海城地震的理论烈度分布与通过震后调查得到的烈度分布大体符合,验证了本文所构造的震源模型和速度结构的合理性. 相似文献
6.
Anna A. Dobrynina Vladimir A. Sankov Larisa R. Tcydypova Victor I. German Vladimir V. Chechelnitsky Munkhuu Ulzibat 《Journal of Seismology》2018,22(2):377-389
A moderate shallow earthquake occurred on 5 December 2014 (M W = 4.9) in the north of Lake Hovsgol (northern Mongolia). The infrasonic signal with duration 140 s was recorded for this earthquake by the “Tory” infrasound array (Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Science, Russia). Source parameters of the earthquake (seismic moment, geometrical sizes, displacement amplitudes in the focus) were determined using spectral analysis of direct body P and S waves. The spectral analysis of seismograms and amplitude variations of the surface waves allows to determine the effect of the propagation of the rupture in the earthquake focus, the azimuth of the rupture propagation direction and the velocity of displacement in the earthquake focus. The results of modelling of the surface displacements caused by the Hovsgol earthquake and high effective velocity of propagation of infrasound signal (~ 625 m/s) indicate that its occurrence is not caused by the downward movement of the Earth’s surface in the epicentral region but by the effect of the secondary source. The position of the secondary source of infrasound signal is defined on the northern slopes of the Khamar-Daban ridge according to the data on the azimuth and time of arrival of acoustic wave at the Tory station. The interaction of surface waves with the regional topography is proposed as the most probable mechanism of formation of the infrasound signal. 相似文献
7.
L. P. Korsunova Yu. M. Mikhailov V. V. Khegai L. N. Leshchenko S. E. Smirnov V. V. Bogdanov 《Geomagnetism and Aeronomy》2010,50(7):920-926
We consider data obtained when the parameters of the ionospheric Es and F2 layers and the vertical gradient of the electric potential in the surface atmosphere were simultaneously measured
during the preparatory period of crustal earthquakes with M = 5.0–6.2 in the Kamchatka region. The appearance of anomalously high Es, accompanied by an increase in frequency parameters of the sporadic layer and the regular F2 layer, was detected on days
when possible earthquake precursors, as determined earlier, occurred in atmospheric electric fields. The presumed earthquake
precursors in the ionosphere are divided into two groups with different earthquake lead times ranging from several hours to
two weeks. Empirical dependences are presented that connect the lead time of an earthquake (from the moment of the appropriate
anomaly’s occurrence in the ionosphere or in the atmospheric electric field to the moment of the shock) and the epicentral
distance to the observation point with the earthquake magnitude. These dependences are different for the two groups of presumed
earthquake precursors, but they are close inside each group of possible precursors selected on the basis of quasistatic electric
field measurements and revealed in ionospheric parameter variations. 相似文献
8.
9.
以1998年1月10日的张北地震为例,应用小波变换及傅里叶分析,分析震中附近的6个地磁台站在地震前后共6个月的地磁场三分量分钟值采样数据.发现各个地磁台站记录的地磁场Z分量在张北地震前三个月内出现不同程度的异常现象,这种现象的出现频率随着离发震时间越近而越来越高,出现的地点由南向北迁移.地磁场H和D分量没有此类异常出现.用这6个地磁台出现异常时同一频率所对应的振幅值绘出等值曲线,得到的图形是稳定的四象限分布,震中基本上位于0～3nT的等值线上.结果表明小波分析是提取地震磁效应的有效工具,同时也证实了地震磁效应的客观存在. 相似文献
10.
11.
This study constructs a 3 D velocity structure model of the Ludian region in the Yunnan province, southwestern China, and simulates ground motion propagation of the 2014 Ludian Ms 6.5 earthquake. It aims to construct the local velocity structure of the Ludian region in three dimensions and with high precision. The simulation, using the spectral element method, is validated by field data from the Ludian earthquake records. Thus, it demonstrates that the adopted key parameters, such as the seismic source mechanism, propagation medium and geographical features of the engineering site, are appropriated for the simulation. Meanwhile, the simulation generates the ground motion distribution of the study region with an earthquakeinduced landslide in Ludian earthquake. 相似文献
12.
