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1.
A type of relatively low frequency ULF magnetic disturbance has been generally observed by the magnetic induction-meter since
it’s operation at Baijiatuan observatory in Beijing. As the amplitudes and frequencies of such disturbance signals change
with time and are different from the disturbances produced by some man-made magnetic sources, therefore they are usually taken
as a kind of earthquake precursors for ULF electro-magnetic emission. However, a comparative analysis with magnetic storms
on the magnetogram obtained by variometerat the same station indicates that such signals always occur in the period of magnetic
storm occurrence and so far we have not found the cases where such signals occur with no magnetic storms, therefore this kind
of ULF magnetic disturbances should not be taken as a ULF earthquake precursors of the electromagnetic emission at present.
The main features of such signals are as follows: the signals occur discontinuously during storms and the duration of each
time section with such signals and the occurrence rates of the sections and the disturbance amplitudes are usually related
to the types and intensities of storms. The wave form characteristics of the ULF disturbance are also related to the types
of storms. Generally, the amplitudes and durations for SC storms are stronger and longer respectively than those for GC stroms,
and if a storm is with largerK index, then relatively large amplitudes and higher rates and longer durations as well as variable frequencies will be observed
andvice versa. Most of the start time and the time section with strongest disturbance recorded by the ULF unit and by the variometer are
not consistent with each other, and the same one is only about 44%. The periods and intensities of such disturbance signals
are in the ranges of few to several seconds and 0.04–8 nT respectively. The predominant frequency is about 0.06 Hz and certain
energies are also distributed on the harmonic frequencies.
Contribution No. 95A0063, Institute of Geophysics, SSB, China. 相似文献
2.
The time-frequency analysis and anomaly detection of wavelet transformation make the method irresistibly advantageous in non-stable
signal processing. In the paper, the two characteristics are analyzed and demonstrated with synthetic signal. By applying
wavelet transformation to deformation data processing, we find that about 4 months before strong earthquakes, several deformation
stations near the epicenter received at the same time the abnormal signal with the same frequency and the period from several
days to more than ten days. The GPS observation stations near the epicenter all received the abnormal signal whose period
is from 3 months to half a year. These abnormal signals are possibly earthquake precursors.
Foundation item: Joint Seismological Science Foundation of China (604021) and National Natural Science Foundation of China (40074024). 相似文献
3.
Introduction The study mainly focused on tidal information, i.e. earth tide in the continuous deformationdata processing and analysis before. And the analysis methods used were specially for earth tideonly. As to the medium-long period and non-tidal information, fitting and filtering are not the bestmethods. Because they are not able to reflect the variation process of frequency information withtime and to distinguish and extract more earthquake information, although they can eliminateyea… 相似文献
4.
Ultra low frequeney electromagnetic wave anomaly and its spectrum characteristics before earthquakes
ＵｌｔｒａｌｏｗｆｒｅｑｕｅｎｅｙｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｗａｖｅａｎｏｍａｌｙａｎｄｉｔｓｓｐｅｃｔｒｕｍｃｈａｒａｃｔｅｒｉｓｔｉｃｓｂｅｆｏｒｅｅａｒｔｈｑｕａｋｅｓＪｉａｎ－ＧｕｏＨＡＯ；Ｙｕｎ－ＦｕＺＨＡＮＧ；Ｈｕａｉ－ＷｅｎＰＡＮ；... 相似文献
5.
基于法国DEMETER卫星观测的超低频(ULF)电场波形, 本文提出了更简单易实施的ULF电场扰动预处理方法. 利用该方法, 对文献中已报道的2010年2月27日智利MS8.8地震前的ULF电场扰动进行了更全面的分析. 结果表明: 已报道的20°S—40°S地磁纬度带内的ULF电场扰动并非仅出现在最靠近震中的半轨道, 而是出现在较大的经度范围内. 大范围ULF电场扰动的区域正好位于南大西洋异常区, 很可能受到该区域异常磁场的影响. 南大西洋异常中心区域的ULF电场扰动表现出共轭特征, 即在南北地磁纬度20°—40°范围内ULF电场均出现约5 mV/m的扰动, 北纬地区的ULF电场扰动幅度相比南纬地区更小. 而在南大西洋异常中心区域外的ULF电场扰动则仅在20°S—40°S地磁纬度带内出现, 在其共轭区并未观测到ULF电场扰动. 这可能是由于南大西洋异常中心区域外的ULF电场扰动幅度比中心区域更小所致, 在电离层中由于碰撞效应更易被衰减, 因此ULF电场扰动无法传播至其共轭区. 本文的方法和结果可为后续更全面地分析卫星在电离层高度记录的ULF电场扰动提供参考. 相似文献
6.
