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Improved total magnetization direction determination by correlation of the normalized source strength derivative and the reduced-to-pole fields

Zhang Henglei, Dhananjay Ravat, Yara R. Marangoni, Chen Guoxiong and Hu Xiangyun
Improved total magnetization direction determination by correlation of the normalized source strength derivative and the reduced-to-pole fields
Geophysics (December 2018) 83 (6): J75-J85

Abstract

The knowledge of total magnetization (magnitude and direction) makes it easier to interpret magnetic anomalies. We have developed a simple crosscorrelation-based method to determine the total magnetization direction of a magnetic source from the vertical derivative of normalized source strength (dNSS) and the reduced-to-pole (RTP) magnetic fields. For most source types, the spread of the dNSS field (or its half-width) is similar to that of the RTP field computed with the correct total magnetization direction, and, thus, the comparison results in a more meaningful correlation coefficient than other functions used in the literature. We have determined the utility of our method using several compact source types (i.e., sphere, dike, horizontal sheet, vertical and horizontal cylinders, and prism). Moreover, the existing methods for determining the direction can be unstable at low latitudes due to noise amplification. A filter that isolates the main features of the anomaly of interest, when applied to both the fields being correlated, improves the performance of the method. We also implement a stabilizing amplitude threshold filter that made the method stable at low latitudes. Model tests indicate that our method estimates the total magnetization directions accurately for low inclinations of total magnetization and inducing field directions. We applied the method to estimate the total magnetization direction of magnetic anomalies in the north and central part of the Goias Alkaline Province in central Brazil. The RTP fields from the total magnetization directions derived from our method meet the expectations of anomaly symmetry and centering on the outcrops or the edges of the alkaline intrusive bodies. In addition, we found that the resulting magnetic and gravity models of the Goias Alkaline intrusives were consistent with the geologic model of inverted conical diatremes.


ISSN: 0016-8033
EISSN: 1942-2156
Coden: GPYSA7
Serial Title: Geophysics
Serial Volume: 83
Serial Issue: 6
Title: Improved total magnetization direction determination by correlation of the normalized source strength derivative and the reduced-to-pole fields
Affiliation: China University of Geosciences-Wuhan, Institute of Geophysics and Geomatics, Wuhan, China
Pages: J75-J85
Published: 201812
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 39
Accession Number: 2019-010927
Categories: Applied geophysicsIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendices
Illustration Description: illus. incl. 3 tables
S19°30'00" - S12°30'00", W53°19'60" - W46°00'00"
Secondary Affiliation: University of Kentucky, USA, United StatesUniversidade de Sao Paulo, BRA, Brazil
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute.
Update Code: 2019
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