MAGNETIZATION OF PRECAMBRIAN SULPHIDE DEPOSITS AND WALL ROCKS FROM THE NORANDA DISTRICT, CANADA

Geophysics ◽  
1966 ◽  
Vol 31 (4) ◽  
pp. 797-802 ◽  
Author(s):  
E. J. Schwarz
Keyword(s):  
Geomagnetic Field ◽  
Magnetic Anomalies ◽  
Wall Rock ◽  
Average Intensity ◽  
Low Field ◽  
Oriented Samples ◽  
Sulphide Deposits ◽  
The Stability ◽  
Massive Sulphides

Forty‐three oriented samples of massive sulphides, sulphide bearing rocks, quartz porphyries, and diabases were collected in the Quemont and Horne mines. The low‐field susceptibility for the sulphides on the average is somewhat higher than that for both types of wall rocks. The average intensity of the natural remanence of the sulphides is appreciably higher than that of the wall rocks. The ratio of the natural remanence and the induced magnetization (H=0.5 oersteds) is of the order of 1.2 and 0.5 for the sulphides and wall rocks, respectively. The directions of the natural remanence of nearly all samples of sulphide and wall rock are closely parallel to the geomagnetic field. Thus, sulphide bodies of the type studied tend to produce positive magnetic anomalies at the earth’s surface. The stability of the natural remanence of all samples was tested by partial demagnetization in alternating fields. The natural remanence contains a very large unstable component.

scholarly journals Measurements of vector magnetic anomalies on board the icebreaker Shirase and the magnetization of the ship

1999 ◽  
Vol 42 (2) ◽  
Author(s):  
Y. Nogi ◽  
K. Kaminuma
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Magnetic Anomalies ◽  
The Other ◽  
South Indian Ocean ◽  
Permanent Magnetic Field ◽  
South Indian ◽  
Antarctic Research ◽  
Permanent Magnetization ◽  
Made In

Vector measurements of the geomagnetic field have been made in the South Indian Ocean since 1988 when a Shipboard Three Component Magnetometer (STCM) was installed on board the icebreaker Shirase by the 30th Japanese Antarctic Research Expedition (JARE-30). Twelve constants related to the ship's induced and permanent magnetic field were determined by the data obtained from the JARE-30 to the JARE-35. The constants related to the ship's magnetic susceptibility distribution are almost stable throughout the cruise and mostly depend on the ship's shape. On the other hand, the constants related to the ship's permanent magnetization are variable. However, absolute values of total intensity geomagnetic field calculated from vector geomagnetic field is possible to use, if the constraints from total intensity geomagnetic field measured by the proton magnetometer and/or satellite derived magnetic anomalies are applied.

Analysis of Magnetic Anomaly Characteristics of Underground Non-Coplanar Cross-buried Iron Pipelines

2020 ◽  
Vol 25 (2) ◽  
pp. 223-233
Author(s):  
Pan Wu ◽  
Minghui Wei
Keyword(s):  
Magnetic Susceptibility ◽  
Magnetic Anomaly ◽  
Magnetic Dipole ◽  
Geomagnetic Field ◽  
Magnetic Anomalies ◽  
Buried Pipelines ◽  
Magnetic Declination ◽  
Magnetic Inclination ◽  
Basic Characteristics ◽  
Geomagnetic Intensity