Ultra low frequency electromagnetic wave anomaly and its spectrum characteristics before earthquakes 总被引：1，自引：0，他引：1
Jian-Guo Hao Yun-Fu Zhang Huai-Wen Pan De-Rui Li Tian-Ming Tang Xiao-Qin Liu 《地震学报(英文版)》1995,8(1):101-109
Many observations and researches show that abundant and intense ultra low frequency (ULF) electromagnetic anomalies appeare
before local earthquakes. In order to understand this phenomenon systematically, the transmission property and the formation
of the seismic-electric dipole are discussed in this paper. The results show that the vertical component of the ULF electric
anomaly before earthquake has the properties of better penetration, less disturbance and high signal-to-noise ratio. The signal
can be easily extracted and received. The anomaly should be an important way to seek for reliable short-term and imminent
earthquake precursors. After the spectrum analysis of the (ULF) electric field anomalies, we found that the periods of the
anomaly related to local earthquakes are from a few minutes to a dozens minutes. There is a relation between the spectrum
of the anomaly and the epicentral distance. The ULF electric field anomalies strongly rely on the orientation of the seismogenic
zone. The percolation electric field anomaly and its spectrum amplitude do not have obvious relation with the size of local
earthquakes.
Contribution No. 94A0097, Institute of Geophysics, SSB, China.
The English version is improved by Prof. Guo-Hua FAN, Institute of Geophysics, State Seismological Bureau. 相似文献
7.
V. A. Mullayarov L. M. Abzaletdinova V. V. Argunov A. A. Korsakov 《Geomagnetism and Aeronomy》2011,51(6):825-834
The specific features of a method for radiosounding the lower ionosphere over earthquake epicenters using LF electromagnetic
signals of thunderstorm sources (atmospherics) have been considered. The effects of shallow-focus earthquakes with magnitudes
larger than 4.0 and their precursors manifest themselves in amplitude characteristics of atmospherics. It has been assumed
that variations in the signal characteristics are related to disturbances in the lower ionosphere. According to the results
of azimuthal scanning, cross-sectional dimensions of disturbed regions, as a rule, correspond to the dimensions of the first
two Fresnel zones for signals at a frequency of 10 kHz. Azimuthal scanning also indicated that the positions of disturbed
regions during and before earthquakes could have a certain dynamics and differ from the projection onto the earthquake epicenter.
The ratio of the amplitudes of electric and magnetic signal components, in the variations of which seismic effects before
earthquakes can also be observed, has been considered. An analysis of the ratio makes it possible to increase the probability
of predicting earthquakes when using the characteristics of the electromagnetic signals of lightning discharges as an additional
method of complex monitoring of disturbances in the lower ionosphere caused by seismic processes. 相似文献
8.
The anomalies of electric-magnetic field and self-potential before earthquakes are important precursory phenom-ena.A simulating experiment study on the variations in ultra-low frequency(ULF)magnetic field and self-poten-tial during rock cracking was carried out in a magnetic field-free space.The results revealing in detail the whole process of the occurrences of electric and magnetic anomalises are significant for understanding the microscopic mechanism of ULF electric and magnetic signals.The experiment indicated that at the initial stage the slow changes in strain.self-potential and magnetic field with small amounts appeared firstly near the source of initial cracking,and then extended as the crack developed on.In the time domain,the self-potential anomaly emerged first and ULF magnetic field changes arose then.The shape of the ULF electric and magnetic anomaly varied ob-viously in early-,mid-and late-term of the test.The authors attributed the pulse-like changes of self-potential to the generationj and movement of the accumulated electric charges during the cracking caused by charge separation on the crack tips within the sample.While the magnetic pulses of shorter-period at the last stage of the test,may be induced by instantaneous electric current of the accumulated charege during the cracking acceleration.The technical method and the observational results of this experiment are given in detail and the microscopic mechanism of elec-tric and magnetic precursors before earthquake are discussd in the present paper as well. 相似文献
9.
震前电磁场和大地自电位的异常是重要的地震前兆现象．在零磁空间对超低频段的磁场和自电位的变化进行了岩石破裂的实验研究，细致地揭示出电场、磁场出现异常变化的全过程，对深入认识超低频电磁信号的微观机理具有重要的意义．实验发现，岩石受力后应变、电位和磁场的缓慢变化在空间分布上是首先在近破裂源处出现，继而随裂纹的发展而改变位置；在时间序列上先出现自电位异常，然后是超低频磁场的变化；在异常形态上，超低频电磁信号呈现出早期、中期、晚期3个阶段的明显差异．研究表明，岩石微破裂引起裂隙尖端处的电荷分离. 静电荷在局部区域的积累和运移，导致了自电位的脉冲状变化；而在主破裂阶段，积累电荷的急速运动形成瞬间电流，激发了脉冲式的磁场异常．本文详细介绍了这一综合实验的技术步骤和观测结果，并对地震电磁前兆的微观机理进行了探讨． 相似文献
10.
