EQUIVALENT SOURCES USED AS AN ANALYTIC BASE FOR PROCESSING TOTAL MAGNETIC FIELD PROFILES

Geophysics ◽  
1973 ◽  
Vol 38 (2) ◽  
pp. 339-348 ◽  
Author(s):  
David A. Emilia
Keyword(s):  
Magnetic Field ◽  
Inverse Problem ◽  
Amplitude Spectrum ◽  
Linear Inverse Problem ◽  
Total Magnetic Field ◽  
Vertical Derivative ◽  
Equivalent Sources

Equivalent sources are useful in processing total magnetic field profiles. A lines‐of‐dipoles distribution, obtained by solving the linear inverse problem, provides an analytic base for computing the following quantities from an observed field: first and second vertical derivative fields, upward‐ and downward‐continued fields, field reduced to the pole, amplitude spectrum of the field, and band‐passed field. A theoretical example demonstrates the validity of the approach, and a field example shows that reasonable results are readily obtained.

Does draping aeromagnetic data reduce terrain‐induced effects?

Geophysics ◽  
1984 ◽  
Vol 49 (1) ◽  
pp. 75-80 ◽  
Author(s):  
V. J. S. Grauch ◽  
David L. Campbell
Keyword(s):  
Magnetic Field ◽  
Magnetic Behavior ◽  
The Other ◽  
Aeromagnetic Data ◽  
Total Magnetic Field ◽  
Vertical Derivative ◽  
Topographic Features ◽  
Other Hand ◽  
Terrain Effects ◽  
The Difference

Contrary to intuition, draped aeromagnetic surveys (when compared to typical level surveys) amplify, rather than reduce, the problem of magnetic‐terrain anomalies. Calculations of the total magnetic field of various simple magnetic topographies on level and draped surfaces support this conclusion. In cases where draped surfaces are lower than level surfaces, the draped profiles exhibit steeper gradients and deeper polarity lows over topography than do the level profiles. On the other hand, where draped surfaces are higher than level surfaces, all anomalies are attenuated, so that magnetic‐terrain effects might be reduced relative to subsurface sources (depending upon the magnetization of each). The difference in magnetic behavior between level and draped data can be explained by a contribution of a vertical derivative component in the draped case that is absent in the level case. The contribution is most significant near topographic features because both the observation surface and the topographic surface are changing vertically.

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