Approximating edges of source bodies from magnetic or gravity anomalies

Abstract

Cordell and Grauch (1982, 1985) discussed a technique to estimate the location of abrupt lateral changes in magnetization or mass density of upper crustal rocks. The final step of their procedure is to identify maxima on a contoured map of horizontal gradient magnitudes. We attempt to automate their final step. Our method begins with gridded magnetic or gravity anomaly data and produces a plan view of inferred boundaries of magnetic or gravity sources. The method applies to both local surveys and to continent‐wide compilations of magnetic and gravity data (e.g., Zietz, 1982; Simpson et al., 1983a; Kane et al., 1982).

Geophysical interpretations west of and within the northwestern part of the Nevada Test Site

“…The exact locations of the outlines were guided primarily by the maximum horizontal gradients of the magneticpotential or gravity data, which indicate the surface contacts of near-vertical boundaries (Cordell, 1979;Cordell and Grauch, 1985;Blakely and Simpson, 1986). These locations can be offset downdip if the boundaries have shallower dip (Grauch and Cordell, 1987).…”

Evaluation of Aeromagnetic Data of Ilesha Area of Oyo State Nigeria using Analytical Signal (ASM) and Local wavenumber (LWN)

“…At peaks in the local wave number grid, the source depth is equal to n/k, where n depends on the assumed source geometry (analogous to the structural index in Euler deconvolution) for example n=1 for a contact, n=2 for a dyke. Peaks in the wave number grid are identified using a peak tracking algorithm (Blakeley and Simpson, 1986) and valid depth estimates isolated. Advantages of SPI method over Euler deconvolution or spectral depth are that no moving data window is involved and the computation time is relatively short.…”

Assessment of Vertical Magnetic Gradient Data of Tuzla Fault Using Boundary Analysis and 3-D Inversion Techniques

“…When applied to two dimensional surveys, the horizontal gradient tends to place narrow ridges over abrupt changes in magnetization or density. Locating maxima in the horizontal gradient can be done by simple inspection, but [41] automated the procedure with an algorithm that scans the rows and columns of gridded data and records the locations of maxima in a file for later analysis and plotting (Figure 4). …”