THE USE OF POISSON’S RELATION FOR THE EXTRACTION OF PSEUDOTOTAL MAGNETIC FIELD INTENSITY FROM GRAVITY OBSERVATIONS

Geophysics ◽  
1971 ◽  
Vol 36 (3) ◽  
pp. 605-608 ◽  
Author(s):  
Edwin S. Robinson
Keyword(s):  
Magnetic Field ◽  
Gravity Field ◽  
Field Data ◽  
Field Potential ◽  
Geological Structure ◽  
Common Source ◽  
Uniform Density ◽  
Practical Applications ◽  
Uniform Magnetization ◽  
Gravity Fields

Investigation of geological structure by gravimetric and magnetic field surveys requires consideration of relationships between gravity anomaly and magnetic anomaly generating sources. The possibility of using Poisson’s Relation to examine magnetic and gravity fields related to a common source is intriguing. This relation is expressed as follows: [Formula: see text] (1) where A (x, y, z) is the magnetic field potential and U (x, y, z) is the gravity field potential at a point in space due to a source of uniform density ρ and uniform magnetization I in the direction α. This expression has been used to derive magnetic anomalies over idealized forms (Nettleton, 1940) and, by Baranov (1957), to extract pseudogravity fields from magnetic field data. The purpose of this paper is to develop an expression for extracting a pseudomagnetic field from gravity field data and to examine the practical applications of this expression.

Interactive gravity inversion

Geophysics ◽  
2006 ◽  
Vol 71 (1) ◽  
pp. J1-J9 ◽  
Author(s):  
João B. C. Silva ◽  
Valéria C. F. Barbosa
Keyword(s):  
Gravity Field ◽  
Field Data ◽  
Synthetic Data ◽  
The Other ◽  
Density Contrast ◽  
Gravity Inversion ◽  
Homogeneous Body ◽  
New Approach ◽  
Line Segments ◽  
Gravity Fields

We have developed a new approach for estimating the location and geometry of several density anomalies that give rise to a complex, interfering gravity field. The user interactively defines the assumed outline of the true gravity sources in terms of points and line segments, and the method estimates sources closest to the specified outline to achieve a match between the predicted and observed gravity fields. Each gravity source is assumed to be a homogeneous body with a known density contrast; different density contrasts may be assigned to each source. Tests with synthetic data show that the method can be of use in estimating (1) multiple laterally adjacent and closely situated gravity sources, (2) single gravity sources consisting of several homogeneous compartments with different density contrasts, and (3) two gravity sources with different density contrasts of the same sign, one totally enclosed by the other. The method is also applied to three different sets of field data where the gravity sources belong to the same categories established in the tests with synthetic data. The method produces solutions consistent with the known geologic attributes of the gravity sources, illustrating its potential practicality.

scholarly journals CHARACTERISTICS OF GEOPHYSICAL FIELDS ON THE ELBRUS AND KAZBEK

2014 ◽  
Author(s):  
В.Б. Заалишвили ◽  
Н.И. Невская ◽  
Л.Н. Невский ◽  
А.Г. Шемпелев
Keyword(s):  
Magnetic Field ◽  
Surface Layer ◽  
Geological Structure ◽  
Regional Level ◽  
The Caucasus ◽  
Caucasus Region ◽  
Gravity Fields ◽  
Central Caucasus ◽  
Local Anomalies ◽  
The Magnetic Field

В статье рассмотрены особенности геологического строения Эльбруса и Казбека. Одной из особен- ностей поля силы тяжести Кавказа является наличие для районов Приэльбрусья и Чегемского нагорья самых минимальных значений в Большекавказском регионе. Относительно положительные значения гра- витационного поля Казбекского района, определяются приповерхностным слоем с избыточной плотно- стью 0,15х103 кгм3 верхняя и нижняя границы которого находятся на глубинах порядка 0,5 и 4,5 км. Зона Главного хребта Центрального Кавказа является в региональном плане областью пониженных значений магнитного поля, которое осложнено локальными знакопеременными аномалиями. In the article the features of geological structure of Elbrus and Kazbek are examined. One of the features of the gravity fields of the Caucasus is the availability for areas of Elbrus and Chegem Highlands most minimum values in the big Caucasus region. The positive values of the gravitational field of the Kazbek district, are determined by the surface layer with excessive densities of 0,15х103 кgм3 the top and bottom borders are at depths of about 0.5 and 4.5 km. Area of the main ridge of the Central Caucasus has at the regional level the lower values of the magnetic field, which is complicated by alternating local anomalies

Numerical Calculation of Non-uniform Magnetization Using Experimental Magnetic Field Data

