The use of curvature in potential-field interpretation*
Jeffrey D. Phillips 1 4 R. O. Hansen 2 Richard J. Blakely 3
1 US Geological Survey, Denver Federal Center, Box 25046, MS 964, Denver, CO 80225, USA.
2 EDCON-PRJ, Inc., 171 South Van Gordon Street, Suite E, Lakewood, CO 80228, USA.
3 US Geological Survey, 345 Middlefield Road, MS 989, Menlo Park, CA 94025, USA.
4 Corresponding author. Email: firstname.lastname@example.org
Exploration Geophysics 38(2) 111-119 http://dx.doi.org/10.1071/EG07014
Submitted: 28 June 2006 Accepted: 27 April 2007 Published: 15 June 2007
Potential-field anomalies can be transformed into special functions that form peaks and ridges over isolated sources. All special functions have a common mathematical form over an isolated source, which leads to a common equation for estimating the source depth from the peak value and the curvature at the peak. Model-specific special functions, usually calculated from a transformed version of a potential field, are used to estimate the locations of very specific source types. Model-independent special functions calculated from an observed or transformed potential field can be used to estimate the locations of a variety of source types. Vertical integration is a particularly useful transformation for reducing the effects of noise and increasing the coherency of solutions from model-independent special functions. For gridded data, the eigenvalues and eigenvectors of the curvature matrix associated with a quadratic surface that is fitted to a special function within 3 × 3 windows can be used to locate the sources and estimate their depths and strikes. Discrete source locations estimated in this manner can be connected into lines that follow contacts, faults, and other mappable features based on distance and azimuth criteria. These concepts are demonstrated on aeromagnetic data from the Albuquerque basin of New Mexico, USA.
Key words: potential-field, interpretation, curvature, source-location, strike.
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