Katsumi Hattori Peng Han Chie Yoshino Febty Febriani Hiroki Yamaguchi Chieh-Hung Chen 《Surveys in Geophysics》2013,34(3):293-316
In order to clarify the ultra low frequency (ULF) seismo-magnetic phenomena, a sensitive geomagnetic network has been installed in Kanto, Japan. In this study, we have analyzed geomagnetic data observed during the past decade in Izu and Boso Peninsulas. Energy of ULF geomagnetic signals at the frequency around 0.01 Hz has been investigated by wavelet transform analysis. To identify anomalous changes in ionospheric disturbances, the station Memabutsu has been chosen as a reference station. Case studies of magnitude 6 class earthquakes have demonstrated that there are unusual geomagnetic energy enhancements in the vertical component before the main shocks. Statistical studies by superposed epoch analysis have indicated that, before a sizeable earthquake, there are clearly higher probabilities of ULF anomalies than after the earthquake: statistical results of daily counts were found significant at about 3–4 weeks before, 1 week before, few days before, and 1 day after the event for Seikoshi station in Izu and around 2 weeks before, few days before, and 1 day after the event for Kiyosumi station in Boso, respectively. 相似文献
11.
华北地震活动中短期异常图像研究 总被引：2，自引：0，他引：2
系统研究了多种地震活动性方法后认为, 1970年以来华北地区发生的MS≥5.8中强震前, 约83%具有3级或4级地震异常条带、 孕震空区及信号震出现。 震前有信号震的比例占92%, 83%的信号震距主震150 km以内, 距主震发生时间小于1年的占67%。 条带时间形成进程在2年内的约占90%, 震前条带形成后到主震发生83%在5个月内。 空区形成进程在1年半内的占83%, 空区形成后到主震发生91%在50天内, 为有意义的地震活动图像短期异常特征。 文中还探讨了异常条带图像的定量判别指标及其与未来强震的关联。 相似文献
12.
本文介绍了应用电磁反馈零位检测技术改装的重力仪进行高频信息的观测。阐述重力仪高频信息频谱分布特征、数据采集、数字计算和随机信息的处理方法。利用高频信息可以很好地观测和研究地脉动,给出北京香山地震台利用重力仪高频信息观测所得的地脉动功率谱。分析了地脉动特征及其与台风过程的关系;讨论了某些大地震前所出现的地脉动异常现象。得出北京地区正常地脉动频率分布范围为0.13-0.32Hz,优势频率为0.2Hz,相应的卓越周期为5s的脉动频率异常,也可能在地脉动的正常频率处（0.2Hz左右）,出现幅度很大的脉动幅度异常,后者又往往与台风引起的幅度异常相混淆。 相似文献
13.
空间电场信号异常识别是研究地震引起电离层扰动的重要内容。 将空间超低频电场电位数据看作随机数字信号, 以均值、 均方差、 偏度和峰度等四个指标进行描述, 采用“5·12”汶川大地震前空间超低频电场电位数据作为原始数据, 训练改进型BP神经网络, 建立了空间电场信号异常分类识别模型, 并以SOM神经网络进行验证。 计算结果显示, 空间超低频电场电位异常信号主要集中在5°~25°N, 88°~120°E之间的区域, 汶川大地震影响范围内的电离层扰动, 可能是汶川地震发生前引起的, 这与前人研究一致, 说明采用改进型BP神经网络异常分类识别模型研究地震引起的电离层扰动是可行的。 相似文献
14.
There are many reports about the abnormal electromagnetic signals observed before great earthquakes. In particular, the signals of electromagnetic anomalies before the Hyogo-Ken Nanbu, Japan, MS=7.2 earthquake on January 17, 1995 (Hayakawa, et al, 1996) and those before the Loma Prieta, USA, MS=7.1 earthquake on October 19, 1989 (Fraser-Smith, et al, 1990) are especially remarkable. However, what the above authors reported are only the phenomena of one or two observatories. In order to … 相似文献
15.
