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1.
Since 1979 the repeated observations and experiments of geomagnetic total intensity and vertical component have been carried
out for ten years in the geomagetic network which is located in Jiangsu Province, China. Three earthquakes aboveM
s 5.0 occurred during the decade, and some seismomagnetic effects were observed. The observation results show that the anomalies
of the vertical geomagnetic component can’t be observed untill some months before the earthquake (M
s>5.0) in this area.
In this paper it is suggested that a densely distributed network for continuous observation of geomagnetic vertical component
may catch seismomagnetic anomalies and thus improve earthquake prediction in the light of the geomagnetic measurements of
the mid — or — low latitude locations.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 80–87, 1991.
This study is sponsored by the Chinese Joint Seismological Science Foundation. 相似文献
2.
3.
The diurnal-variation anomalies of the vertical-component in geomagnetic field are mainly the changes of phase and amplitude
before strong earthquakes. On the basis of data recorded by the network of geomagnetic observatories in China for many years,
the anomalous features of appearance time of the minima of diurnal variations (i.e, low-point time) of the geomagnetic vertical components and the variation of their spatial distribution (i.e, phenomena of low-point displacement) have been studied before over 30 strong earthquakes with M
S≥6.6 such as Kunlunshan M
S=8.1 earthquake on November 14, 2001; Bachu-Jashi M
S=6.8 earthquake on February 24, 2003; Xiaojin M
S=6.6 earthquake on September 22, 1989, etc. There are good relations between such rare phenomena of geomagnetic anomalies and the occurrence of earthquakes. It has
been found that most earthquakes occur in the vicinity of the boundary line of sudden change of the low-point displacement
and generally within four days before and after the 27th or 41st day counting from the day of appearance of the anomaly. In
addition, the anomalies of diurnal-variation amplitude near the epicentral area have been also studied before Kunlunshan M
S=8.1 earthquake and Bachu-Jiashi M
S=6.8 earthquake.
Foundation item: National Science Technology Tackle Key Project during the Tenth Five-year Plan (2001BA601B01-05-04) 相似文献
4.
Using observational data of geomagnetic total intensity from 13 stations in the Beijing-Tianjin region, 3 stations in the
western Yunnan region of China, and 6 stations in California of U. S. A., the daily variations and their spectra of geomagnetic
total intensity were analyzed and compared. The results show that the morphology, the range and spectrum of daily variations
in geomagnetic total intensity are basically the same within the local extent of 100–200 km and are different in the large
extent of 500 km. The latitude factor of the daily variation range of geomagnetic total intensity is about 1–2 nT/degree within
the latitude extent of 25°–40°.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 83–89, 1992.
This work is supported by the State Seismological Bureau and the Chinese Joint Seismological Science Foundation, and U.S.
Geological Survey. 相似文献
5.
区域地磁在一定范围内,在排除空间环境、仪器本身故障等因素的前提下,各地磁台所观测到的地磁曲线是具一定相关性的,但强震孕震过程中会引起电导率等电磁性质发生改变,从而改变台站间地磁本应呈现出来的相关性,因此地磁异常可以为震前地震预报提供有用信息。以2013年7月22日岷县-漳县6.6级地震为研究对象,对其震前地磁前兆异常进行研究。分析表明:震前有明显的低点位移异常现象,且在此次异常后36天发生了6.6级地震;地磁Z值的每日一值空间相关分析也出现了明显异常,从空间上看,相关系数与地震震中有很好的对应关系,震中刚好处在相关系数最低的位置;且地磁台的密集程度对计算区域相关系数具有较大影响。 相似文献
6.
2018年10月16日新疆精河5.4级地震发生时,震中附近的台站不同程度上记录了地磁日变化畸变异常,如地磁总强度F02时每日一值空间相关异常、地磁垂直分量加卸载响应比异常、地磁低点位移以及地磁日变化空间相关异常等。统计震前观测到的所有地磁异常,并分析研究了其震前异常变化特征。得到如下结论:(1)从全国每日一值相关分析结果看,震前114天出现每日一值空间相关异常,异常高值台为乌鲁木齐和克拉玛依;(2)震前59天沿北天山断裂带分布的地磁台站加卸载响应比均成组出现超限的高值,且异常高值的空间分布跟震中位置有一定关联;(3)中国大陆地磁台站震前37天出现低点位移突变分界线,且异常集中于震中附近;(4)震前出现地磁垂直分量日变化空间相关异常,异常台站空间上也主要集中于北天山地区。因此地磁垂直分量日变形态及有关的计算方法短期内具有一定的预报效能,可为今后利用地磁方法预测地震积累经验和震例。 相似文献
7.
8.
