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1.
任熙宪 《地震学报(英文版)》2006,19(1)
Introduction It is well known that the local geomagnetic field would change during the pregnancy of an earthquake, which may be associated with the change of the electromagnetic impedances of the crust medium. This phenomenon has been paid attention for a long time and up to now a lot of work both in observation and theory of tectonomagnetism has been carried out and much progress has been achieved (Stacey, 1964; Johnston, 1978; QI, 1977; Rikitake et al, 1980; Shapiro and Ab-dullabekov, 1982… 相似文献
2.
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
3.
4.
The terrestrial noise in the differencial data of geomagnetic total field recorded at 21h in North China was fitted by using
the geomagnetic vector data from Beijing Observatory. The terrestrial noise level and its spatial feature in this region was
discussed. A method, which may be useful for justifying the quality of fitting, was provided in this paper. The analysis indicates
that the terrestrial noise is one of the important noise in tectonomagnetic study. It is shown that the susceptibility effect
is quite small and the orientation effect is the main component in the terrestrial noise in North China. The rough spatial
feature of the magnetic anomaly in crustal substance was infered from the spatial feature of terrestrial noise. The measurement
precision and the source noise level of data at 21h in this region were obtained in the analysis of residual noise.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 441–447, 1993. 相似文献
5.
Using the minute data of the H component of geomagnetic field from the 20°E magnetic meridian chain and the 30°N magnetic latitudinal chain, the temporal evolution characteristics of the equatorial ring current during the storm on November 7-10, 2004 are studied. It is indicated that the UT-MLT and UT-MLAT graphics extremely exhibit the local time distribution, latitudinal variation and temporal evo- lution of the H component. The results show: (1) The UT-MLT contour clearly shows the increasing of the H component mostly around noon during the initial phase, representing the geomagnetic effect from the magnetopause current system. During the main phase, most negative values of the H com- ponent appear around the dusk-side, indicating the dawn-dusk asymmetric distribution of the ring cur- rent. (2) The contour of UT-MLAT suggests the latitudinal variation of the H component decreasing with the enhancement of the latitudes during geomagnetic storm, which is in good agreement with the Dst index. The latitudinal variations provide a new sight for describing the temporal characteristics of the intensity of the storm-time ring current. (3) Both the contours of UT-MLT and UT-MLAT are useful to monitor the space-time distribution of the equatorial ring current. 相似文献
6.
ＩｎｔｒｏｄｕｃｔｉｏｎＩｔｉｓｋｎｏｗｎｔｈａｔｔｈｅｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｉｍｐｅｄａｎｃｅｓｏｆｔｈｅｃｒｕｓｔｍｅｄｉｕｍｍａｙｂｅｃｈａｎｇｅｄｄｕｒｉｎｇｔｈｅｐｒｅｇｎａｎｃｙｏｆａｎｅａｒｔｈｑｕａｋｅ,ａｎｄｍａｙｌｅａｄｔ... 相似文献
7.
The dependence of the origination of G conditions in the ionospheric F region on solar and geomagnetic activity has been determined based on numerical simulation of the ionosphere over points
50° N, 105° E and 70° N, 105° E for summer conditions at noon. It has been found that the threshold value of the Kp geomagnetic activity index (Kp
S
), beginning from which a G condition can originate, is minimal for a low solar activity level at relatively high latitudes during the recovery phase
of a geomagnetic storm. On average, Kp
S
increases with increasing solar activity, but G conditions can originate at high solar activity levels and be absent at moderate ones for certain Kp values, which was apparently predicted for the first time. These properties of the origination of G conditions do not contradict the known results of a G-condition statistical analysis performed based on the data from the global network of ionospheric stations. 相似文献
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.
ＧｅｏｍａｇｎｅｔｉｃｓｏｌａｒｆｌａｒｅｅｆｆｅｃｔｏｎＦｅｂｒｕａｒｙ４ａｎｄ６，１９８６ａｔｔｈｅｃｈｉｎａＡｎｔａｒｃｔｉｃＧｒｅａｔｗａｌｌＳｔａｔｉｏｎＸｉａｏ－ＰｉｎｇＺＥＮＧａｎｄＹｕｎ－ＦａｎｇＬＩＮ（曾小苹，林云芳）（Ｉｎｓｔｉｔ... 相似文献
10.