The non-coplanar cross-buried pipelines are a common way of pipeline wiring. In order to investigate the magnetic anomaly characteristics of the non-coplanar cross-buried pipelines and guide the site operation, the influences of a series of factors on the magnetic anomaly of the non-coplanar cross-buried pipelines are analyzed. Based on the principle of magnetic dipole construction, a forward model is established for the magnetic anomaly characteristics of the subsurface non-coplanar cross-buried pipelines. The basic characteristics of magnetic anomaly for the non-coplanar cross-buried pipelines are defined. The influences of geomagnetic parameters (geomagnetic intensity, geomagnetic inclination, and geomagnetic declination), pipeline parameters (thickness, magnetic susceptibility), and cross angle of pipelines on the characteristics of magnetic anomalies are analyzed. The results show that the shape of the total magnetic anomaly is mainly affected by the magnetic inclination, and the curve of magnetic anomaly at ± I site shows some symmetry. The amplitude is approximately linearly affected by the total geomagnetic field, magnetic declination, pipeline thickness, material magnetic susceptibility, and pipeline cross angle. There is a periodic change of the amplitude with the increase of geomagnetic inclination (−90°–>90°). The crest-trough distance is mainly affected by geomagnetic inclination, magnetic declination, thickness, magnetic susceptibility, and pipeline cross angle. A more accurate measurement can be achieved if the direction of the pipelines is roughly measured and then the number of measurement points is augmented near the intersection of pipelines and the measurement lines. Present work obtains the equivalent magnetic dipole units by segmenting pipelines. The magnetic anomaly characteristics of non-coplanar crossed iron pipelines are successfully simulated. The numerical results are in accordance with the experimental analysis.

scholarly journals Magnetic anomalies possibly linked to local low seismicity

2009 ◽  
Vol 9 (5) ◽  
pp. 1567-1572 ◽  
Author(s):  
F. Masci ◽  
P. Palangio ◽  
M. Di Persio
Keyword(s):  
Geomagnetic Field ◽  
Central Italy ◽  
Low Frequency ◽  
Magnetic Anomalies ◽  
Tectonic Activity ◽  
The Past ◽  
Tectonic Events ◽  
The City ◽  
Network Station ◽  
The Magnetic Field

Abstract. During the last twenty years a time-synchronized network of magnetometers has operated in Central Italy along the Apennine chain to monitor the magnetic field anomalies eventually related to the tectonic activity. At present time the network consists of five stations. In the past only few anomalies in the local geomagnetic field, possibly associated to earthquakes, has been observed, not least because the network area has shown a low-moderate seismic activity with the epicentres of the few events with Ml≥5 located away from the network station. During 2007 two Ml≈4 earthquakes occurred in proximity of two stations of the network. Here we report the magnetic anomalies in the geomagnetic field that could be related with these tectonic events. To better investigate these two events a study of ULF (ultra-low-frequency) emissions has been carried out on the geomagnetic field components H, D, and Z measured in L'Aquila Observatory during the period from January 2006 to December 2008. We want to stress that this paper refers to the period before the 2009 L'Aquila seismic sequence which main shock (Ml=5.8) of 6 April heavily damaged the medieval centre of the city and surroundings. At present time the analysis of the 2009 data is in progress.

Stability Analysis of Tunnel Surrounding Rock Based on Coupled Fluid-Solid Theory

2011 ◽  
Vol 90-93 ◽  
pp. 1900-1903
Author(s):  
Fu Ming Wang ◽  
Xiao Long Li ◽  
Yan Hui Zhong ◽  
Xiao Guang Chen
Keyword(s):  
Stability Analysis ◽  
Plastic Zone ◽  
Coupling Effect ◽  
Plastic Zone Size ◽  
Wall Rock ◽  
Surrounding Rock ◽  
Maximum Deformation ◽  
Calculation Results ◽  
The Stability ◽  
Tunnel Depth

Taking Chaijiazhuang Tunnel of Lingnan Expressway as project background, the stability analysis of surrounding rock was performed based on the coupled fluid-solid theory. The distributions of stress field, displacement field and plastic zone of rock mass after excavation of tunnel were discussed considering coupled effect between flow and stress under the condition of different rock level and tunnel depth. Compared with the calculation results of not considering coupling effect, the maximum deformation, maximum principle stress and plastic zone size of wall rock were obviously increased when considering coupling effect, which showed a remarkable influence of coupled fluid-solid effect on the stability of tunnel surrounding rock. Some conclusions were drawn and may provide some guidance to the design and construction of tunnels in water-rich strata.

scholarly journals Experimental Study on the Localization of Moving Object by Total Geomagnetic Field

2017 ◽  
Vol 2017 ◽  
pp. 1-7
Author(s):  
Chong Kang ◽  
Liming Fan ◽  
Quan Zheng ◽  
Xiyuan Kang ◽  
Jian Zhou ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
High Sensitivity ◽  
Magnetic Anomalies ◽  
Target Localization ◽  
Total Field ◽  
Detection Range ◽  
Vector Sensors ◽  
Field Localization ◽  
Low Sensitivity

