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Volume 21 Issue 12 (December 2011)

GSA Today

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Article, pp. 4-10 | Full Text | PDF (3.1MB)

Unique geologic insights from “non-unique” gravity and magnetic interpretation

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Richard W. Saltus1*, Richard J. Blakely2*

1 U.S. Geological Survey, MS 964, Denver, Colorado 80225-0046, USA
2 U.S. Geological Survey, 345 Middlefield Road, MS 989, Menlo Park, California 94025, USA


Interpretation of gravity and magnetic anomalies is mathematically non-unique because multiple theoretical solutions are always possible. The rigorous mathematical label of “non-uniqueness” can lead to the erroneous impression that no single interpretation is better in a geologic sense than any other. The purpose of this article is to present a practical perspective on the theoretical non-uniqueness of potential-field interpretation in geology. There are multiple ways to approach and constrain potential-field studies to produce significant, robust, and definitive results.

The “non-uniqueness” of potential-field studies is closely related to the more general topic of scientific uncertainty in the Earth sciences and beyond. Nearly all results in the Earth sciences are subject to significant uncertainty because problems are generally addressed with incomplete and imprecise data. The increasing need to combine results from multiple disciplines into integrated solutions in order to address complex global issues requires special attention to the appreciation and communication of uncertainty in geologic interpretation.

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Manuscript received 18 Aug. 2011; accepted 3 Oct. 2011.

DOI: 10.1130/G136A.1