Least-squares Minimization Approaches to Interpret Total Magnetic Anomalies Due to Spheres |
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Authors: | E M Abdelrahman T M El-Araby K S Soliman K S Essa E R Abo-Ezz |
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Institution: | (1) Geophysics Department, Faculty of Science, Cairo University, Giza, Egypt |
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Abstract: | We have developed three different least-squares approaches to determine successively: the depth, magnetic angle, and amplitude
coefficient of a buried sphere from a total magnetic anomaly. By defining the anomaly value at the origin and the nearest
zero-anomaly distance from the origin on the profile, the problem of depth determination is transformed into the problem of
finding a solution of a nonlinear equation of the form f(z)=0. Knowing the depth and applying the least-squares method, the magnetic angle and amplitude coefficient are determined
using two simple linear equations. In this way, the depth, magnetic angle, and amplitude coefficient are determined individually
from all observed total magnetic data. The method is applied to synthetic examples with and without random errors and tested
on a field example from Senegal, West Africa. In all cases, the depth solutions are in good agreement with the actual ones. |
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Keywords: | Magnetic interpretation sphere model least-squares method |
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