Based on digital teleseismic P-wave seismograms recorded by 28 long-period seismograph stations of the global seismic network,
source process of the November 14, 2001 western Kunlun Mountain M
S=8.1 (M
W=7.8) earthquake is estimated by a new inversion method. The result shows that the earthquake is a very complex rupture event.
The source rupture initiated at the hypocenter (35.95°N, 90.54°E, focal depth 10 km, by USGS NEIC), and propagated to the
west at first. Then, in several minutes to a hundred minutes and over a large spatial range, several rupture growth points
emerged in succession at the eastern end and in the central part of the finite fault. And then the source rupture propagated
from these rupture growth points successively and, finally, stopped in the area within 50 km to the east of the centroid position
(35.80°N, 92.91°E, focal depth 15 km, by Harvard CMT). The entire rupture lasted for 142 s, and the source process could be
roughly separated into three stages: The first stage started at the 0 s and ended at the 52 s, lasting for 52 s and releasing
approximately 24.4% of the total moment; The second stage started at the 55 s and ended at the 113 s, lasting for 58 s and
releasing approximately 56.5% of the total moment; The third stage started at the 122 s and ended at the 142 s, lasting for
20 s and releasing approximately 19.1% of the total moment. The length of the ruptured fault plane is about 490 km. The maximum
width of the ruptured fault plane is about 45 km. The rupture mainly occurred within 30 km in depth under the surface of the
Earth. The average static slip in the underground rocky crust is about 1.2 m with the maximum static slip 3.6 m. The average
static stress drop is about 5 MPa with the maximum static stress drop 18 MPa. The maximum static slip and the maximum stress
drop occurred in an area within 50 km to the east of the centroid position.
Foundation item: Joint Seismological Science Foundation of China (103066) and Foundation of the Seismic Pattern and Digital Seismic Data
Application Research Office of Institute of Earthquake Science of the China Earthquake Administration. 相似文献
11.
On July 20, 1995, an earthquake of M
L=4.1 occurred in Huailai basin, northwest of Beijing, with epicenter coordinates 40.326°N, 115.448°E and focal depth 5.5 km.
Following the main shock, seismicity sharply increased in the basin. This earthquake sequence was recorded by Sino-European
Cooperative Huailai Digital Seismograph Network (HDSN) and the hypocentres were precisely located. About 2 hours after the
occurrence of the main shock, a smaller event of M
L=2.0 took place at 40.323°N, 115.447°E with a focal depth of 5.0 km, which is very close to the main shock. Using the M
L=2.0 earthquake as an empirical Green’s function, a regularization method was applied to retrieve the far-field source-time
function (STF) of the main shock. Considering the records of HDSN are the type of velocity, to depress high frequency noise,
we removed instrument response from the records of the two events, then integrated them to get displacement seismogram before
applying the regularization method. From the 5 field stations, P phases in vertical direction which mostly are about 0.5 s
in length were used. The STFs obtained from each seismic phases are in good agreement, showing that the M
L=4.1 earthquake consisted of two events. STFs from each station demonstrate an obvious “seismic Doppler effect”. Assuming
the nodal plane striking 37° and dipping 40°, determined by using P wave first motion data and aftershock distribution, is
the fault plane, through a trial and error method, the following results were drawn: Both of the events lasted about 0.1 s,
the rupture length of the first one is 0.5 km, longer than the second one which is 0.3 km, and the rupture velocity of the
first event is 5.0 km/s, larger than that of the second one which is about 3.0 km/s; the second event took place 0.06 s later
than the first one; on the fault plane, the first event ruptured in the direction γ=140° measured clockwise from the strike
of the fault, while the second event ruptured at γ=80°, the initial point of the second one locates at γ=−100° and 0.52 km
from the beginning point of the first one. Using far-field ground displacement spectrum measurement method, the following
source parameters about the M
L=4.1 earthquake were also reached: the scalar earthquake moment is 3.3×1013 N·m, stress drop 4.6 MPa, rupture radius 0.16 km.
Contribution No. 99FE2022, Institute of Geophysics, China Seismological Bureau.
This study is supported by the Chinese Joint Seismological Science Foundation (95-07-411). 相似文献
12.
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
13.
