Fusion of gravity gradient and magnetic field data for discrimination of anomalies using deformation analysis

Gravity gradiometry and magnetometry methods are powerful noninvasive techniques for near-surface detection problems. Efficient integration of data from these techniques decreases the degree of nonuniqueness in geophysical interpretations. Deformation analysis is a powerful tool for comparison of two fields, which aids in this respect. We propose a fully quantitative approach, which uses the generalized theory of deformation for the geometric comparison of gravimetric and magnetic fields. The resulting deformation maps delineate regions where Poisson’s relation is violated between the two data sets and thus discriminate between air-filled cavities and other similar low-density/susceptibility geophysical sources. We present a practical corresponding algorithm that is robust in the sense that no prior knowledge of the physical properties of the subsurface is needed.

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Exploration of solar photospheric magnetic field data sets using the UCSD tomography

Space Weather ◽

10.1002/2016sw001481 ◽

2016 ◽

Vol 14 (12) ◽

pp. 1107-1124 ◽

Cited By ~ 6

Author(s):

B. V. Jackson ◽

H.-S. Yu ◽

A. Buffington ◽

P. P. Hick ◽

N. Nishimura ◽

...

Keyword(s):

Magnetic Field ◽

Field Data ◽

Photospheric Magnetic Field ◽

Data Sets ◽

Magnetic Field Data

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Interpretation of aeromagnetic data using eigenvector analysis of pseudogravity gradient tensor

Geophysics ◽

10.1190/1.3555343 ◽

2011 ◽

Vol 76 (3) ◽

pp. L1-L10 ◽

Cited By ~ 17

Author(s):

Majid Beiki ◽

Laust B. Pedersen ◽

Hediyeh Nazi

Keyword(s):

Magnetic Field ◽

Least Squares ◽

Field Data ◽

Random Noise ◽

Gravity Gradient ◽

Aeromagnetic Data ◽

Gradient Tensor ◽

Magnetization Direction ◽

Magnetic Field Data ◽

Robust Least Squares

This study has shown that the same properties of the gravity gradient tensor are valid for the pseudogravity gradient tensor derived from magnetic field data, assuming that the magnetization direction is known. Eigenvectors of the pseudogravity gradient tensor are used to estimate depth to the center of mass of geologic bodies. The strike directions of 2D geological structures are estimated from the eigenvectors corresponding to the smallest eigenvalues. For a set of data points enclosed by a square window, a robust least-squares procedure is used to estimate the source point which has the smallest sum of squared distances to the lines passing through the measurement points and parallel to the eigenvectors corresponding to the maximum eigenvalues. The dimensionality of the pseudogravity field is defined from the dimensionality indicator I, derived from the tensor components. In the case of quasi-2D sources, a rectangular window is used in the robust least-squares procedure to reduce the uncertainty of estimations.Based on synthetic data sets, the method was tested on synthetic models and found to be robust to random noise in magnetic field data. The application of the method was also tested on a pseudogravity gradient tensor derived from total magnetic field data over the Särna area in west-central Sweden. Combined with Euler deconvolution, the method provides useful complementary information for interpretation of aeromagnetic data.

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Timing of the martian dynamo: New constraints for a core field 4.5 and 3.7 Ga ago

Science Advances ◽

10.1126/sciadv.aba0513 ◽

2020 ◽

Vol 6 (18) ◽

pp. eaba0513 ◽

Cited By ~ 3

Author(s):

A. Mittelholz ◽

C. L. Johnson ◽

J. M. Feinberg ◽

B. Langlais ◽

R. J. Phillips

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Field Data ◽

Magnetic Minerals ◽

Near Surface ◽

Magnetic Field Data ◽

Core Field ◽

Before And After ◽

Basin Edge ◽

Weak Fields

The absence of crustal magnetic fields above the martian basins Hellas, Argyre, and Isidis is often interpreted as proof of an early, before 4.1 billion years (Ga) ago, or late, after 3.9 Ga ago, dynamo. We revisit these interpretations using new MAVEN magnetic field data. Weak fields are present over the 4.5-Ga old Borealis basin, with the transition to strong fields correlated with the basin edge. Magnetic fields, confined to a near-surface layer, are also detected above the 3.7-Ga old Lucus Planum. We conclude that a dynamo was present both before and after the formation of the basins Hellas, Utopia, Argyre, and Isidis. A long-lived, Earth-like dynamo is consistent with the absence of magnetization within large basins if the impacts excavated large portions of strongly magnetic crust and exposed deeper material with lower concentrations of magnetic minerals.