In the method of target localization based on magnetic anomalies, the scheme of vector field localization and experimental research are significant. Because more information of magnetic field can be measured by vector sensors, the position of the target can be directly calculated by the equations. However, the vector magnetic anomaly generated by the target is difficult to measure. And the detection range is small due to the low sensitivity of vector sensors. A method for target localization based on the total geomagnetic field is proposed. Its advantages are that the measurement of total magnetic field is not affected by the orientation of the total field sensors and the detection range is large due to their high sensitivity. In this paper, we focus on the localization using the array with the total field magnetometers. And we design an array structure with the total field magnetometers. Then, we obtain the higher order nonlinear equations for the target localization based on this array. The numerical method is used to solve the equations. Meanwhile, we present a method for eliminating the effect of geomagnetic field variations and uneven spatial distribution. In suburban roads, localization experiments were carried out. And the results showed that the relative error of target localization is less than 5% by using the proposed method.

Marine magnetic anomalies, geomagnetic field reversals, and motions of the ocean floor and continents

1968 ◽  
Vol 73 (6) ◽  
pp. 2119-2136 ◽  
Author(s):  
J. R. Heirtzler ◽  
G. O. Dickson ◽  
E. M. Herron ◽  
W. C. Pitman ◽  
X. Le Pichon
Keyword(s):  
Geomagnetic Field ◽  
Magnetic Anomalies ◽  
Ocean Floor ◽  
Marine Magnetic Anomalies

scholarly journals AS FOLLOWS FROM OUR MODEL THE NORTH MAGNETIC POLE IS STABLE IN ITS DRIFT

2019 ◽  
pp. 65-76
Author(s):  
B.В. Кузнецов
Keyword(s):  
Geomagnetic Field ◽  
Magnetic Anomalies ◽  
Magnetic Pole ◽  
The West ◽  
The North ◽  
Drift Model ◽  
North Magnetic Pole ◽  
Resolute Bay ◽  
Magnetic Observatories

Северный магнитный полюс движется согласно модели дрейфа, предложенной канадским магнитологом Хоупом 1 и разработанной автором этой статьи 2, 3. В основе модели участие двух глобальных магнитных аномалий (ГМА): Канадской (КМА) и Сибирской (СМА). Вблизи этих ГМА расположены магнитные обсерватории: РезольютБей (RB Resolute Bay) в Канаде и Мыс Челюскин (CCh Cape Chelyskin) в России. Обсерватории регистрируют изменения величин Нкомпонент модуля геомагнитного поля (ГМП), причем в настоящее время в Канадском секторе регистрируется увеличение модуля ГМП, а в Сибирском, его уменьшение. Точка, в которой направленные навстречу векторы Нкомпонент равны друг другу, а Нкомпонента равна нулю, и есть СМП. Скорость дрейфа СМП определяется скоростью увеличения (или уменьшения) величин соответствующих ГМА. Использование этой простейшей схемы позволило автору давать очень точные прогнозы мест расположения СМП. Точно так же было определено время перехода СМП из Западного полушария в Восточное (лето 2019). Точность методики определяется исключительно точностью аппроксимации величины Нкомпонент 24. The North Magnetic Pole submits its moving to the drift model proposed by Canadian magnitologist Hope 5 and this developed by the author 6,7 which suggests an impact of two global magnetic anomalies (GMA), Canadian (CMA) and Siberian (SMA) into the pole drift. Magnetic observatories Resolute Bay, Canada, and Cape Chelyskin, Russia, located near these GMA, are recording the Hcomponent values. Nowadays increasing at the Canada area the geomagnetic field module is decreasing at the Siberia one. The NMP is the point where the vectors of Hcomponent directed towards each other are equal and the value of Hcomponent makes zero. The velocity of the NMP drift is determined by the fluctuating rate of GMA magnitudes. This technique enabled the author to predict as the NMP positions and the time of the NMP transit from the West hemisphere to the East one as 2019, summer. The technique accuracy is governed by accuracy of Hcomponent values approximation 6, 7, 13.

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