Based on satellite observation data, using dynamics equation, the ionospheric O+ ion’s distribution in the synchronous altitude region for different geomagnetic activity indexK
p is studied by theoretical modeling and numerical analyzing, and semi-empirical models for the O+ ion’s density and flux versus longitude in the synchronous altitude region for differentK
p
are given. The main results show that in the synchronous altitude region: (i) The O+ ion’s density and flux in day-side are larger than those in nightside. (ii) With longitude changing, the higher the geomagnetic
activity indexK
p
is, the higher the O+ ion’s density and flux, and their variation amplitude will be. The O+ ion’s density and flux whenK
p ≥ 6 will be about ten times as great as that whenK
p
= 0. (iii) WhenK
p
= 0 orK
p ≥ 6, the O+ ion’s density reaches maximum at longitudes 120° and 240° respectively, and minimum in the magnetotail. WhenK
p
= 3−5, the O+ ion’s density gets to maximum at longitude 0°, and minimum in the magnetotail. However, the O+ ion’s flux reaches maximum at longitude 120° and 240° respectively, and minimum in the magnetotail for anyK
p
value. 相似文献
14.
2022年1月8日,青海省门源县发生MS6.9地震。使用青海、甘肃等区域数字台网所观测到的2009年1月1日—2022年2月8日间青海门源及周边地区(36°～39°N,101°～104°E)14 869次地震事件的地震观测资料,基于双差成像(TomoDD)方法进行重定位分析,结果表明：门源及周边地区地震震源深度较浅,主要集中在5～15 km深度范围,其中10 km附近分布最多。推断该深度区域为门源及周边地区的主要孕震区。基于地震重定位结果和主震区三维速度结构分别对2016年门源MS6.4地震和此次地震序列的发震机理进行分析对比,发现两次地震都位于高速异常体边缘,速度结构与断裂、地震序列吻合较好。2022年门源地震位于高速体的西端末梢位置,是该高速体受青藏高原东北缘顺时针应力作用导致的滑动产生的走滑型地震。 相似文献
15.
"Double low-points" anomaly in daily variation of vertical component of geomagnetic field before the MS8.0 Wenchuan earthquake 
下载免费PDF全文
下载免费PDF全文 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
16.
Rafael Maciel Peña Avto Goguitchaichvili Bernard Henry Leda Sánchez-Bettucci Juan Morales Bertha Aguilar Reyes Ana María Soler-Arechalde Manuel Calvo-Rathert 《Studia Geophysica et Geodaetica》2011,55(2):311-328
The paleosecular variation (PSV) and polarity transitions are two major features of the Earth’s magnetic field. Both PSV and
reversal studies are limited when age of studied units is poorly constrained. This is a case of Central and western Mexico
volcanics. Although many studies have been devoted to these crucial problems and more than 200 paleomagnetic directions are
available for the last 5 Ma, only few sites were dated directly. This paper presents new paleomagnetic results from seventeen
independent cooling units in the Michoacán-Guanajuato Volcanic Field (MGVF) in western Mexico. Twelve sites are directly dated
by 40Ar/39Ar or K-Ar methods and span from 2.78 to 0.56 Ma. The characteristic paleodirections are successfully isolated for 15 lava
flows. The mean paleodirection (inclination I and declination D) obtained in this study is I = 28.8°, D = 354.9°, and Fisherian
statistical parameters are k = 28, α95 = 7.3°, N=15, which corresponds to the mean paleomagnetic pole position Plat = 83.9°, Plong = 321.6°, K = 34, A95 = 6.6°. The paleodirections obtained in present study compiled with those, previously reported from the MGVF, are practically
undistinguishable from the expected Plio-Quaternary paleodirections. The paleosecular variation is estimated through the study
of the scatter of the virtual geomagnetic poles giving SF = 15.9 with SU =21.0 and SL = 12.7 (upper and lower limits respectively). These values agree reasonably well with the recent statistical Models. The
oldest sites analyzed (the Santa Teresa and Cerro Alto) yield normal polarity magnetizations as expected for the cooling units
belonging to the Gauss geomagnetic Chron. The interesting feature of the record comes from lava flows dated at about 2.35
Ma with clearly defined normal directions. This may point out the possible existence of a normal polarity magnetization in
the Matuyama reversed Chron older than the Reunion and may be correlated to Halawa event interpreted as the Cryptochron C2r.2r-1.
Another important feature of the geomagnetic record obtained from the MGVF is the evidence of fully reversed geomagnetic field
within Bruhnes Chron, at about 0.56 Ma corresponding to the relative paleointensity minimum of global extent found in marine
sediments at about 590 ka. 相似文献
17.
