Differential reduction to pole of scalar magnetic anomalies

1987 ◽  
Author(s):  
Jafar Arkani‐Hamed ◽  
David W. Strangway
Keyword(s):  
Magnetic Anomalies ◽  
Differential Reduction

Differential reduction of magnetic anomalies to the pole on a massively parallel computer

Geophysics ◽  
2003 ◽  
Vol 68 (6) ◽  
pp. 1945-1951 ◽  
Author(s):  
Richard S. Lu ◽  
John Mariano ◽  
Dennis E. Willen
Keyword(s):  
Filter Design ◽  
Finite Impulse Response ◽  
Mineral Exploration ◽  
Magnetic Anomalies ◽  
Parallel Computer ◽  
Massively Parallel ◽  
Central Location ◽  
Differential Reduction ◽  
Reduction To The Pole ◽  
The Difference

A finite‐impulse‐response filter was implemented on a computer with massively parallel processors to reduce a magnetic anomaly map to the magnetic pole, allowing each grid node to have a different inclination and declination (differential reduction to the pole, DRTP). The dramatic speed improvement of such an implementation for the filter design and application via space‐domain convolution makes DRTP a practical tool for hydrocarbon and mineral exploration. Application of this tool to magnetic anomalies in east China reveals that the northward shift in position of the anomaly maximum generated by DRTP is 6 km for anomalies with dominant wavelengths of approximately 25 km in the northernmost part of the study area. The shift increases as the anomaly wavelength increases. Shifts for all anomaly wavelengths are even larger in the southern part of the study area, where the magnetic inclination is lower. The shift in position of the anomaly maximum for anomalies of wavelengths 25 km in the northernmost area produced by DRTP is 2 km less than that produced by a conventional reduction to the pole using the inclination and declination at the central location of the study area. Once again, such differences in shifts are larger for anomalies of longer wavelengths. The farther away from the central location, the greater is the absolute value of the difference.

Differential reduction to the pole: Revisited

Geophysics ◽  
2007 ◽  
Vol 72 (1) ◽  
pp. L13-L20 ◽  
Author(s):  
Jafar Arkani-Hamed
Keyword(s):  
Random Noise ◽  
Magnetic Anomalies ◽  
Space Domain ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Domain Reduction ◽  
Low Latitudes ◽  
Differential Reduction ◽  
Low Pass ◽  
Reduction To The Pole

Following a detailed investigation of the Fourier-domain differential reduction-to-the-pole (DRTP) algorithm I compared the results to those obtained using a space-domain reduction-to-the-pole algorithm. I demonstrate that DRTP reduces magnetic anomalies to the pole more effectively than the space-domain algorithm. The DRTP operator has singularities at the geomagnetic equator and enhances north-south trending features at low latitudes. The operator is modified by slightly increasing the inclination of the core field at low latitudes to suppress the singularity. This space-domain modification only affects the anomalies very close to the equator. The modified DRTP operator successfully reduces the magnetic anomalies at low latitudes to the pole. The effects of random noise added to the original magnetic anomalies are investigated in some detail, and an appropriate directional low-pass filter is used to remove the resulting enhanced noise in the reduced-to-the-pole magnetic anomalies. Very simple bodies (uniformly magnetized, cubic, or rectangular) are considered to clearly illustrate the effects of the DRTP, its modified version, and the directional low-pass filter.

Differential reduction‐to‐the‐pole of regional magnetic anomalies

Geophysics ◽  
1988 ◽  
Vol 53 (12) ◽  
pp. 1592-1600 ◽  
Author(s):  
J. Arkani‐Hamed
Keyword(s):  
Frequency Domain ◽  
Regional Scale ◽  
Magnetic Anomalies ◽  
Positive Anomaly ◽  
Low Latitude ◽  
Mean Values ◽  
The North ◽  
Differential Reduction ◽  
Reduction To The Pole ◽  
Spectral Frequency

I present a differential reduction‐to‐the‐pole technique that reduces regional scale magnetic anomalies to the geomagnetic pole, while taking into account the variations in the direction of the geomagnetic field and that of the magnetization of the crust over the region. The technique is developed in the spectral frequency domain as an inverse problem solved iteratively using a perturbation method. I regard the variations in the directions as finite perturbations about the mean values of the directions over the region and evaluate the nonlinear coupling terms due to these perturbations in the space domain at each iteration before transforming them into the spectral frequency domain. The technique is applied to the magnetic anomalies of three semiinfinite prisms, which are inductively magnetized and located at high, mid, and low latitudes in a region where the inclination of the ambient field changes from 10 to 90 degrees and its declination changes from −30 to +30 degrees. The differential reduction to the pole shifts the positive anomaly of the low‐latitude prism toward the north more than it shifts that of the mid‐latitude prism, which in turn is shifted northward more than that of the high‐latitude prism. The reduction also suppresses the negative lobes to the north of the mid and low‐latitude prisms and moves the positive anomalies to points directly over the prisms. I also apply the technique to the marine magnetic anomalies off the east coast of Canada. The positive magnetic anomalies in the southern part of the area are displaced northward by about 30 km, whereas those in the northern part are not moved significantly.

Large magnetic anomalies over Russia revealed by balloon data

2004 ◽  
Vol 6 (6) ◽  
pp. 457-460
Author(s):  
K. A. Nazarova ◽  
T. Sabaka ◽  
Yu. Tsvetkov ◽  
J. Heirtzler
Keyword(s):  
Magnetic Anomalies

Magnetic anomalies, chemical and magnetic properties at wide temperature range (15–1000 K) in LiSrxFe5-xO8 (x = 0, 0.025, 0.05)

2021 ◽  
Vol 859 ◽  
pp. 158290
Author(s):  
S. Udhayakumar ◽  
G. Jagadish Kumar ◽  
E. Senthil Kumar ◽  
M. Navaneethan ◽  
K. Kamala Bharathi
Keyword(s):  
Magnetic Properties ◽  
Wide Temperature Range ◽  
Magnetic Anomalies ◽  
Temperature Range

Metamorphism in the Troodos ophiolite: implications for marine magnetic anomalies

Nature ◽  
1980 ◽  
Vol 285 (5766) ◽  
pp. 563-564 ◽  
Author(s):  
Suzanne Beske-Diehl ◽  
Subir K. Banerjee
Keyword(s):  
Magnetic Anomalies ◽  
Troodos Ophiolite ◽  
Marine Magnetic Anomalies

Large scale magnetic anomalies over western Canada and the Arctic: a discussion

1976 ◽  
Vol 13 (6) ◽  
pp. 790-802 ◽  
Author(s):  
R. L. Coles ◽  
G. V. Haines ◽  
W. Hannaford
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Elevated Temperatures ◽  
Magnetic Anomalies ◽  
The Arctic ◽  
Evolutionary Development ◽  
Magnetic Feature ◽  
Western Canada ◽  
Arctic Regions ◽  
The Magnetic Field

A contoured map of vertical magnetic field residuals (relative to the IGRF) over western Canada and adjacent Arctic regions has been produced by amalgamating new data with those from previous surveys. The measurements were made at altitudes between 3.5 and 5.5 km above sea level. The map shows the form of the magnetic field within the waveband 30 to 5000 km. A magnetic feature of several thousand kilometres wavelength dominates the map, and is probably due in major part to sources in the earth's core. Superimposed on this are several groups of anomalies which contain wavelengths of the order of a thousand kilometres. The patterns of the short wavelength anomalies provide a broad view of major structures and indicate several regimes of distinctive evolutionary development. Enhancement of viscous magnetization at elevated temperatures may account for the concentration of intense anomalies observed near the western edge of the craton.

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