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TitlePractical considerations in the use of edge detectors for geological mapping using magnetic data
AuthorPilkington, M; Tschirhart, V
SourceGeophysics vol. 82, (2017), no. 3, 2017.,
Alt SeriesEarth Sciences Sector, Contribution Series 20160325
PublisherSociety of Exploration Geophysicists
Mediapaper; on-line; digital
File formatpdf
Subjectsgeophysics; magnetic field; magnetic field intensity; magnetic interpretations; magnetic surveys; magnetic surveys, airborne; total field magnetics; magnetic inclination; electromagnetic mapping; mapping techniques; magnetization
Illustrationsgraphs; schematic diagrams; formulae; location maps; stratigraphic columns; geological sketch maps; magnetic anomaly maps; magnetic maps
ProgramRae Province, Chantrey-Thelon, GEM2: Geo-mapping for Energy and Minerals
AbstractMuch effort has been expended on developing improvements to existing edge detection methods, resulting in purported increases in accuracy and continuity along edges, reduction in noise effects, and limiting the influences of variable depth to source, magnetization direction, and source dip. These endeavours are valuable and provide interpreters with a wider range of tools to carry out geological interpretations of geophysical data. Nevertheless, geological field mapping practises and aeromagnetic survey parameters (height and line spacing) impose limits on the quality of edge detectors necessary to provide the appropriate level of information used construct a geological map. We document an example of field mapping of geologic contacts in the Canadian Shield, supported by aeromagnetic data, utilizing calculation of a standard edge detector: the horizontal gradient magnitude of the total magnetic field or TF-hgm. Contact locations estimated from this method are accurate enough, sufficiently continuous, and not overly affected by source magnetization and dip, and so provide a solid basis on which the mapping campaign was based and executed successfully.
Summary(Plain Language Summary, not published)
Edge detection is applied to magnetic field data to find locations where there are significant changes in the magnetization of near-surface rocks. These changes have several causes related to the underlying geology - often they represent faults or contacts between different rock types. We discuss practical considerations that should be exercised when using edge detection methods, of which there are many. We show that how the magnetic data were collected has a strong influence over how accurate and reliable the "edge" locations are. We use a recent field mapping campaign to illustrate these concepts.