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| Titel |
Separation of induced and remanent anomalies through analyses of multiple aeromagnetic surveys |
| VerfasserIn |
Karl Fabian, Marco Brönner, Odleiv Olesen, Suzanne A. McEnroe |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250055434
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| Zusammenfassung |
| Repeated high-quality aeromagnetic surveys have the intriguing potential to separate the
purely induced component from the purely remanent component of the magnetic anomalies.
This is possible in cases where the geomagnetic field has substantially changed between the
two surveys A and B due to secular variation. By upward continuation of both surveys to a
common grid, the anomaly F of the two data sets consists of a remanent part R and an
induced part ÏHA,B
FA = |R + ÏHA |, F B = |R+ Ï HB |, the
difference FB -FA mainly results from the magnetization induced by the secular variation
ΔH = |HB -HA|. In many places of the world the secular variation during the last 20 years
has been more than 500Â nT, giving a sufficiently high signal-to-noise ratio in the difference
of two high-quality aeromagnetic surveys. In this case it is possible to map the approximation
of Ï given by
FB - FA -ΔH.
Moreover, one can obtain estimates of R by combining Ï with the IGRF values of HA,B.
This makes it possible to identify positive remanent magnetic anomalies in crustal rocks, a
topic of high relevance with respect to mineral exploration and lamellar magnetism. The
method is tested using case studies on high-latitude aeromagnetic surveys from Norway and
the Norwegian shelf, which were acquired in the same geographic area with a minimum time
difference of 15 years. An analogous technique may be applicable to analyze the crustal field
using repeat measurements from low-orbit CHAMP and the forthcoming SWARM satellite
missions. |
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