2018 ◽  
Vol 72 (9) ◽  
pp. 1058-1062
Author(s):  
Bukyoung Jhun ◽  
Youngseok Jhun ◽  
Seung-wook Kim ◽  
JungHyun Han
Keyword(s):  
Magnetic Field ◽  
Numerical Calculation ◽  
Field Data ◽  
Magnetic Field Data ◽  
Uniform Magnetization

An Augmented Iteratively Re-weighted and Refined Least Squares Method for lp Minimization Problem in Inverse Modeling of Potential Field Magnetic Data

2020 ◽  
Vol 1 (3) ◽  
Author(s):  
Maysam Abedi
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Least Squares ◽  
Minimization Problem ◽  
Potential Field ◽  
Field Data ◽  
Least Squares Method ◽  
Porphyry Copper ◽  
Magnetic Data ◽  
Magnetic Field Data

The presented work examines application of an Augmented Iteratively Re-weighted and Refined Least Squares method (AIRRLS) to construct a 3D magnetic susceptibility property from potential field magnetic anomalies. This algorithm replaces an lp minimization problem by a sequence of weighted linear systems in which the retrieved magnetic susceptibility model is successively converged to an optimum solution, while the regularization parameter is the stopping iteration numbers. To avoid the natural tendency of causative magnetic sources to concentrate at shallow depth, a prior depth weighting function is incorporated in the original formulation of the objective function. The speed of lp minimization problem is increased by inserting a pre-conditioner conjugate gradient method (PCCG) to solve the central system of equation in cases of large scale magnetic field data. It is assumed that there is no remanent magnetization since this study focuses on inversion of a geological structure with low magnetic susceptibility property. The method is applied on a multi-source noise-corrupted synthetic magnetic field data to demonstrate its suitability for 3D inversion, and then is applied to a real data pertaining to a geologically plausible porphyry copper unit.  The real case study located in  Semnan province of  Iran  consists  of  an arc-shaped  porphyry  andesite  covered  by  sedimentary  units  which  may  have  potential  of  mineral  occurrences, especially  porphyry copper. It is demonstrated that such structure extends down at depth, and consequently exploratory drilling is highly recommended for acquiring more pieces of information about its potential for ore-bearing mineralization.

scholarly journals Integral Equations for Problems on Wave Propagation in Near-Earth Plasma

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1395
Author(s):  
Danila Kostarev ◽  
Dmitri Klimushkin ◽  
Pavel Mager
Keyword(s):  
Magnetic Field ◽  
Integral Equations ◽  
Field Potential ◽  
Low Frequency ◽  
Fredholm Equation ◽  
Compression Waves ◽  
Parallel Component ◽  
Electric Field Potential ◽  
The Magnetic Field ◽  
Low Frequency Waves

We consider the solutions of two integrodifferential equations in this work. These equations describe the ultra-low frequency waves in the dipol-like model of the magnetosphere in the gyrokinetic framework. The first one is reduced to the homogeneous, second kind Fredholm equation. This equation describes the structure of the parallel component of the magnetic field of drift-compression waves along the Earth’s magnetic field. The second equation is reduced to the inhomogeneous, second kind Fredholm equation. This equation describes the field-aligned structure of the parallel electric field potential of Alfvén waves. Both integral equations are solved numerically.

scholarly journals A reexamination of “interstellar ion waves” previously identified in Pioneer 10 magnetic field data

1998 ◽  
Vol 25 (19) ◽  
pp. 3721-3724 ◽  
Author(s):  
Neil Murphy ◽  
Edward J. Smith ◽  
Joyce Wolf ◽  
Devrie S. Intriligator
Keyword(s):  
Magnetic Field ◽  
Field Data ◽  
Magnetic Field Data ◽  
Ion Waves ◽  
Pioneer 10

Combining the deep Earth and lithospheric gravity field to study the density structure of the upper mantle

2021 ◽  
Author(s):  
Bart Root ◽  
Javier Fullea ◽  
Jörg Ebbing ◽  
Zdenek Martinec
Keyword(s):  
Gravity Field ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Field Data ◽  
Wavelength Region ◽  
Density Structure ◽  
Long Wavelength ◽  
Global Gravity ◽  
Deep Earth