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Characteristics of the Taylor microscale in the solar wind/foreshock: magnetic field and electron velocity measurements

Annales Geophysicae ◽

10.5194/angeo-31-2063-2013 ◽

2013 ◽

Vol 31 (11) ◽

pp. 2063-2075 ◽

Cited By ~ 2

Author(s):

C. Gurgiolo ◽

M. L. Goldstein ◽

W. H. Matthaeus ◽

A. Viñas ◽

A. N. Fazakerley

Keyword(s):

Magnetic Field ◽

Field Data ◽

Fluid Velocity ◽

Electron Velocity ◽

Data Sets ◽

Velocity Data ◽

Data Set ◽

Magnetic Field Data ◽

Spacecraft Data ◽

The Magnetic Field

Abstract. The Taylor microscale is one of the fundamental turbulence scales. Not easily estimated in the interplanetary medium employing single spacecraft data, it has generally been studied through two point correlations. In this paper we present an alternative, albeit mathematically equivalent, method for estimating the Taylor microscale (λT). We make two independent determinations employing multi-spacecraft data sets from the Cluster mission, one using magnetic field data and a second using electron velocity data. Our results using the magnetic field data set yields a scale length of 1538 ± 550 km, slightly less than, but within the same range as, values found in previous magnetic-field-based studies. During time periods where both magnetic field and electron velocity data can be used, the two values can be compared. Relative comparisons show λT computed from the velocity is often significantly smaller than that from the magnetic field data. Due to a lack of events where both measurements are available, the absolute λT based on the electron fluid velocity is not able to be determined.

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

Journal of Geological Research ◽

10.30564/jgr.v1i3.1316 ◽

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.

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

Geophysical Research Letters ◽

10.1029/98gl02802 ◽

1998 ◽

Vol 25 (19) ◽

pp. 3721-3724 ◽

Cited By ~ 3

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

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Ogo 5 magnetic-field data near the Earth's bow shock: A correlation with theory

Journal of Geophysical Research Atmospheres ◽

10.1029/ja077i004p00604 ◽

1972 ◽

Vol 77 (4) ◽

pp. 604-610 ◽

Cited By ~ 19

Author(s):

J. K. Guha ◽

D. L. Judge ◽

J. H. Marburger

Keyword(s):

Magnetic Field ◽

Field Data ◽

Bow Shock ◽

Magnetic Field Data ◽

Earth’S Bow Shock

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Using an induction coil sensor to indirectly measure the B-field response in the bandwidth of the transient electromagnetic method

Geophysics ◽

10.1190/1.1444837 ◽

2000 ◽

Vol 65 (5) ◽

pp. 1489-1494 ◽

Cited By ~ 34

Author(s):

Richard S. Smith ◽

A. Peter Annan

Keyword(s):

Magnetic Field ◽

Field Data ◽

Indirect Measurement ◽

Rate Of Change ◽

Induction Coil ◽

Voltage Response ◽

Magnetic Field Data ◽

Transient Electromagnetic ◽

Different Characteristics ◽

The Magnetic Field

The traditional sensor used in transient electromagnetic (EM) systems is an induction coil. This sensor measures a voltage response proportional to the time rate of change of the magnetic field in the EM bandwidth. By simply integrating the digitized output voltage from the induction coil, it is possible to obtain an indirect measurement of the magnetic field in the same bandwidth. The simple integration methodology is validated by showing that there is good agreement between synthetic voltage data integrated to a magnetic field and synthetic magnetic‐field data calculated directly. Further experimental work compares induction‐coil magnetic‐field data collected along a profile with data measured using a SQUID magnetometer. These two electromagnetic profiles look similar, and a comparison of the decay curves at a critical point on the profile shows that the two types of measurements agree within the bounds of experimental error. Comparison of measured voltage and magnetic‐field data show that the two sets of profiles have quite different characteristics. The magnetic‐field data is better for identifying, discriminating, and interpreting good conductors, while suppressing the less conductive targets. An induction coil is therefore a suitable sensor for the indirect collection of EM magnetic‐field data.

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