Numerous electrodes, already used in geophysics or just perfected by us, have been compared by measuring the three main characteristics which interest the user: noise spectrum, temperature coefficient and polarization with its stability versus time. Among the most used unpolarizable electrodes, silver-silver chloride (Ag-AgCl) are the best ones. But a systematic research of all different possible metal-salt couples, have led us to use lead-lead chloride (Pb-PbCl2) for the following reasons: noise as low as the one of Ag-AgCl at 1 Hz and even lower for the low frequencies (0.4 μV at 1 Hz and 1.2 μV at 0.01 Hz for peak to peak value and ΔF=F), temperature coefficient about ten times weaker (?40 μV/°C instead of ?450 μV/°C) and also better long time stability of the polarization (1 mV/month instead of 2 at 10 mV/month). We have been using these electrodes since 1977 as “tube” electrodes which are very easy to use. They allow us to record correctly the fast variations thanks to their low noise, the very slow variations, their low temperature coefficient and their stability, and this with telluric lines only about 100 m long. 相似文献
18.
O. V. Kozyreva N. G. Kleimenova T. A. Kornilova K. Kauriste J. Manninen A. Ranta 《Geomagnetism and Aeronomy》2006,46(5):580-592
The spatial dynamics of geomagnetic variations and pulsations, auroras, and riometer absorption during the development of the main phase of the extremely strong magnetic storm of November 7–8, 2004, has been studied. It has been indicated that intense disturbances were observed in the early morning sector of auroral latitudes rather than in the nighttime sector, as usually takes place during magnetic storms. The unusual spatial dynamics was revealed at the beginning of the storm main phase. A rapid poleward expansion of disturbances from geomagnetic latitudes of 65°–66° to 74°–75° and the development of the so-called polar cap substorm with a negative bay amplitude of up to 2500 nT, accompanied by precipitation of energetic electrons (riometer absorption) and generation of Pi2–Pi3 pulsations, were observed when IMF B z was about ?45 nT. The geomagnetic activity maximum subsequently sharply shifted equatorward to 60°–61°. The spatial dynamics of the westward electrojet, Pi2–Pi3 geomagnetic pulsations, and riometer absorption was similar, which can indicate that the source of these phenomena is common. 相似文献
19.
《Journal of Atmospheric and Solar》2007,69(15):1833-1841
Results of fractal analysis of ultra-low-frequency (ULF) emissions registered at a low-latitude observatory, Guam (geomagnetic coordinates Φm=9°N, Λm=225°), and at a high-latitude drifting station, North Pole-30 (Φm=75°N, Λm=172°), are presented. The first set of data covers a long period of observations (20 months) including the strong (Ms=8) Guam earthquake of 8 August 1993. The second set of data covers a short period of observations (21 days) in April 1989 during the preparation phase of the big magnetic storm of 25 April 1989. Definite peculiarities in the behavior of ULF emission scaling (fractal) characteristics have been found, which are discussed on the basis of the self-organized criticality concept. The principal common peculiarity for magnetosphere–ionosphere and lithosphere systems is detection of flicker noise (β∼1, D0∼2) in a certain frequency range on the preparation phase of strong magnetospheric and seismic events. 相似文献
20.
V. N. Pogrebnoi V. P. Golovkov T. I. Zvereva E. L. Mozoleva S. Moldobekova 《Geomagnetism and Aeronomy》2010,50(4):536-541
The results of investigations of the latitudinal distribution of annual variation of the geomagnetic field level in the seasons
of 1964 (International Quiet Sun Year) using the data from 95 world magnetic observatories located at various longitudes in
the latitude range 83° N–90° S are reported. The latitudinal features of the X, Y, and Z components of the geomagnetic field have been analyzed. It has been shown that the amplitudes (summer-winter differences)
of the annual variation are maximal in the polar regions, decrease continuously to zero towards the equator, and are identical
for both the Northern and Southern hemispheres with a half-year delay (local summer). The amplitudes of the equinox-winter
difference in the equinox periods are smaller than those in summer, but are manifested simultaneously in the Northern and
Southern hemispheres. An equivalent circumpolar current system has been constructed, which is responsible for the annual variation
of the geomagnetic field level. Its parameters have been determined. 相似文献