<p>Global gravity field data obtained by dedicated satellite missions is used to study the density distribution of the lithosphere. Different multi-data joint inversions are using this dataset together with other geophysical data to determine the physical characteristics of the lithosphere. The gravitational signal from the deep Earth is usually removed by high-pass filtering of the model and data, or by appropriately selecting insensitive gravity components in the inversion. However, this will remove any long-wavelength signal inherent to lithosphere. A clear choice on the best-suited approach to remove the sub-lithospheric gravity signal is missing. </p><p>Another alternative is to forward model the gravitational signal of these deep situated mass anomalies and subtract it from the observed data, before the inversion. Global tomography provides shear-wave velocity distribution of the mantle, which can be transformed into density anomalies. There are difficulties in constructing a density model from this data. Tomography relies on regularisation which smoothens the image of the mantle anomalies. Also, the shear-wave anomalies need to be converted to density anomalies, with uncertain conversion factors related to temperature and composition. Understanding the sensitivity of these effects could help determining the interaction of the deep Earth and the lithosphere.</p><p>In our study the density anomalies of the mantle, as well as the effect of CMB undulations, are forward modelled into their gravitational potential field, such that they can be subtracted from gravity observations. The reduction in magnitude of the density anomalies due to the regularisation of the global tomography models is taken into account. The long-wavelength region of the density estimates is less affected by the regularisation and can be used to fix the mean conversion factor to transform shear wave velocity to density. We present different modelling approaches to add the remaining dynamic topography effect in lithosphere models. This results in new solutions of the density structure of the lithosphere that both explain seismic observations and gravimetric measurements. The introduction of these dynamic forces is a step forward in understanding how to properly use global gravity field data in joint inversions of lithosphere models.</p>

scholarly journals Tunable Adhesion of a Bio-Inspired Micropillar Arrayed Surface Actuated by a Magnetic Field

2018 ◽  
Vol 86 (1) ◽  
Author(s):  
Xingji Li ◽  
Zhilong Peng ◽  
Yazheng Yang ◽  
Shaohua Chen
Keyword(s):  
Magnetic Field ◽  
Applied Magnetic Field ◽  
Magnetic Particles ◽  
Rotation Angle ◽  
Adhesion Force ◽  
Practical Applications ◽  
Section Shape ◽  
Theoretical Predictions ◽  
Large Elastic Deformation ◽  
The Difference

Bio-inspired functional surfaces attract many research interests due to the promising applications. In this paper, tunable adhesion of a bio-inspired micropillar arrayed surface actuated by a magnetic field is investigated theoretically in order to disclose the mechanical mechanism of changeable adhesion and the influencing factors. Each polydimethylsiloxane (PDMS) micropillar reinforced by uniformly distributed magnetic particles is assumed to be a cantilever beam. The beam's large elastic deformation is obtained under an externally magnetic field. Specially, the rotation angle of the pillar's end is predicted, which shows an essential effect on the changeable adhesion of the micropillar arrayed surface. The larger the strength of the applied magnetic field, the larger the rotation angle of the pillar's end will be, yielding a decreasing adhesion force of the micropillar arrayed surface. The difference of adhesion force tuned by the applied magnetic field can be a few orders of magnitude, which leads to controllable adhesion of such a micropillar arrayed surface. Influences of each pillar's cross section shape, size, intervals between neighboring pillars, and the distribution pattern on the adhesion force are further analyzed. The theoretical predictions are qualitatively well consistent with the experimental measurements. The present theoretical results should be helpful not only for the understanding of mechanical mechanism of tunable adhesion of micropillar arrayed surface under a magnetic field but also for further precise and optimal design of such an adhesion-controllable bio-inspired surface in future practical applications.

scholarly journals The importance of entrainment and bulking on debris flow runout modeling: examples from the Swiss Alps

2015 ◽  
Vol 15 (11) ◽  
pp. 2569-2583 ◽  
Author(s):  
F. Frank ◽  
B. W. McArdell ◽  
C. Huggel ◽  
A. Vieli
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Field Data ◽  
Average Rate ◽  
Hazard Analysis ◽  
Maximum Shear Stress ◽  
Empirical Relationship ◽  
Swiss Alps ◽  
Field Site ◽  
Practical Applications

Abstract. This study describes an investigation of channel-bed entrainment of sediment by debris flows. An entrainment model, developed using field data from debris flows at the Illgraben catchment, Switzerland, was incorporated into the existing RAMMS debris-flow model, which solves the 2-D shallow-water equations for granular flows. In the entrainment model, an empirical relationship between maximum shear stress and measured erosion is used to determine the maximum potential erosion depth. Additionally, the average rate of erosion, measured at the same field site, is used to constrain the erosion rate. The model predicts plausible erosion values in comparison with field data from highly erosive debris flow events at the Spreitgraben torrent channel, Switzerland in 2010, without any adjustment to the coefficients in the entrainment model. We find that by including bulking due to entrainment (e.g., by channel erosion) in runout models a more realistic flow pattern is produced than in simulations where entrainment is not included. In detail, simulations without entrainment show more lateral outflow from the channel where it has not been observed in the field. Therefore the entrainment model may be especially useful for practical applications such as hazard analysis and mapping, as well as scientific case studies of erosive debris flows.

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