A three-component geomagnetic survey was carried out during the period from 2002 to 2004 in China including Jiujiang-Ruichang region. Comparing the "2005.0 surface spline model of China geomagnetic field" created on the basis of the survey data with the "1970.0 surface spline model of China geomagnetic field", we can see an obvious abnormity in the geomagnetic horizontal component within a range of about 100 km around the epicenter of the Ms=5.7 Jiujiang-Ruichang earthquake occurred on November 26, 2005. After the earthquake, we carded out a repeated geomagnetic survey at 21 stations in the Jiujiang-Ruichang region and created a corresponding "2005.0 partially revised surface spline model of China geomagnetic field". By comparing the above three models, analyzing the geomagnetic horizontal component at the profile in the Jiujiang-Ruichang region and quantitatively studying the geomagnetic data of every stations around the Ms=5.7 earthquake, we have obtained the geomagnetic abnormity associated with this earthquake. Then the geomagnetic abnormity and its relation with seismic activity are discussed in this paper. 相似文献
9.
In this paper, the two metnods, rectangular spectrum (RS) and maximum entropy power spectrum (MES), have been used in calculating
the geomagnetic structures of the crust in Haicheng and its adjacent areas and carrying out the geomagnetic stratification
of the crust. The result of the research indicates that the crust can be devided into such three layers as nonmagnetic layer,
magnetic layer and regressive magnetic layer from the top to the bottom. It is also found the distribution of the geomagnetic
bottom interface (Curie surface) is consistent with the lower interface of the upper crust and the top interface of the middle
crust of the velocity structure of the crust. It is very interesting that the Haicheng earthquake of Feb. 4, 1975,M 7.3 occurred at the depth gradient belt of the Curie isotherm surface. So, to research on the geomagnetic layers and the
distribution characteristics of the Curie isotherm surface is meaningful in judging potential seismic foci.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 448–454, 1993.
The data of velocity and electricity materials used in this paper are as reference from the related materials of the maps
and directions etc. of Donggou-Haicheng-Dong Ujimqin Qi Geoscience Transect by Prof. Zao-Xun LU, Huai-Kuan XIA and others. 相似文献
10.
"Double low-points" anomaly in daily variation of vertical component of geomagnetic field before the MS8.0 Wenchuan earthquake
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The "double low-points" anomaly in daily variation of vertical geomagnetic component was observed on May 9, 2008 at 13 geomagnetic observatories belonging to the geomagnetic observatory network center of China Earthquake Administration. These observatories distribute roughly on three belts with the intersection in western Sichuan. On May 12, three days after the anomaly appearance, the great MS8.0 Wenchuan earthquake occurred. The "double low-points" anomaly in daily variation of vertical geomagnetic component is an anomalous phenomenon of regional geomagnetism, which does exist objectively. The possible cause is the change of extrinsic eddy current system resulting in geomagnetic daily quiet variation (Sq), or the delay of several hours between the intrinsic and the extrinsic eddy current systems. The relationship between the "double low-points" anomaly of daily geomagnetic variation and the earthquake reveals that the former possibly reflects the accelerative alteration of earthquake gestation in the deep Earth. 相似文献
11.
Time changes in transfer functions of short period geomagnetic variations in 28 years from 1960 through 1987 are studied,
systemically and in detail in this paper. The results indicate that: (1) It is evident that seasonal and secular changes in
the transfer functionsA at exist the Guangzhou Geomagnetic observatory. The characteristics for seasonal changes are large in summer and smaller
in winter with main cycles of 12 and 6 months. The characteristic for secular change is a descend with a rate of 0.0025 per
year. The seasonal and secular changes in transfer functionsB are not evident. (2) The direction of Parkinson vector at Guangzhou geomagnetic observatory is clearly affected by the ocean,
and is associated with coastal effect. (3) The values of the transfer function A and B are related to geomagnetic activity
ata=0.05. Secular change is not related to geomagnetic activity, maybe it is affected in a great measure by earth conductivity
change.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica sinica,13, 480–488, 1991.
This study is part supported by Chinese Joint Seismological Science Fundation. 相似文献
12.
使用江苏地区9个地磁台站2009年1月~2016年10月的分钟值数据,计算得到各台站的地磁谐波振幅比时间序列变化曲线。分析发现,2012年7月20日高邮4.9级地震、2016年10月20日射阳4.4级地震前,高邮台和盐城台地磁谐波振幅比YZH_x和YZH_y分别出现了长短周期不同步的异常变化。其异常特征表现为:(1)异常的长期变化形态为"下降—转折—恢复",在恢复过程中出现不同步现象,异常持续时间近3年,异常幅度为0.02~0.17;(2)YZH_y向的异常幅度大于YZH_x向,同时,2次地震主震的主压应力方向为EW向,存在异常幅度较大方向与主压应力方向一致的特点。 相似文献
13.
14.
