The automatic determination of the location, depth, and dip of contacts from aeromagnetic data

Geophysics ◽  
2014 ◽  
Vol 79 (3) ◽  
pp. J35-J41 ◽  
Author(s):  
Gordon R. J. Cooper
Keyword(s):  
Magnetic Field ◽  
Tilt Angle ◽  
Synthetic Data ◽  
Magnetic Data ◽  
Aeromagnetic Data ◽  
Third Order ◽  
Contour Lines ◽  
Derivatives Of ◽  
The Magnetic Field

A simple new method (termed the contact-depth method) for the determination of the depth, location, and dip of contacts from pole reduced magnetic data was evaluated. The depth was obtained by computing the horizontal derivative of the tangent of the tilt angle of the magnetic field over the contact. Although it is based upon the tilt-depth method, it does not require the distance between contour lines to be measured, and it additionally allows the dip of the contact to be estimated from the gradient of the depth estimates. The horizontal location of the contact is that of the zero value of the tilt angle. The method uses second- and third-order derivatives of the magnetic field to obtain the parameters of the contact, so it is sensitive to noise. When tested on synthetic data and on aeromagnetic data from southern Africa, the method gave plausible results.

Kinetic and transport theory for a non-neutral plasma taking account of strong gyration and non-uniformities on the collisional scale

1987 ◽  
Vol 38 (3) ◽  
pp. 351-371 ◽  
Author(s):  
Alf H. Øien
Keyword(s):  
Magnetic Field ◽  
Distribution Function ◽  
Electric Field ◽  
Strong Magnetic Field ◽  
Transport Theory ◽  
Collision Integral ◽  
Collision Term ◽  
Third Order ◽  
Derivatives Of ◽  
The Magnetic Field

From the BBGKY equations for a pure electron plasma a derivation is made of a collision integral that includes the combined effects of particle gyration in a strong magnetic field and non-uniformities of both the distribution function and the self-consistent electric field on the collisional scale. A series expansion of the collision integral through the distribution function and the electric field on the collisional scale is carried out to third order in derivatives of the distribution function and to second order in derivatives of the electric field. For the strong-magnetic-field case when collision-term contributions to only first order in 1/B are included, a particle flux transverse to the magnetic field proportional to l/B2 is derived. The importance of long-range collective collisions in this process is shown. The result is in contrast with the classical l/B4 proportionality, and is in accordance with earlier studies.

Automatic boundary extraction from magnetic field data using triangular meshes

Geophysics ◽  
2016 ◽  
Vol 81 (3) ◽  
pp. J47-J60 ◽  
Author(s):  
Nathan Leon Foks ◽  
Yaoguo Li
Keyword(s):  
Magnetic Field ◽  
Synthetic Data ◽  
Magnetic Data ◽  
Lake Area ◽  
Boundary Extraction ◽  
Data Set ◽  
Magnetic Field Data ◽  
Line Segments ◽  
Extraction Algorithm ◽  
The Magnetic Field

Boundary extraction is a collective term that we use for the process of extracting the locations of faults, lineaments, and lateral boundaries between geologic units using geophysical observations, such as measurements of the magnetic field. The process typically begins with a preprocessing stage, where the data are transformed to enhance the visual clarity of pertinent features and hence improve the interpretability of the data. The majority of the existing methods are based on raster grid enhancement techniques, and the boundaries are extracted as a series of points or line segments. In contrast, we set out a methodology for boundary extraction from magnetic data, in which we represent the transformed data as a surface in 3D using a mesh of triangular facets. After initializing the mesh, we modify the node locations, such that the mesh smoothly represents the transformed data and that facet edges are aligned with features in the data that approximate the horizontal locations of subsurface boundaries. To illustrate our boundary extraction algorithm, we first apply it to a synthetic data set. We then apply it to identify boundaries in a magnetic data set from the McFaulds Lake area in Ontario, Canada. The extracted boundaries are in agreement with known boundaries and several of the regions that are completely enclosed by extracted boundaries coincide with regions of known mineralization.

An assessment of long-wavelength magnetic anomalies over Canada

1996 ◽  
Vol 33 (1) ◽  
pp. 12-23 ◽  
Author(s):  
Mark Pilkington ◽  
Walter R. Roest
Keyword(s):  
Magnetic Field ◽  
Magnetic Anomalies ◽  
Time Span ◽  
Magnetic Data ◽  
Data Sets ◽  
Independent Data ◽  
Data Set ◽  
Long Wavelength ◽  
The Magnetic Field

The reliability of the long-wavelength portion (> 300 km) of the magnetic field over Canada, as represented by the national aeromagnetic anomaly database compiled by the Geological Survey of Canada (GSC), is assessed by comparison with two independent data sets: a high-altitude country-wide survey carried out by the former Earth Physics Branch (EPB) and data from the MAGSAT and POGO satellite missions. The different altitudes at which each data set was measured (300 m, ~4 km, and ~400 km), and their different resolution and time span of observations allow a determination of the integrity of selected wavelength bands in each data set. The (upward-continued) EPB and MAGSAT–POGO fields compare well for wavelengths of 300–2500 km. The GSC data show significant differences to the former, indicating that the levelling and merging of several hundred individual surveys has degraded the longer wavelength components of the magnetic field. Replacing the GSC wavelength components >300 km with those from the EPB field produces a magnetic data set containing more dependable information within the largest possible waveband.

Zum Rotations-Zeeman-Effekt in Dimethylketen / Molecular Zeeman Effect and the Determination of the Molecular g Values, Paramagnetic Susceptibilities, and Molecular Quadrupole Moments in Dimethylketene

1972 ◽  
Vol 27 (4) ◽  
pp. 597-600 ◽  
Author(s):  
D. Sutter ◽  
L. Charpentier ◽  
H. Dreizler
Keyword(s):  
Magnetic Field ◽  
Zeeman Effect ◽  
Microwave Spectrum ◽  
Quadrupole Moments ◽  
Selection Rules ◽  
Rotational Transitions ◽  
The Magnetic Field

Abstract The rotational Zeeman-Effect in the microwave spectrum of dimethylketene was investigated at fieldstrengths close to 22 kG. Only ΔJ= 1 rotational transitions with ΔM = ± 1 selection rules did show appreciable splittings due to the magnetic field. From the splittings the diagonal elements of the molecular gr-tensor were determined to be: gaa = ∓ 0.020(3) ; gbb = ∓ 0.0165(8) ; gcc= + 0.0126(5). (Only the relative signs of the g-values are obtained from the experiment). The susceptibility anisotropics were found to be close to zero.

Determination of the spatial length scale of the magnetic field distribution in YBa2Cu3O7 ceramics and Bi2Sr2CaCu2O8 crystal

1991 ◽  
Vol 185-189 ◽  
pp. 1809-1810 ◽  
Author(s):  
N. Bontemps ◽  
P.Y. Bertin ◽  
D. Davidov ◽  
P. Monod ◽  
C. Lacour ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Distribution ◽  
Magnetic Field Distribution ◽  
Length Scale ◽  
The Magnetic Field

scholarly journals Determination of the Complete Penetration Magnetic Field of a HTS Pellet From the Measurements of the Magnetic Field at Its Top-Center Surface

2018 ◽  
Vol 28 (4) ◽  
pp. 1-4
Author(s):  
Bruno Douine ◽  
Kevin Berger ◽  
Frederic Trillaud ◽  
Mohamed Elbaa ◽  
El Hadj Ailam
Keyword(s):  
Magnetic Field ◽  
The Magnetic Field
Sign in / Sign up

Export Citation Format

Share Document