哈尔滨市延寿地震台竖直摆倾斜仪资料分析 总被引：1，自引：0，他引：1
介绍了哈尔滨市延寿地震台竖直摆倾斜仪的工作状态,列举了该仪器记录到的多次同震应变阶。分析认为:这种阶跃变化反映了地震因释放应变能而改变了地壳的应变场;从阶变图象可以看出:中强远震的同震阶变幅度较小,中强近震同震阶变的相对幅度较大,同等震级震中距越小,阶变幅度也越大。证明了近震对观测点(台站)附近区域应力场改变大于远震。同时,展示了2005年7月25日黑龙江省林甸县M5.1级地震的短期异常及临震异常变化图象,发现短期异常和临震异常的形态非常类似,但同一方向(分量)仪器对两次异常的响应程度却截然不同,这可能与此次地震孕育过程不同阶段的地壳应力调整和应力场变化密切相关。 相似文献
16.
17.
On the Generation of ULF Magnetic Variations by Conductivity Fluctuations in a Fault Zone 总被引：1，自引：0，他引：1
G. D. Egbert 《Pure and Applied Geophysics》2002,159(6):1205-1227
v--vPrior to the October 18, 1989 Loma Prieta Ms 7.1 earthquake, Fraser-Smith et al. (1990) recorded a 10-100 fold increase in ultra-low frequency (ULF) magnetic fields near the earthquake epicenter. Several mechanisms for generation of these ULF fields by fluid flow in the earth have been advanced, but all appear to require unrealistic fluid velocities or hydraulic permeabilities to match the observations. As an alternative explanation, Merzer and Klemperer (1998) proposed that the increase in ULF magnetic fields could result from induced electric currents flowing in a fault-zone made temporarily much more electrically conductive by stress-induced reorganization of pore geometry. Using a numerical model we show that while this mechanism could produce a significant increase in ULF variations, mutual induction between the fault zone and the surrounding crust would probably limit the amplitude increase to levels well below those observed at Loma Prieta. We consider a variant on this quasi-static conductive fault zone model in which low frequency telluric currents are modulated by small higher frequency variations of bulk fault zone conductivity. We show that because the spectrum of natural EM variations is red, substantially larger relative increases in ULF magnetic fields could be produced by this mechanism with even small conductivity fluctuations at these frequencies. These variations would be easy to detect with a well-designed experiment, if they occurred. In principle this mechanism could explain the Loma Prieta ULF observations, however the magnitude of conductivity fluctuations that would be required to match the very large reported amplification factors still appears to be too large to be physically plausible. 相似文献
18.
本文搜集与整理了我国几十次大、中强地震,震前、震时的地倾斜异常图象,按其形态大致可分为五类:Ⅰ.震前倾斜记录曲线渐变——回复——发震(多见于远震);Ⅱ.震前倾斜记录曲线突变(阶跃)——发震(多见于近震);Ⅲ.震前倾斜记录曲线扰动或单向脉冲——正常——发震;Ⅳ.震前倾斜潮汐记录曲线畸变——发震;Ⅴ.震前倾斜记录曲线脉动(曲线加粗)——发震,其特征为:1.异常形态呈多样性;2.异常出现在震前几分钟到几十小时;3.异常幅值一般在几毫秒至十分之几角秒(10-8——10-6rad),个别达几角秒(10-5rad);4.异常倾斜方向多半与震中方位有关;5.异常有由远及近、从外到内(震中)的迁移现象。文章作者还结合模拟实验和地震模式,讨论了地震前倾斜异常的有关问题。 相似文献
19.
The long-time practice of observational research on earthquake prediction has shown that the information on short-term and
imminent earthquake precursors can hardly be detected, but it is very important for practical and effective earthquake prediction.
The result of analysis and study in this paper has shown that the anomaly of quasi-static atmospheric electric field may be
a kind of reliable information on short-term and imminent earthquake precursors. On such a basis, the 20 years’ continuous
and reliable data of atmospheric electric field observed at the Baijiatuan seismic station are used to study the correlation
between the anomalies in seismic activity and relative quiet periods bear on the occurrence of near earthquakes within 200
km range around Beijing after the Tangshan earthquake. The observational results recently reported before hand in written
form and earthquakes that actually occurred in near field in corresponding time periods are compared and analyzed. The efficacy
of these written prediction opinions about near earthquakes in the recent 10 years is tested. From the test results, the brilliant
prospect that the anomaly of quasi-static atmospheric electric field may really become a reliable mark for making short-term
and imminent earthquake predictions is discussed. Besides, as a preliminary step, some judgment indexes for predicting earthquakes
by use of the observational data of atmospheric electric field before earthquakes are put forward. In the last part, it is
pointed out that it would be possible to obtain more believable judgment indexes for determining the three elements of near
earthquakes before greater earthquakes (M
S≥5) only if a relatively reasonable station network (2–4 stations every 10 000 km2) is deployed and further investigation is made.
Contribution No. 97A0040, Institute of Geophysics, State Seismological Bureau, China.
This subject is sponsored by Program No. 95-04-05-01-04, State Seismological Bureau, China. 相似文献