在临近大地震前,震源过程和前兆现象存在着一定的时间关系。本文从组合模式出发,利用断裂力学的应力一化学腐蚀理论来讨论临近大震前的震源过程和外因时震源过程的调制作用。在诸外因当中,为了研究宇宙线对地震的影响,本文具体分析了1965-1979年宇宙线μ介子强度变化的功率谱,首次得到了在所有周期分量中,准九天周期占有优势的结果。最后列举了宇宙线调制地震前兆的几个实例,并讨论了宇宙线对地壳中不稳定物质如过热液体暴沸的触发作用。 相似文献
13.
IntroductionMigration and inhomogeneity are important two of the characteristics in the temporal-spatial distribution of earthquake precursors, which have been dealt with by MEI, et al (1993) comprehensively with their proposed explanation. The obvious quadrant feature in spatial distribution of earthquake precursors has been drawn with the explanation for its mechanism developed in some case studies in recent years. This paper deals mainly with the quadrant features derived from the analysis… 相似文献
14.
15.
The apparent horizontal propagation velocity, that is the propagation velocity of seismic waves with respect to the ground surface, is discussed in this paper. This parameter is needed to determine the effects of earthquakes on long structures such as bridges and buried pipelines as well as the torsional rotation of foundations of multi-storey buildings. A time window intensity tensor introduced by Penzien and Kubo is used herein to determine the predominant directions of ground motion during an earthquake. Considering the reflection of waves at a free surface, an approximate relationship between the predominant direction and the angle of incidence of body waves with respect to the ground surface is presented. Knowing the material properties of the top layer and the angle of incidence, the desired propagation velocity with respect to the ground surface is readily calculated. The median value of the apparent propagation velocity of shear waves for near field sites which recorded the 1971 San Fernando earthquake was determined to be about 2-1 km/s using the above method. A similar value for the 1979 Imperial Valley earthquake is 3·7 km/s. These values are consistent with the range of values for the apparent propagation velocity determined by other researchers. 相似文献
16.
震前电磁辐射接收记录表明,河北张北地震前在北京,山西太原,河南安阳、洛阳记录到震前异常,这些异常全部在地震发生前结束,若在地震前能全面掌握这些异常,似能预报出河北张北地震。这些异常进一步表明电磁波接收仪能反映地震前兆。指出,为更好地发挥电磁波接收仪的作用,需要解决用计算机网络传递数据的问题。 相似文献
17.
本文从断裂系扩展的角度,研究了华北邢台、渤海、海城和唐山地震序列的发生过程.通过对前震-主震-余震地震活动图象的剖析,我们发现,这些地震序列是由不同长度、不同几何分布的相关断裂系相互作用和扩展的结果.根据地震活动图象和断裂扩展理论,对每个地震序列提出了相应的断裂系模式,并用断裂有限单元法将震源机制、地震活动图象的分期变化和大地形变等观测资料相结合,进行联合反演,再次对断裂系模式的几何和力学参数进行了修正,从而得到各个地震序列破裂过程的最佳结果.同时我们还发现,一个走滑大地震序列临近结束时,地震活动图象的总体轮廓呈现Z形.这是由于断裂系内的拐折扩展分支相互作用和连通成为一体的结果,这种总体Z形的出现,可作为地震序列结束的标志. 相似文献
18.
This study constructs a 3D velocity structure model of the Ludian region in the Yunnan province, southwestern China, and simulates ground motion propagation of the 2014 Ludian Ms 6.5 earthquake. It aims to construct the local velocity structure of the Ludian region in three dimensions and with high precision. The simulation, using the spectral element method, is validated by field data from the Ludian earthquake records. Thus, it demonstrates that the adopted key parameters, such as the seismic source mechanism, propagation medium and geographical features of the engineering site, are appropriated for the simulation. Meanwhile, the simulation generates the ground motion distribution of the study region with an earthquakeinduced landslide in Ludian earthquake. 相似文献
19.
煤矿矿震应力窗口效应 总被引：5，自引：0，他引：5
对煤矿矿震活动特征,震源机制解,与天然地震的相关性以及特殊的环境条件等进行了研究,认为煤矿矿震的孕育和发生受控于区域应力场,具有区域应力变化的灵敏窗口效应,可视为探索天然地震前兆和区域应力场变化的应力窗口。 相似文献
20.
Introduction
Many observation facts, rock-rupture experimental results, and theoretical research achievements proved that the sudden changes in ground deformation are the most possible earthquake short-term precursors.
The observed sudden changes in deformation that related to the earthquake preparation are here called the precursory. The sudden change is mainly characterized by the highly changing velocity and greatly accumulated deformation amplitude. 相似文献