2017年精河MS6.6地震前地磁异常特征分析 总被引:1,自引:0,他引:1
2017年8月9精河发生MS6.6地震,距震中300km范围内的温泉台、克拉玛依台、乌鲁木齐台捕捉到此次地震前的地磁异常信息,本文对此进行了分析和总结,结论如下:①地磁谐波振幅比反应了观测点深部电阻率变化,2016年呼图壁MS6.2、此次精河MS6.6地震均发生在克拉玛依台地磁谐波振幅比异常下降之后的转折和恢复阶段;②震前83天、21天沿北天山断裂带分布的地磁台站逐日比和加卸载响应比均成组出现超限的高值,且异常高值的空间分布与震中位置有一定关联;③全国大陆地磁台站震前34天出现低点位移突变分界线,且异常集中于震中附近。 相似文献
15.
选取恩施台、涪陵江东台、石柱黄水台以及武隆仙女山台2012年1月至2017年11月地磁数据进行异常分析,得到各个台站的地磁谐波振幅比和加卸载响应比计算结果,并结合2017年11月23日重庆武隆M5.0地震震中附近地质构造背景分析地震前后地磁异常现象。分析结果认为大部分地磁谐波振幅比变化特征类似于地电阻率的变化特征,表现为"下降-转折-上升"过程。本次地震大致发生在转折上升的初期阶段,其中震中距较小的台站地磁谐波振幅比变化趋势不同步,但变化幅度大致相同,而震中距较大的台站地磁谐波振幅比变化趋势较为同步,变化幅度较大。此外,研究还表明震前地磁加卸载响应比异常高值在时空分布上与震中位置具有很好的对应关系。 相似文献
16.
In this paper, the coefficients of Parkinson vectora, b and the in-phase partA
r, Br and quadrature-phase partA
i, Bi of transter functions are calculated by using two kinds of data processing methods, respectively. The results of both methods
are close to each other. All these six parameters above are low in value, showing that the electric structure in Heze area
is rather uniform. It seems that the anomalous changes appeared in both results, and the values of parameters decrease before
and after Heze earthquake.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 113–120, 1991. 相似文献
17.
Significant anomalies were observed at the geomagnetic stations in the southwest region of China before the Yingjiang MS6.1 earthquake and the Ludian MS6.5 earthquake in 2014. We processed the geomagnetic vertical component diurnal variation data by the spatial correlation method. The results show that during the period from April 1 to May 20, 2014,there existed quasi-synchronous decrease changes in the coefficient curves between the five geomagnetic stations of Guiyang,Hechi,Nanshan,Muli,Yongning and Xinyi and Hongshan stations.Furthermore,there was a high gradient zone in the normalized correlation coefficient contour map with background values removed. The epicenters of the Yingjiang MS6.1 earthquake and the Ludian MS6.5 earthquake are located in the gradient zone or near the gradient zone. 相似文献
18.
Power spectral characteristics of the seismic activities before and after the seven large earthquake — Haicheng, Tangshan,
Lancang, Longling, Mabian, Puer and Songpan are studied by spectrum analysis method. The results show that they all have continuous
power spectrum and aperiodic behaviour. When the time away from the large earthquake occurrence, the characteristics of the
seismic activities are obviously accompanied by stochastic components. About one year before main shock, the moving orbits
constructed by spectrum amplitudes showed the contracting tendency. And the properties during that time may display as flicker
noise. One’s another time almost mixed whole phase space. But the essence of seismic activities after main shocks is a chaotic
state accompanied with much noises.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 276–281, 1993.
This subject is supported by the Chinese Joint Seismological Foundation. 相似文献
19.
The effect of stress on pore pressure in rocks and the mechanism of water table anomaly before earthquakes 总被引:1,自引:0,他引:1
Triaxial compressive experiments of porous rock samples were carried out under various confining pressures and initial pore
pressures without drainage; axial strain and pore pressure were observed versus differential stress. The results of such experiments
show that pore pressure increases with increase of differential stress at low differential stress; pore pressure decreases
with increase of differential stress at medium and high differential stress. Pore pressure also increases with large amplitude
decrease of differential stress at high differential stress. Based on such experiments, it is suggested that water table anomaly
before an earthquake reflects the change of differential stress in crustal rocks. The anomalous behavior of water tables in
the epicentral and peripheral areas before the great Tangshan earthquake of July 28, 1976 are explained by such suggestion.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 88–95, 1991.
This study is supported by the Chinese Joint Seismological Science Foundation. Professor Yongtai Che gave us much help in
applying fund support and supplying earthquake case histories. 相似文献
20.
In this paper, the major idea is: when seismic stress accumulates to a certain extent, a stick slip earthquake will occur
on the fault plane. The seismic stress before and after the stick slip earthquake occurrence are both stochastic variables.
According to this idea, the model of double bounds of stochastic stress is proposed, and also it is used to analyse the seismic
risk of Xian Shui River Fault Zone in the coming 30 years, the result is similar to what the Seismological Bureau of Sichuan
Province has predicted.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 477–483, 1993. 相似文献